GLOSSARY OF . ENVIRONMENTAL TERMS(TERRESTRIAL)everyspec.com/MIL-STD/MIL-STD-1100-1299/download.php?... · Glossary of Environmental Terms (Terrestrial) 1. SCOPE The terms included

*. >:b

MlL-STD-l 16525 MARCH 1968

MILITARY STANDARD

GLOSSARY OF

. ENVIRONMENTAL TERMS(TERRESTRIAL)

SECONO PRINTING: Any previous issue of thisdocument which is not identified as the “secondprinting” should be withdrawn and destroyed.

●

Downloaded from http://www.everyspec.com

MlL-STD-l 16525 MARCH1968

DEPARTMENTOF DEFENSE

waihill@Oll, D. c. 20301

Glossaryof

Environmental Terms (Terrestrial)

MIL4TD-1166

1. This Military Standard IS mandatory for uae by all Departments and Agencies of the, Department of Defense. i

2. Recommended corrections, additions, or deletione should be adt!reeeed to the Com-manding General, U.S. Airny Natick Laboratories, Attention: AhixRE.E, Natick, Mawa-dqwetts 01760.

n●


.- ,

MIL4TD-1 16525 M4RCH 1968

FOREWORD

1. The purpow of this Gloeaary is to facilitate the ‘xxchange of information wit.hh thebroad field of environmental engineering, by p roviding a common vocabulary for use in thisfield. It is intended primarily for engineers, technicians, and administrators of the Depart-ment of Defense and its contractors, who are engaged in developmental and teeting activi-ties involving any aspect of tbe terrestrial environment but who are not speciaIiste in thesciences that treat these subjecte. A secondary but important purpose is to suggest a selectedetandard terminology for environmental scientists within the Department of Defense.

2. Preparation of this Glossary by the U. S. Army Natick Laboratories was authorizedby letter from the Office of tbe Aeaietant Secretary of Defense, dated 24 May 1965, estab-lishing Project MISC-0346.

9. Contribution by the Weapons Engineering Standardiaation Otlh%, Naval Air Engi-neering Center, under former Project MISC. 0014, are acknowledged, es are the many con-structive comments submitted by agencies tba t reviewed various drafte of the Glossary.

4. Appreciation is expressed to the American Society of Agronomy, the Colorado Sci-entific Society, John Wiley and Sons, Inc., McGraw-Hill Book Company, Inc., the Society ofAmerican Foreetere, and the United States of America Standards Institute, for permissionto quote copyright material from sources cited in the Appendix.

5. The rapidly changing state of the art and the multiplicity of disciplines included inthe environmental eciencea make it essential that some degree of flexibility be exercised inenforcing the use of this document.

6. Users are requested to submit to the preparing activity new terme and definitionsthat have been officially adopted by an agency of the U. S. Government or by a professionalorganization. It is requested that submissions be accompanied by citations of appropriateglossaries or other published sources.

Ill


Paragraph

1.

2.

3.

10.

10,1

10.1.1

10.1.2

10.1.3

‘

MlL-STO-l 16525 MARCH1968

CONTENTS

P.ge

SCOPE ............................................ ...........................................................................

REFERENCED DOCUMENTS ............................................... .............................

DEFINITIONS ..........................................................................................................

Explanation

,.

APPENDIX

4of source9 .............. .............................................. .......................

Bibliography ............................ .......................................................................

1

2

3

....146

....146

Principal Department of Defense sources ........................................................l46

Other

Other

Iv


I .-

,..,

,-“@

,’0

MlL-STD-l 1652S MARCH1968

Glossary of Environmental Terms (Terrestrial)

1. SCOPE

The terms included in this Glossary refer toenvironments on the land surfaces of theearth and adjacent portione of the oceans andlower atmosphere that have a direct effect onsurface conditions. For terms ueed in describ-ing upper atmospheric and space environ-ments, ace the Air Force Glossary of Stand-ardized Terms and Def7nitiorra and the NASADictionary of Technical Terrnz for A erospaceUse, listed’ in the Appendix. Similarly, anauthoritative gfoszary for marine environ-ments is the Glossary of Oceanographic Termsissued by the U. S, Naval OceanographicOffice. The Glossary of Meteorology is theaccepted standard for terms relating to atmos-pheric phenomena, except for deftitions thathave been moditied in official publications ofDefense agencies, such se the Handbook ofGeophysics and Space Environments.

In order to establish a consistent basis fordeeisions as to what terms should be includedor omitted, certain criteria were establishedafter consultation with representatives ofprospective using agencies. It was decided toinclude the following general classes of termsin ;he Military Standard: (1) environmentalterms that have been standardized by theDepartment of Defense; (2) terms used indescribing any aapect of the environmenthaving a direct effect on men or machines;(3) names of sciences concerned with sig-nificant aspects of environment; (4) unitsused in measuring environmental phenomena(except as noted below) ; (5) abbreviationsof terms commonly used in measuring ordescribing environmental phenomena withina particular field (e.g., A, d. b.h.) ; (6) termsused in describing specific effects of the environment on materiel (e.g., atligatoring ) ;and (7) names of general claases of instru-ments or other devices that are used instudying and measuring environmental phe-nomena (but not minor variants or brand

●names of ~uch instruments),

There has been no attempt to make thisdocument a comprehensive glees.ary of sci-ence or technology, of which there are ade-quate representatives already in existence(see Appendix). Rather, all terms consid.ered were screened for rekrvance to environ-mental reeearch or engbuxrkrg, and suchrelevance was the first test for their inclusion.In addition, it was decided to omit the fol-lowing classes of terms, for which the readeris referred either to a standard dictionary orto one of the specialized glossaries .Iisted inthe Appendix: (1) terms that are likely tobe encountered only by users who are special-ists in the field to which the term appliea;(2) terms that are common to science in@neral or to a number of sciencw (for ex-ample, millimeter is omitted because it is aunit of measurement common to many sci-ences, but angstrom is inehsded as a unitused chiefly in radiometry; likewise, generalscientific terms such as theoW, atom, andenergy are not included) ; (3) foreign termsand localisms, unlew they have been adoptedas a generic term in acienti,fic usage (for ex-ample, Santa Ana ia omitted although foeiwrwind ia included) ; (4) physiological, psy-chological, and medical terms, even when theyrefer to a direct effect of environmental phe-nomena; (5) terms used in discussing thetheory of a specialized field, which requirelengthy explanation to be meaningful to thenon-specialist; (6) military terms that pr-tain to materiel, organization, or operationsnot directly related to the environment; and(7) trade names and copyrighted words.

Many worda are used in different senses invarious technologies and contexts, and not allof these usages are appropriate for inclusionin t~]a Glossary. In cases where tids mightcause confusion, detlnitiona that reflect spe-cialized usages are identified by the name ofthe field to which they apply. It will be under-stood that inclusion of a definition in thisGloeaary doea not prejudice the use of a de-fined word in other senses in other contexts.For example, the definition given for sound

1


does not preclude the use of this term in alandforrns context or as an adjective mean-ing “free from defecrs.”

At any one time and place there is only oneenvironment, consisting of the sum total ofexternal conditions affecting material, equip-ment, men, or other organisms. This environ-ment comprises a large number of compo-nents or elements, some of which are nattsral,occurring independently of any human ac-tivities, while others are induced by the actionof machinea or other man-made devices. Thesame element may be natural in some situa-tions and induced in others; for example,wind resulting from a pressure gradient inthe atmosphere is natural, while wind re-sulting from the motion of a vehicle is in-duced.

Natural environmental factors include cli-matic elements such as solar radiation, rain-fall, and free-air temperatures; surface typessuch as sand and rock; terrain features suchaa mountains and plains; biological entitiessuch as individual plants and animals as wellas foresta and other complex assemblages oforganisms; and sporadic occurrences such aslightning and earthquakes. Most of these fac-tors can be altered or reproduced artificially,but only on a vastly smaller scale than theiroccurrence in nature.

On the other hand, certain environmentalfactors are characteristically y associated withthe operation of machines or other man-madedevices. Exam~lea of these induced factorsinclude mechanical shock, exhaust fumes,acoustical and mechanical vibration, nuclearradiation, and bleat effects. Environmentswh]ch are associated with the operation ofparticular weapons, vehicles, or other kindsof equipment may be characterized by par-ticular induced factors and are thereforetermed operational environments. It is notuncommon to find an operational environ-ment within an environmental complex thatis essentially natural. Thus within an aircraftthere may be a distinctive environment in-

cluding induced conditions of pressure, tem-perature, sound, vibration, etc., while outsidethe conditions are largely natural. Even the

●environment outside the aircraft may have “induced elements, however, such as smog,wind resulting from motion, radio waves, andpavement on a runway,

This Glossary includes terms commonlyused in describing and studying both naturaland operational environments. Because of theimpossibility of drawing a sharp line betweenthe natural and induced factors, no attempthas been made to distinguish between themor to identify them separately in the Glossary.

2. REFERENCED DOCUMENTS

The definitions in this Glossary reflect, tothe mayimum extent possible, usage that hasalready been standardized within the Depart-ment of Defense. Definitions of environmen-tal terms that appear in current editions ofthe Dictionary of United States MilitaryZ’er?ns for Joint Usage (JD), or official glos-saries of the Army, Navy, or Air Force, are @quoted verbatim in this Glossary and theirsourcfx are identified in parentheses afterthe definitions. (The letters used to identifysources are explained in the list of referencesin the Appendix.) Terms for which defin-itions have not been standardized within theDepartment of Defense are defined accordingto usage that has been adopted by other Gov-ernmental agencies or by professional organi-zations, to the extent that these organizationshave adopted official glossaries that includesuitable definitions. Definitions from suchsources are quoted in their entirety for someterms, while for others the original sourcemay include explanatory material, additionaldetail, or alternate meanings that were notconsidered essential in the Military Standard.Where the original has been abridged or para-phrased, the source symbol has been markedby an asterisk, and users requiring additionalinformation are referred to the originalsource as listed in the Appendix. Also givenin the Appendix is a third list of references,

2●


. . ,

“m primarily for terms that are not in this Glos-sary or for alternative meanings that are notgiven here.

3. DEFINITIONS

Terms shown in capital letters in the defi-nitions herein are defined elsewhere in theGloesary. Terms shown in italic representalternative usage or subordkate variants not


separatdy defined.

Compound terme are generally listed in theform that is customarily ueed. The invertedform (wg., CHAMBER, ALTITUDE) isused when it is considered desirable to plscetwo or more related terms together ,for readycompsrieon. Direct and inverted forms ofcompound terms are not cross-referenced inthis Glossary.


,, ,

A

A (or A), — Abbreviation for ANGSTROM.

AA, n. — Rough, acoriaceous lava; con.trasted with PAHOEHOE.

ABC SOIL —PedoZugy. A soil with a dis-tinctly developed profile, including A, B,and C horizons. See SOIL HORIZON.(sss)

ABLATION, n. —MeteoroL The combinedprocesses (such es sublimation, melting,evaporation) which remove snow or ice fromthe surface of a glacier, snowfield, etc.; inthis sense, the om.wsite of ahnentation.(AMS)* ‘“

ABLATION AREA — That portion of aglacier below the FIRN LINE, where abla-tion exceeds accumtdation. (AMS)

ABRASION, n. — The process of rubbing,grinding, or wearing away by friction.

ABSOLUTE HUMIDITY — In a system ofmoist air, the ratio of the mass of watervapor present to the volume occupied bythe mixture; that is, tbe density of thewater vapor component. (AMS) *

ABSOLUTE MAXIMUM (MINIMUM)TEMPERATURE — The highest (low.eat) temperature recorded during the pe-riod of record at a stition.

ABSOLUTE RANGE OF TEMPERATURE— The difference between the highest andlowest temperatures on record at a station.

ABSOLUTE TEMPERATURE SCALE —The KELVIN TEMPERATURE SCALE,a scale for measuring temperature fromABSOLUTE ZERO independent of themokcular motion and bedy heat of asubstance.

ABSOLUTE ZERO — The zero point of theABSOLUTE TEMPERATURE SCALE(zero degree KELVIN), of fundamental

● Definition paraphrased, or source not quoted en-tirely.

MlL-ST&l 16525 MARCH1968

significance in thermodynamics. It maybe interpreted as the temperature at whichthe volume of a perfect gas would vanish.The value of absolute zero in degreesCELSIUS is –273.15, by definition.(AMS) ●

ABSORBED DOSE — The quantity of en-ergy acquired by a mass of material ex-posed to RADIATION. The unit ofmeasurement is the RAD.

ABSORBENT, n. — A substance, material,or solution able to imbibe or “attract intoits mass” or trap Iiquide or gases, com-monly used to remove them from a givenmedium or region.

ABSORBER, n. — In general, a medium,aubetance, or functional part that takesup matter or energy. In radwtion andparticle physics, an absorber is a body ofmaterial introduced between a source ofradiation and a detector to determine theenergy or nature of the radiation; toshield the detector from radiation; or totransmit eeleztively one or more com-ponents of the radiation, so that the radia-tion undergoes a change in ita energyspectrum. Such an abeorlx?r may functionthrough a combination of processes of trueabsorption, scattering, and .40wingdown.

ABSORPTANCE, n.— The ratio of the ra-diant flux absorbed in a body of materialto the radiant flux incident upon it. Com-monly, the material is in the form of aparallel-sided plate and the radiation inthe form of a parallel beam incident nor-mally on the surface of the plate. Theabsorptance may be measured for anyradiation, for visible Iight (optical ab-sorptance), or a function of the wavelength of the radiation (epectralabaorptance).

ABSORPTION, n.— 1. The procese wherebythe total number of particles emergingfrom a body of matter ie reduced relativeto the number entering, as a result ofinteraction of the particlee with the body.2. The process whereby the kinetic energy

5



of n particle is reduced while traversinga body of matter. The loss of kineticenergy of corpuscular radiation is alsoreferred to as moderation, slowing, orstopping. 3. The process whereby some orall of the energy of sound waves orelectromagnetic radiations is transferredto the substance on which they are inci-dent or which they traverse; 4. The proc-ess of “attraction into the mass” of onesubstance by another so that the absorbedsubstance disappears physically. 5. Hydrol.The entrance of water into the soil orrocks by all natural processes. It includesthe infiltration of precipitation or snow-melt, gravity flow of etreams into thevalley alluvium, into sinkholes or otherlarge openinga, and the movement ofatmospheric moisture. (MH )

ABSORPTION COEFFICIENT — 1. As ap-plied to radiation (electromagnetic andcorpuscular), a measure of the rate ofdecrease of a beam of photona as a resultof absorption by the material in whichthe radiation is propagating. 2. The ratioof the sound energy absorbed by a sur-face of a medium (or material) exposedto a sound field (or to sound radiation) tothe sound energy incident on the surface.

ACCELERATION, n.— 1. In mechanica, achange in the velocity of a body, or therate of such change, with respect to speedor direction, or both. (NASA) 2. In a morerestricted sense but more popular usage,the act or process of moving, or of caus-ing to move, with increasing speed; thestate or condition of so moving. (NASA)

ACCELERATION OF GRAVITY — Theacceleration produced by the force of grav-ity at the surface of the earth, whichvaries with the latitude and elevation ofthe point of observation. By internationalagreement, the value 9.80665 m/sec2 hasbeeu chosen as the standard accelerationdue to gravity for observation at 45° N.Lat. and sea level. (1S0) *

ACCELERATION, EQUIVALENT STATIC

— An approximate expression ofmum acceleration obtained from a

maxi-shock

spectrum of an assembiy of singi+degree-of-freedom systems as a result of shockexcitation, when expressed as a functionof frequency. ( 1S0)”

ACCELEROMETER, n.— A TRANSDU-CER that senses and responds to accele-rative forces., for measuring, indicating, orrecording such forces. (NASA ) *

ACCLIVITY, n.— An ascending slope, asopposed to DECLIVITY. (GS )

ACCUMULATION, n.— The snow andother solid precipitation deposited on aglacier or snowfield; the quantity de-posited. (ADT)

ACID SOIL — Pedology. Soil with a pHvalue leas than 7.0. For most practical pur-poses a soil with a pH value less than 6.6.The pH values obtained vary greatly withthe method, used and, consequently, thereis no unanimous agreement as to whatconstitutes an acid soil. (The term isusually applied to the surface layer or tothe root r.one unless specified otherwise. )(sss)●

ACOUSTIC (ACOUSTICAL), adj. — Con-taining, producing, arising from, actuatedby, related to, or assmiated with sound.Acoustic is used when the term beingqualified designates something that hasthe properties, dimensions, or physicalcharacteristics associated with sound;acoustical is used when the term beingqualified does not designate explicitlysomething that has such properties, di-mensions, or physical characteristics.(ASA)*

Note 1: The following examples qualify ashaving the ‘-properties or physical charac-teristics associated with sound waves” andhence would take woustic: impedance, in-ertance, load (radiation field) output (soundpower), energy, wave, medium, signal, con-duit, absorptivity, transducer.Note z: The following examples do nothave the requisite physical characteristicsand therefore take acov.atic.zl: society,

6


● method, engineer, schcd, glossary, symbol,problem, measurement, point of view, end-uae, device.Note $: As illustrated in the prscedingnotus, usually the generic term is moditlcdby acoustical, whereas the specific tcchniwdimplication calls for acomtic.

ACOUSTIC NOISE — Any undesired sound.The frequencies involved include at leastthe hand from 15 cycles per second (cps)to 20,000 CPS. (See NOISE).

ACOUSTICS, n.— The science of sound, in.eluding its production, transmission, andeffects. (ASA)*

ACOUSTIC VELOCITY — The speed ofsound or similar pressure waves throughthe atmosphere.

ACOUSTIC WAVE VELOCITY — A VW-tor quantity that sp-ecifies the speed anddirection with which a sound wave travelsthrough a medium. Sonic gpeed is some-times used to describe the speed of a bodywhen it is equal to the acoustic wave

●velocity in the medium in which the bodyis moving.

ACTINIC, adj. — Pertaining to electro-magnetic radiation capable of initiatingphotochemical reactions, as in photog-raphy or the fading of pigments. Beeauseof the particularly strong action of ultra.violet radiation on photochemical proc-esses, the term has come to be almost syn-onymous with sdtraviotet, as in “actinicrays.” (AMS)

ACTINOMETER, n.— The general namefor any instrument used to measure theintensity of radiant energy, particularlythat of the sun. Actinometers may beclassified, accord]ng to the quantitieswhich they measure, in the following man-ner: (a) p~rheliometer, which measuresthe intensity of direct solar radiation; (b)?]yranometer, which measures global ra-diation (the combined intensity of directsolar radiation and diffuse sky radiation) ;and (c) p~rgeometer, which measures theeffective terrestrial radiation. (See RA-

●D1OMETER) (AMS)

7

ML-ND-I 16525 MARCH1968

ACTIVE LAYER — 1. Annually thawedlayer. Layer of ground that thaws in thesummer and freezes again in the winter.(AD) 2. Equivalent to seasonally frocenground. (AD)

ACTIVE ZONE — Equivalent to annual ex-tent of the ACTIVE LAYER. (AD)

ADAPTATION LUMINANCE – The averageluminance (or BRIGHTNESS) of thoseobjects and surfaces in the immediate vi-cinity of an observer estimating the visualrange. Also called adaptation brightness,adaptation illuminance, brightness level,field brightness, jield luminance. CAMS)”

ADFREEZING, n.— The process by whichtwo objects adhere to one another becauseof the binding action of ice. (ADT)

ADIABATIC PROCESS – A thermodynamicchange of state of a system in which thereis no transfer of heat or mass across theboundaries of the system. In en adiabaticprocess, compression always results inwarming, expansion in cooling. In meteor-ology the adiabatic process is often alsotaken to be a reversible process. (AMS)*

ADSORPTION, n.— The adherence of mole-cules of dissolved substances (gases orliquids) to the surface with which theyare in contact, thereby reducing the quan-tity of fluid in the original substance.

ADVECTION, n. — Meteorol. The process oftransport of an atmoepbenc property solelyby the mass motion of the atmosphere;also, the rate of change of the value of theadvected property at a given point. Regard-ing the general distinction (in meteorolo-gy) between advection and convection, theformer describes the predominantly hori-zontal, large-scale motions of the atmos-phere while convection deacribee the pre-dominantly vertical, locally induced mo-tions. (AMS) *

ADVECTION FOG-Fog rasulting from themovement of moist air over a cold surfaceand the consequent ,cooling of this air to



below its dew(AMS) *

point. See SEA FOG.

AEROBIC, adj. —l. Having molecular oxy-gen as a part of the environment. (SSS)2. Growing only inthe presence of molecu~Iar oxygen, es aerobic organisms. (SSS)3. Occuring only in the presence of molecu-lar oxygen (said of certain chemical orbiochemical processes such as aerobic de-composition). (SSS)

AERODYNAMICS, n. —That field of dy -namica concerned with the motion of airand other gaseous fluids, or of the forcesacting on bodies in motion relative’to suchfluids. (AFD)

AEROLOGY, n. —The study of the free at-mosphere throughout its vertical extent; asdistinguished from studies confined to thelayer of the atmosphere adjacent to theearth’s surface. Serological investigationsare made directly by means of soundingballoons and aircraft. They are alao madeindirectly by visual observations from theground, including observations of clouds,meteor trails, the aurora, etc. (ND)

AEROMETEOROGRAPH, n. —Instrumentthat records the pressure and temperatureof the air, the amount of moisture in theair, and the rate of motion of the wind. Anaerometeorograph designed to transmit itsrecord by radio from a balloon is called aradio mcteorognrph or RAD1OSONDE.(AD) *

AERONOMY — The physics of the upper at-mosphere; it includes the study of the

composition, physical properties, and chem-ical reactions of the upper atmosphere.(AMS) ‘b

AEROSOL, n.—l. In atmospheric sciences,a colloid suspension of liquid or solid par-ticles in the air, e.g., H.+ZE. Some fogsand clouds are colloidal systems, but onlyif the drop size is small enough (usuallyless than one micron) to allow colloidalstability. (AMS):’ 2. A term used. to de-note a method of packaging in which gas

under pressure, ora liquified gas which hasa pressure neater than atmospheric atordinary temperatures, is used to spray aliquid. In insecticide aerosols, as definedby the U. S. Department of Agriculture,all particles must be less than 50 micronsin diameter, and 8070 (by weight) mustbe less than 30 microns i~ diameter.

AEROSP.4CE, adj. —Of, or pertaining to,theearth’s envelopeof atmosphere and thespace above it; two separate entities con-sidered as a single realm for activity inlaunching, guidance, and control of vehi-cles-which will travel in both realms. (JD)(For other meanings in Air Force usage,we AF. )

AFTERWINDS, n, —\Vind currents set upin the vicinity of an atomic explosion di-rected townrd the blast center and resuitingfrom the updraft following the rise of thefireball.

AGGLOMERATION, n.— In cloud physics,the process in which precipitation particlesgrow by collision \vith and assimilation ofcloud particles or other precipitation par-ticles. (AMS)*

AGGREGATE, n. —Natural or manmadematerial, with rocklike particles rangingfrom 1A to 21/J inches in diameter and withor without sand and artificial binder usedas a subgrade, base, or surface for a road.[Jsually refers to gravel or crushed rock.Sometimes called road meted (in England).

AGGREGATE (OF SOIL) —A single massor cluster of soil consisting of many par-ticles held together, such as a clod, prism,crumb, or granule. (Y.A)*

“AGGRAD.+TION OF PERMAFROST —Growth of PERMAFROST under the pres-ent climate clue to natural or artificialcauses. Opposite to degradation. (.AD)

AGING, n. — .i gradual process involvingphysical change (s) in the properties orcharacteristics of a material which pro-ceeds in a manner predictable chiefly as afunction of time. In addition, the agin~

8


..

process may be accelerated or slowed whenthe material is also subjected to other fac-tors than time, such as high or low tem-perature, ozone, etc. Aging can weaken ordestroy specific properties in a material, or,conversely, aging can enhance the desiredproperties, as in curing lumber.

AGING, ACCELERATED — Exposure ofmaterial to accelerated, simulated climaticconditions by using hot or cold chambers,intense” sprays, continuous light, or otherartificial means.

AGING, ARTIFICIAL — The change of ma-terial exposed to an artificial environment.,as in a test chamber.

AGING, NATURAL — The change of mate-rial exposed in the natural environment.

AGING, UNDISTORTED ACCELERATED—A short-term exposure of an item whichgenerates the same aging effects as therelated long-term natural exposure.

A-HORIZON —Pedology. See ABC SOILand SOIL HORIZON.

AIR, n. – The mixture of gases comprising theearth’s atmosphere. Since the compositionof the atmosphere is slightly variable withrespect to certain components, the term“puresir” hasnoprecise meaning, butitiscommonly used to imply freedom fromnon-gaseous suspensoids (dust, hydro-meters) and also freedom from suchgaseous contaminants as industrialeffluents. (AMS)*

AIRBORNE DUST—Particles of mineraland other substances, usually of silt size,suspended in the air, such as those raisedby operation of equipment over dry, loes-sial terrain, or those resulting from duststorms.

AIRBURST, n.— An explosion of a bombor projectile above the surface, as dis-tinguished from an explosion on contactwith thesurface or after penetration. (JD)

AIR CHECKS—Surface marking and de-pressions caused by air trspped in rubber

MIL-STil 16525 MARCH1968

and plastics during the curing proce~.

AIR CONDITIONING — The artificial con-trol of humidity, temperature, “purity”,and motion of the air within buildings andother enclosed spaces; also the operation ofequipment for such controls. The objectivemay be to secure either maximum humancomfort or the best environment for agiven industrial operation. (AMS)

AIR DENSITY — 1. The ratio of the massof air to the volume occupied by it. In acontinuous medium the density is definedby a limiting process and is a point fmlc-tion. (AMS) * 2. See BALLISTIC DEN.SITY.

AIR DISCHARGE — A form of lightningdischarge, intermediate in nature betweena cloud discharge and a cloud-to-grounddischarge, in which the multibranchinglightning channel descending from a cloudbase doea not reach the ground, but rathersucceeds only in neutralizing the spacecharge distributed in the sub-cloud layer.(AMS) *

AIR-DRY, adj. — The state of dryness (ofa soil) at equilibrium with the moisturecontent in the surrounding atmosphere. Theactual moisture content will depend uponthe relative humidity and the temperatureof the surrounding atmosphere. (SSS)

AIR-DRY, v.t. — To allow to reach equilib-rium in moisture content with the sur-rounding atmosphere. (SSS)

AIR-EARTH CURRENT — The transfer ofelectric charge from the positively-chargedatmosphere to the negatively-charged earth.This current is made up of the air-earthconduction current, a precipitation current,a convection current, and miscellaneoussmaller contributions. Of these, the first isby far the largest. (AMS) ●

AIR LOSS — The loss in weight by an objector substance on exposure to air at roomtemperature for a specified period of time.

AIR MASS — A widespread body of air that

9



is approximately homogeneous in its, hori-zontal extent, particularly with referenceto temperature and moisture distribution;in addition, the vertical temperature andmoisture variations are approximately thesame over its horizontal extent. (AMS ) *

AIR-MASS CLASSIFICATION — A systemused to identify and to characterize thedifferent air masses according to a basicscheme. A number of systems have beenproposed, but the Bergeron classificationhas been the most widely accepted. Inthis system, air masses are designated ac-cording to the thermal properties of theirsource regions: tropical (’T) ; polar (P) ;and less frequently, arctic or antarctic(A). For characterizing the moisture dis-tribution,, air masses are distinguished asto continental (c) and maritime (m) sourceregions. Further classification according towhether the air is cold (k) or warm (w)relative to the surface over which it ismoving indicates the low-level stabilityconditions of the air, the type of mod-ification from below, and is also re-lated to the weather occurring within thesir mass. This outline of classificationyields the foflowing identifiers for airmasses: cTk, CTW, mTk, mTw, @k, CPW,mPk, mPw, cAk, CAw, mA k, mA w; the fastof which is never used. (AMS)*

AIR, MOIST — 1. In atmospheric thermo-dynamics, air that ia a mixture of dry airand any amount of water vapor. (AMS)2. Generally, air with a high relative hu-midity. (AMS) 3. In environmental engi-neering, a mixture of air and condensedor entrained beads of airborne water, spe-cifically air containing water in the liquidstate.

AIR PRESSURE — The static pressure ex-erted by air. Although this is a very gen-eral term, it is best used in cases where alimited volume of air is concerned, aswithin an enclosed space. This term shouldnever be used to denote a dynamic effectsuch as wind pressure. (AMS)’

AIRSPACE, n. – The space above the surfaceof the earth end its appurtenances, such as ●buildings, trees, etc., or a put of suchspace. (ND)*

AIR STABILITY — The condition of the at-mosphere as affected by the gradient of airtempirsture in the vertical direction,which determines the extent of mixing orexchange between air layers at differentaltitudes. (AD )

ALBEDO, n.— The ratio of the amount ofelectromagnetic radiation reflected by abody to the amount incident upon it, com-monly expressed as a percentage. The al-bedo is to be distinguished from the reflec-tivity, which refers to one specific wavelength (monochromatic radiation). (AMS)*

ALBEDOMETER, n.— An instrument usedfor the measurement of the reflectingpower (the albedo) of a surface. A pyran-ometer or radiometer adapted for themeasurement of radiation reflected fromthe earth’s surface is sometimes employedas an albedometer. (AMS) ●

ALGA (PI. ALGAE), n.—’ 1. A thallophytepossessing chlorophyll; includes almoat allseaweeds. (NOO) 2. A plant of relativelysimple structure which grows chiefly inwater, such as the various forms of sea-weed. Algae range in size from a micro-scopic plant, large numbers of which some-times cause discoloration of water, to thegiant kelp which may have a length of morethan 600 feet. (ND) *

ALIMENTATION, n. — Generally, the proc-ess of providing nourishment or suste-nance; thus in glaciology, the combinedprocesses which serve to increase the massof a glacier or snowfield; the opposite ofABLATION, The deposition of snow isthe major form of glacial alimentation. butother forms of precipitation along withsublimation, refreezing of melt water, etc.also contribute. The ad,litional mass uro.duced by alimentation is termed accri”mu-kztion. (AMS) ●

10


f“a

,0

●

ALKALI FLAT — A PLAYA; the bed of adried-up saline lake that is heavily im-pregnated with alkaline salts. (GS)

ALKALI SOIL — 1. A soil with a high de-gree of alkalinity (PH of 8.5 or higher)or with a high exchangeable sodium con-tent (15 70 or more of the exchange capac-ity), or both. 2. A soil that containssufficient alkali (sodium) to interfere withthe growth of most crop plants. (SSS),

ALKALINE SOIL — Any soil that has a pHgreater than 7.0. (See ACID SOIL). (SSS)

ALL-AGED — Applied to “a stand in whichtheoretically trees of all ages up to andincluding those of the felling age are found.(SAF)

ALLIGATORING, n. — A coating failureattributed to improper use or applicationof paints, varnishes, lacquers, and alliedformulations. It is characterized by the for-mation or separation of large surfacecracks and segments in the characteristicpattern resembling the hide of an alligator.

ALLUVIAL CONE (or ALLUVIAL FAN) —A body of alluvium, shaped like a segmentor sector of a low cone, formed where thegradient of a stream valley decreaaeaabruptly, aa where a steep mountain can-yon emerges into an open valley or onto aplain. The surface of an alluvial fan ianormally marked by stream channels andformer channels that radiate from the apexof the cone, at the mouth of the mountaincanyon, in a pattern somewhat like thatof the riba of an open Japanese fan. Theprofile of a large alluvial fan is normallyconcave, the slope decreasing progressivelyaway from the apex.

ALLUVIUM, n.— A general term for alldetrital material deposited permanently orin tranait by streams. It includes gravel,sand, silt, and clay, and all variations andmixtures of these. It is usually applied tothe deposits of streams in their channelsand over their flood plains and deltss, but

MII.-STD-1 16525 MARCH1968

a few writers include material laid downin lakes and estuaries. Unleaa otherwisenoted, alluvium is unconsolidated. (S&V)

ALP, n. — 1. A high, steep-sided mountain.(ADT) 2. In botany, a mountain pastureor meadow between timberline and enow-Iine. (ADT)

ALPHA PARTICLE — A positively chargedparticle emitted from the nucleus of cer-tain atoms during radioactive disintegra-tion. The alpha particle haa an atomicweight of 4 and a positive charge equal inmagnitude to 2 electron charges; h,ance itis essentially a helium nucleus (heliumatom stripped of its two planetary elec-trons). (AMS) *

ALPHA RAY — A stream of alpha particles.(AMS)

ALPINE, adj. — 1. Of, pertaining to, or likethe Alps in Europe. 2. Descriptive of theplants, animals, and ecological aaaociationsof any high mountain region above timber-line, hence alpine heath, alpine meadow,alpiw pasture, alpine fauna. (ADT) * 3.Pertaining to ALPINE TOPOGRAPHY.(ADT)

ALPINE TOPOGRAPHY - Mountainousterrain modified by glaciation to display anassortment of phyaiographic featurea suchas ar6tes, aiguilles, cirques, and U-shapedvalleys. (ADT)

ALTIMETER, n.— An instrument for indi-cating altitude above or below a givendatum, usually the ground or sea level.

ALTIMETER SETTING — The value of at-mospheric pressure to which the scale of apressure altimeter ia set.

ALTITUDE, n. — 1. The vertical &stancebetween a point and a datum surface.(NOO)” 2. The vertical angle between theplane of the horizon and the line to theobserved point, as a star. (NOO) 3. Theheight of an airborne object above theearth’a surface; above a constant-pressuresurface, or abeve mean sea level. (AMS)”

11



AMBIENT, adj. — Surrounding; external;unconfined..,

AMBIENT TEMPERATURE — The temp-erature of the air or other medium e.ur-rounding an object. (NOO)’

AMBIENT VIBRATION — The aWencom-passing vibration associated with a givenenvironment, being usually a composite ofvibration from many sources near and far,(1S0)

AMPHITHEATER, n. — A relatively flatvaliey or gulch-like depression, generallyoval or circular in outline, formed byglaciation in alpine mountains at or nearthe head of drainage. (NAS)

AMPLITUDE, n.— 1. A measure of themagnitude of the maximum deviation fromthe rest position of a parameter. Amplitude

, may be expressed in either a positive ornegative direction, polarity, or sense, de-pending on the parameter. 2. Mechanics.The extent of the force, displacement veloc-ity, or acceleration of a vibration. 3. a.Electricity. The maximum variation or de-parture from the averageof an alternatingcurrent, voltage, charge, or magnetic flux.b. Electronics. The greatest value of analternating radio wave or the like in onedirection, measuring from zero. 4. Themagnitude of the displacement of a wavefrom a mean value. For simple harmonic,complex harmonic, or random waves, theamplitudes of concern may be peak, aver-age, root-mean-square, peak-to-peak, orone-half the mean difference betweenmaxima and minima.

AMPLITUDE, PEAK TO” PEAK — Of anowilIating quantity, the algebraic differ-ence between the extremes of the quantity.Two times the amplitude of a simple bar.monic oscillatory quantity is its peak topeak amplitude, or double amptitcde.

ANAEROBIC, adj. — 1. The absence of mo-lecular oxygen. (SSS) 2. Growing in theabsence of molecular oxygen (such asanaerobic bacteria). (SSS) 3. Occurring

in the absence of molecular oxygen (as abiochemical process). (SSS)

ANALOG, n.— 1. In synoptic meteorology, a ●past large-scale weather pattern whichresembles a given (usually current) situ-ation in its essential characteristi~.(AMS) * 2. Any environmental element orelement-complex which has basic similari-ties to another element or element-complexlocated in a different part of the world.

ANCHORAGE, n.— An area where a vesselanchors or may anchor, either because ofsuitability or designation. (NOO) *

ANCHOR I.CE (Also called BOTTOM ICE)— The very solid film of ice that developson rocks and other obstructions mr thebottom of a stream, lake, or shallow sea,irrespective of its nature of formation.(NOO) *

ANECHOIC ROOM — A room whose bound-aries absorb effectively all the sound inci-dent thereon, thereby affording essentiallyfree-field conditions.

ANEMOMETER, n.— The general name forinstruments designed to measure the speed ●(or force) of the wind. These instrumentsmay be classified according to the meansof transduction employed: those used inmeteorology include the rotation anemom-eter, pressure-plate anemometer, pressure-tube anemometer, bridled-cup anemometer,contact anemometer, cooling-power ane-mometer, and sonic anemometer. (AMS)

ANGEL, n.— A radar echo caused by a phy-sical phenomenon not discernible to theeye. Angels are usually coherent echoesand sometimes of great signal, strength (UPto 40 db above the noise level). They havebeen ascribed to insects flying through theradar beam, but have also been observedunder atmospheric conditions which indi-cate there must be other causes. Studiesindicate that a fair portion of them arecaused by strong temperature and/or mois-ture gradients such as might be found nearthe boundaries of bubbles of especially

12


warm or moist air. They frequently occurin shallow layers at or near temperatureinversions within the lowest few thousandfeet of the atmosphere. (AMS)

ANGLE OF REPOSE — The maximum slopeor angle, measured from a horizontal plane,at which unconsolidated material (soil orloose rock ) remains stable. When exceeded,mass movement by creeping, slipping, orsliding may be expected. Also called cn”tical

slope. (s&v)ANGSTROM, n.— (Abbreviated A or A) A

unit of length used in the measurementof the wave le@h of light, x-rays, andother electromagnetic radiation and in themeasurement of molecular and atomicdiameters. One angstrom equals 10-s cmor 10-+ microns. The wavelength of visiblelight ranges from about 4000 to 7000 ang.stroms; whereas x-ray wavelengths andatomic diameters are of the order of a fewangstroms. The unit is named in honor ofthe nineteenth century Swedish spectro-scopist, A. J. Angstrom. (AMS)

ANNl_L\L FLOOD — The highest peak dis-charge in a water year. (MH )

ANNUAL RANGE OF TEMPERATURE— The difference between the highest andlowest temperatures recorded at a stationin any given year.

ANODIZING, v. part. — Forming a protec-tive coating on a metal surface by anodicoxidation; most frequently applied toaluminum. Generally, anodized coatingsare hard, abrasion resistant, and offerexcellent resistance to corrosion.

ANTARCTIC AIR — A type of air whosecharacteristics are developed in an antarc-tic region. Antarctic air appears to becolder at the surface in all seasons, and atall levels in fall and winter, than arctic air.(AMS) *

ANTIFOULING, adj. — Pertaining to a pro-tective coating, usually containing coppercompounds such as cuprous oxide or metal-lic copper powder. These are formulated in


a suitable vehicle to provide a toxic en-vironment which retards or prevents thegrowth of barnacles and other marineorganisms on the underwater hull ofwesselsor other objects submerged in sea water.water.

ANTINODE, n.— A point, line, or surfacein a STANDING WAVE where some char-acteristic of the wave field has maximumamplitude. (SVH)

ANTIRESONANCE, n.— A phenomenon ofa system of forced oscillation wherein anychange, however small, in the frequencyof excitation causes an increase in theresponse. (SVH)

APOGEAN TIDAL CURRENT — A tidalcurrent of decreased speed occurring at thetime of APOGEAN TIDE. (NOO)

APOGEAN TIDES — Tides of decreasedrange occurring when the moon is nearapogee. The range at this time is calledapogean range and usually does not occuruntil 1 to 3 days after the moon reachesapogee. (?JOO) *

APOGEE, n.— The point at which a missiletrajectory or a satellite orbit is farthestfrom the center of the gravitational fieldof the controlling body or bodies. (JD)

APPARENT HORIZON — The visible lineof demarcation between land/sea end sky.(JD)

APPLIED CLIMATOLOGY — The scientificanalysis of climatic data in the light of auseful application for an operational pur-pose. “Operational” is interpreted as any ,special ized endeavor, within such as in-dustrial, manufacturmg, agricultural ortechnical pursuits. This is the general termfor all such work and includes agriculturalclimatology, aviation climatology, bio-climatology, industrial climatology, andprobably others. (A MS)

APPLIED ENVIRONMENTAL RE-SEARCH — The collation of statistical,meteorological, climatic, and geographical

13



data, the interpretation of these data, andthe presentation of the evaluated informa-tion in suitable form for application to lo-

t gistics problems of equipment, perqonneland operational functions, and as an sidto designers of military equipment,

APPLIED METEOROLOGY — The applica-tion of current weather data, analyses, andforecasts to specific practical problems. Itis distinguished from applied climatology,which deals with the similar application oflong-period, statistically treated weatherdata. (AMS)

APPLIED RESEARCH — Application of theresults of basic research to accomplish spe-cific objectives. See also BASIC RE-SEARCH. (JD)

APPLIED SHOCK (SHOCK EXCITA-TION) — Any excitation that, if applied toa system, would produce mechanical shock.The excitation may be either a force appliedto the system or a motion of its support.(1S0)”

APRON, n. — An extensive alluvial depositwith generally low outward slope, essen-tially a mature coalesced series of ALLU-VIAL FANS or a well-developed BAJADA.

AQUATIC, adj. — Growing or living in, orfrequenting, or performing in or on water.

AQUIFER, n. — A water-bearing bed orstratum of earth, gravel, or porous stone.

ARCTIC AIR — A type of air whose charac-teristics are developed mostly in winterover arctic surfaces of ice and snow. Arcticair is cold aloft and it extends to greatheights, but the surface temperatures areoften higher than those of polar air. Fortwo or three months in summer arctic airmasses are shallow and rapidly lose theircharacteristics as they move southward.(AMS)

ARCTIC-ALPINE, adj. — 1. ECOL Pertain-ing to areas above timberline. (ADT) 2.Botany and ZOOLPertaining to the distrib-utional pattern or specific habitat of a plant

or animal in areas above timberline.(ADT)

ARCTIC REGIONS — That portion of thenorthern hemisphere which is character-ized by having an average temperature forthe warmest month of between 32 degreesFahrenheit and 50 degrees Fahrenheit.These areas generally correspond withthose seasonally frozen lands which do notsupport forest vegetation and include theadjacent lakes, seas or oceans. (AD)

ARCTIC ZONE — The area north of the Arc-tic Circle (66”32’N). (AMS) *

AREA OF NORTHERN OPERATIONS —A region of variable width in the NorthernHemisphere that lies north of the 50 de-gree isotherm—a line along which the av-erage temperature of the ,warmest four-month period of the year does not exceed50 degrees Fahrenheit. Mountain regionslocated outaide of this area may be includedin this category of operations providedthese same temperature conditions exist.{AD)

ARETE, n.— An acute and rugged crest ofa mountain range, or a subsidiary ridgebetween two mountains, or of a mountainspur, such as that between two cirques.(GS)

ARIDITY, n. — The degree to which a cli-mate lacks effective, life-promoting mois-ture; the opposite of humidity, in the cli-matic sense of the term. (AMS) *

ARROYO, n.— A deep, usually dry gully orchannel in an arid area. Typically, it is cutin unconsolidated material and has steepvertical walls at least several ‘feet high.See DRY WASH and BARRANCA. (S&V)

ARTESIAN WATER — Ground water thatis under sufficient pressure to rise abovethe level at which it is encountered by awell, but which does not necessarily rise toor above the surface of the ground.

ARTIFICIAL DAYLIGHT—Illumination ofan intensity greater than the light of a full

14


:.”0 moon on a clear night. (The optimum illu-mination is the equivalent of daylight.)(SD)

,0.

ARTIFICIAL ENVIRONMENT — An envi-ronment that exists in a test facility undercontrolled conditions, some elements ofwhich are an imitation of conditions foundin nature.

ARTIFICIAL MOONLIGHT — Illuminationof an intensity between that of starlightand that of a full moon on a clear night.(JD)

Nole: The illumination of starlight is 9 x1P foot candies. The illumination of a fullmoon on a clear night is 2 x 10-: foot candles.

ASPECT, n.— 1. The compass direction to-ward which a land slope faces. The direc-tion is taken downslope and normal to thecontours of elevation. (AMS) 2. The grossphysical appearance of a plant type. (SAF)3. The seasonal appearance of a formation,for example, the spring aspect. (SAF)

ASSOCIATION, — Ecot. An assemblage ofplants, usually over a wide area, that haaone or more dominant species from whichit derives a definite aspect.

ATMOMETER, n. – The general name for an [instrument which measures the evapora-tion rate of water into the atmosphere.Four main classes of atmometers may bedistinguished: (a) large evaporation tankssunk into the ground or floating in water;(b) small evaporation pans; (c) porousporcelain bodies; and (d) porous paperwick devices. (AMS) *

ATMOSPHERE, n. — 1. Meteorol. The en-velope of sir surrounding the ~rth andbound to it more or leas permanently byvirtue of the earth’s gravitational attrac-tion. The earth’s atmosphere extends fromthe solid or liquid surface of the earth toan indefinite height, its density asymptotic-ally approaching that of interplanetaryspace. (AMS) * 2. Physh. A unit of pres-sure equal to 101,325 newtons per squaremeter (14.70 pounds per square inch), rep-


resenting the atmospheric preazure of meansea level under standard conditions.

ATMOSPHERE, STANDARD — A hypo-thetical vertical distribution of atmospherictem~rature, pressure, and density which,by international agreement, is taken to berepreaentatite of the atmosphere for pur-poses of pressure altimeter calibrations,aircraft performance calculations, aircraftand missile design, ballistic tables, etc. Thecurrent standard atmosphere ia that whichwas adopted on 15 March 1962 by theUnited States Committee on Extension tothe Standard Atmosphere (COESA). TheU. S. Standard Atmosphere, 1962, up to 32km, haa been adopted by the InternationalCivil Aeronautical Organization (ICAO).(AMS) *

ATMOSPHERIC ACOUSTICS — The studyof (a) sounds of meteorological origin and(b) the role of the atmosphere in the propa-gation of sound. Examplcx of sounds ofmeteorological origin are thunder and anyof the varied aeolian sounds, such se tbehumming of telegraph wires or the mur.munng of trees when winds are blowing.The atrnoaphere influences the propagationof sound in many ways; the velocity ofsound in the atmosphere is governed by theair temperature and by ita molecular com-position; sharp inversions may prcducemarked sound reflection; strong tempera-ture gradients yield sonic refraction; smallturbulent eddies may cause diffraction andscattering of sound that results in acousti-cal scintillation. (AMS)

ATMOSPHERIC DENSITY — The ratio ofthe mzaa of the atmosphere (or any part ofit) to the volume occupied by it. This ratiois grc@eat at sea level and decreases withincreasing altitude; it also may vary hori-zontally depending on conditions of AT-MOSPHERIC TEMPERATURE and AT-MOSPHERIC PRESSURE, It is usuallyexpressed in grama per cubic meter, al-though any other unit system may be used.(AMS)*

15



ATMOSPHERIC ELECTRIC FIELD—Aquantitati~e term, denoting the electricfield strength of the atmosphere at anyspecified point in space and time. In areasof fair weather, the atmospheric electricfield near the eai-th’s surface typically isabout 100 volte per meter and is directedvertically in such a sense as to drive posi.tive chargee downward to the earth. Inareas of fair weather this field decreasesin magnitude with increasing altitude, fall-ing, for example, to only about 5 vol~, permeter at an altitude of about 10 km,(AMS) *

ATMOSPHERIC ELECTRICITY—Electri-cal phenomena, regarded collectively,which occur in the earth’s atmosphere.These phenomena include not only suchstriking manifestations as LIGHTNINGand ST. ELMO’S FIRE, but also lessnoticeable but more common effects suchas atmospheric IONIZATION, the AIR-EARTH CURRENT, and other quiescentelectrical processes. (AMS ).*

ATMOSPHERIC OPTICS — The study “ofthe optical characteristics of the atmos.phere and of the optical phenomena pro-duced by the atmosphere and by particlessuspended in the atmosphere, e.g. AERO.SOLS and WATER VAPOR. It includesthe study of refraction, reflection, diffrac.tion, scattering, and polarization of light,but is not commonly regarded as includingthe study of other kinds of radiation.(AMS)”

ATMOSPHERIC PHENOMENON — Ascommonly used in weather observing prac-tice, an observable occurrence of particularphysical (aa oppoeed to dynamic or synop-tic) significance within the atmosphere.Included are all hydrometers (exceptclouds, which are usually considered sep-arately), Iithometeors, igneous meteors,and luminous meteors. From the viewpointof weather observations thunderstorms,tornadoes, waterspouta, and squalls arealso included. The above usage excludessuch “phenomena” as the local or large.

scale characteristic of wind, pressure, andtemperature; it. also excludes clouds, al-though it includes many products of clouddevelopment and composition. In aviationweather observation, atmospheric phe-nomena are divided into two categories:weather and obstructions to vision. (AMS)

ATMOSPHERIC PRESSURE — The pres-sure exerted by the atmosphere as a con-sequence of gravitational attraction ex-erted upon the “column” of air lying di-rectly above the point in question. (AMS) *Pressure is ueually given in millibars(robs), inches of mercury, pounds persquare inch, or pounds per square foot. Itsstandard value at sea level is about 14.7

pounds per square inch (101,325 newtonsper sq. m.).

ATMOSPHERIC RADIATION—1. Electro-magnetic radiation emitted by the atmos-phere. 2. In meteorology, thermal radiation(about 3 to 80 micron wavelengths) emit-ted by, or propagating through, the atmos-phere which interacts with the atmosphereand provides one of the important mechan.isms by which the heat balance of theearth-atmosphere system is maintained;also called long-wave radiation. (AMS)”

ATMOSPHERIC TEMPERATURE — Thedegree of heat or cold in the envelope ofair surrounding the earth as measured onsome definite temperature scale (usuallyCELSIUS or FAHRENHEIT) by meansof any of various types of thermometers.(AMS)*

ATMOSPHERICS, n.—The radio-frequencyelectromagnetic radiations originating,principally, in the irregular surges ofcharge in thunderstorm lightning dis-charges, Atmospherics are heard as a qua-si-steady background of crackling noise(static) in ordinary amplitude-modulatedradio receivers. (AMS) * (See SFERICS)

ATOLL, n,— A ring-shaped organic reef thatis surrounded by the open sea and enclosesa LAGOON in which there is no land abovesea level. (NOO) *


‘9 ATTENUATION, n.— 1. In general, the de-crease in flux density (or power, ampli-tude, intensity, particles, etc. ) with dis-tance from ‘the energy source by any pro-cess; it includes diminution by distance(inverse square law), absorption, scatter.ing, refraction, and diffusion, 2. In atmos-pheric sciences, the decrease in flux of a“parallel beam” of radiation caused by theeffects of the transmitting medium (main.IY absorption and scattering by the atmos-phere); the effect of distance from thesource (inverse square law) is specificallyexcluded. (AMS ) * 3. In vibration mechan.its, resonant response attenuation will oc-cur if a structure or system is detuned, orif resonant damping increases progres.sively with fatigue, or if elastic isolationmedia are inserted. Electrical attenuationis used in the standardization of multichan-nel recording of accelerometer signals, andwith filters for signal conditioning andrandom vibration equalization.

ATTERBERG LIMITS — Measures of soilconsistency for differentiation between ma.terials of appreciable plasticity (clays) andslightly plastic or nonplastic materiala(silk). The measures include the LIQUIDLIMIT, the PLASTIC LIMIT, and thePLASTICITY INDEX. (BR)

AUDIBLE SOUND — Sound containing fre-quency components lying between about 15and 20,000 cycles per second with sufficientsound pressure to be heard.

AUDIO, adj. — Pertaining to frequencies ofaudible sound waves between about 15 and20,000 cycles per second.

AUDIO FREQUENCY — Any frequencycGrreaponding to a normally audible soundwave. Audio frequencies range ‘roughlyfrom 15 to 20,000 cycles per second.(ASA)*

AVAILABLE WATER — The portion of wa-’tar in a soil that can be readily absorbedby plant roots. Considered by most work-ers to be that water held in the soil againsta pressure of up to approximately 15 bars.


(sss)

AVALANCHE, n. — A large mass of snowor ice, or other surface materials, movingrapidly down a mountain slope. (ADT)”

AVERAGE DISCHARGE — In the annualseries of the Geological Survey’s reports onsurface-water supply—the arithmetic av-erage of all complete water years of rec-ord whether or not they are consecutive.Average discharge is not published for lessthan 5 years of record. The term “average”is generally reserved for average of recordand “mean” is used for averages of shorterperiods, namely, daily mean discharge.(MH)

AWASH, adj. & adv. — 1. Tossed about orbathed by wavea or tide. (NOO) 2. A rockexposed or one just bare at any etage ofthe tide between the datum of mean highwater and the sounding. (NOO)

AZIMUTH, n.— Direction expressed as hor-izontal angle usually in degrees or roilsand measured clockwise from north. Thus,azimuths will be true azimuths, grid azi.muths, or magnetic azimuths, depending onwhich north is used. (AD)

AZONAL SOILS — Soils without distinctgenetic horizons. (SSS) *

B

BABBLE, n.— The combined signal consist.ing of a number of interfering signals re-ceived together. (ND)

BACK BLAST — Rearward blast of gaseafrom the breech of recoilless weapons uponthe burning of the propellant charge. It issometimes referred to as breech blast.(AD)

BACKGROUND, n. — Ever-present effectsin physical apparatua above which a phe.nomenon must manifest itself in order tobe measured, “Background” can take vari.ous forms, depending on the nature of themeasurement.

17



BACKGROUND COUNT — The evidence oreffect on a detector of radiation, other thanthat which it is desired to detect, caused byany agency. In connection with health pro-tection, the background count usually in-cludes the radiations produced by naturallyoccurring radioactivity and cosmic rays.(JD)

BACKGROUND LUMINANCE — In visual-range theo~, the luminance (brightnei+s)of the background against which a targetis viewed. In estimating the visual rangeby objects on the horizon, for example, thebackground luminance is that of the skynear the horizon. In the problem of down-ward oblique visual range, the pertinentbackground luminance is that of the earth’ssurface. (AMS )

BACKSHORE, n. — That part of a BEACHwhich is usually dry, being reached onlyby the highest tides, and, by extension, anarrow strip of relatively flat coast border-ingthe sea. (NOO)

BACKWARD SCATTER—The’ scattering ofradiant energy into the hemisphere ofspace bounded by a plane normal to thedirection of the incident radiation and ly-ing on the same side as the incident ray;the opposite of FORWARD SCATTER. Inradar usage, BACKWARD SCATTER re-fers only to that radiation scattered at 180”to the direction of the incident wave.(AMS)*

BACTERIA, n. PI. — Unicellular micro-scopic organisms, simpler and less com-plex in structure than the fungi and onlyobscurely related to other organisms. Theirunicellular form, lack of definite nucleus,and method reproduction by fission re.motely suggest relationship with bluegreenalgae, from which meet are distinguishedby the absence of pigments The absence ofchlorophyll makee it necessary for bacteriato obtain their nutritional requirementsfrom organic sources.

BADLANDS, n.— Terrain produced by ex-cessive erosion of poorly consolidated ma-

terials and characterized by intricate andsharp erosional featuree. Vegetation isscanty or absent and there is a notable lackof coarse detritus. Hills are steep, fur-rowed, and often of fantastic forms. Bad-lands occur chiefly in arid or semiarid cli-matee where the rainfall is concentrated insudden. heavy showers. (S&V) *

BAJADA, n.— A long outwash detrital slopeat the base of a mountain range, resultingfrom the coalescence of alluvial fans. (GS)

BALLAST, n.— Selected materials (usuallycrushed rock that is irregular in ehape,easily tamped, fireproof, well drained, re-sistant to plant growth and evenly distrib-uted) placed on a railroad to hold the trackin proper alinement.

BALL ICE — Small spheres of sea ice, 1 to2 inches in diameter, rounded and shapedby the waves. They are very soft andspongy, and are generally found in beltssimilar to sludge which forme at the sametime. (AMS)

BALLISTIC DENSITY — A representationof the atmospheric density actually en-countered by a projectile in flight expressedas a percentage of the density according tothe standard artillery atmosphere. Thus,if the actual density distribution producedthe same effect upon a projectile as thestandard density distribution, the ballisticdensity would be 100 per cent. (AMS)

BALLISTIC EFFICIENCY — Ability of aprojectile to overcome the resistance of theair. Ballistic efficiency depends chiefly onthe weight, diameter, and shape of the pro-jectile. (AD)

BALLISTIC IMPACT — The impact of abody during or at the end of its ballis-tic flight, i.e., target impact. The impactcaused by the impingement of particles,fragments, bullets or other objects on thetarget after their trajectory i-light throughspace. This type of impact is differentiatedfrom the impacting of components in aweapon system during environmental im.pact tests.

18


BALLISTIC PENDULUM — A type of ac-celerometer calibrator in which the resul-tant velocity of an initially stationary sus-pended mass, to which the accelerometer ismounted, is measured when the mass isstruck by a second suspended mass releasedfrom a predetermined height. (SVH)

BALLISTICS, n.— The science or art thatdeals with the motion, behavior, appear-ance, or modification of missiles or othervehicles acted upon by propellants, wind,gravity, temperature, or any other modifying substance, condition or force. (JD )

BALLISTIC TEMPERATURE — A com-puted constant temperature that wouldhave the same total effect on a projectiletraveling from the gun to the target as thevarying temperatures actually encoun-tered. (AD)

BALLISTIC WIND — Assumed constantwind that would have the same total effecton a projectile traveling from the gun tothe target as the varying winds actuallyencountered. (AD)

BAND. FREQUENCY—In communicationand electronics, a continuous range of fre-quencies extending between two limitingfrequencies. The term may also be appliedto those frequencies which are encounteredin shock and vibration excitation.

BAND, NARROW — The waves containedwithin a relatively small portion of thespectrum. If a narrow band pass filter isused, the intensity at the two cutoff wave.lengths is a certain percentage of the maxi-mum intensity within the interval.

BAND, WIDE — The waves contained with.in a relatively large portion of the spec-trum. If a wide band pass filter is used, theintensity at the two cutoff wavelengths isa certain percentage of tbe maximum irr-tensity within the interval,

BAND WIDTH—The difference between thecutoff wavelengths of a band.

● BAND WIDTH, EFFECTIVE — The band


width of an ideal transmission systemwhich ( 1) has unifom transmission in itapass band equal to the maximum transmis-sion of the specified system and (2) trans-mits the same power as the specified sys-tem when the two systems are receivingequal input signals having a uniform dis-tribution of energy at all frequencies.(SVH)

BANK, n.— 1. An elevation of the sea floorlocated on a continental (or island) shelfand over which the depth of water is rela-tively shallow but sufficient for safe navi-gation. It may support shoals or bars onits surface which are dangerous to naviga-tion. (NOO) 2. In its secondary sense, ashallow area consisting of shifting formsof silt, sand, mud, gravel, etc., but in thiscase it is only used with a qualifying wordsuch as “sandbank,” “gravel-bank,” etc.(NOO) 3. A ridge of any material such asearth, rock, snow, etc., or anything resem-bling such a ridge, as a fog bunk or cloudbank. (ND) 4. The border or shore of ariver. (ND) 5. The margin of a channel.Banks are called right or left as viewedfacing in the direction of the flow. (MH)

BAR, n.— 1. Meteor-oL A unit of pressureequal to 10° dyne per cmz (10E barye),1000 millibars, 29.53 inches of mercury.(AMS) 2. As a coastal Iandform, a ridge ofunconsolidated material lying seaward ofa shore (oflsbore bar). A bar may be sub-merged even at low tide, it may be tidal, orit may rise above high tide level. Most barsconsist of sand or gravel. 3. As a landformin a stream channel, an accumulation ofalluvium, usually ridgelike and elongate inthe direction of the current. Moat riverbars consist of sand (sandbars) or gravel(gravel bars), but some are of mud (some.times called mudbanks ) and some consistof cobbles or even boulders. Many riverbars are emergent at low water, and someare only covered at flood stage.

BARCHAN, n. — An independent, traveling,crescent-shaped dune or drift of wind-blown sand or enow, with the crescent fac-

19


MlL-STD-l 1652S MARCH 1968

,,

ing toward the prevailing winds. A trans-verse type dune, it has an asymmetricaland crested cross-section with a steep in-ner-slope and a relatively gentle outer-elope. Conditions under which barchansform include a relatively small to moderatesupply of material and winds of almostconstant direction and moderate speed.

BARNACLE, n.— A marine crustacean hav-ing feathery appendages (cirri ) for gath-ering food, and found attached to rocks,floating logs, and ships’ bottoms.

BAROGRAPH, n.- A recording barometer.Barographs may be classified on the basisof their construction into the followingtypes: (a) aneroid barograph (includingmicrobarograph), (b) float burogmph. (c)photographic barogmph, and (d) weightbarograph. The aneroid barograph, whichis the least complicated and possibly leastaccurate of the barographs, is the onemeet commonly used in weather stations.(AMS)

BAROMETER, n.—An instrument for mese-

uring ATMOSPHERIC PRES.SURE.(NOO) A mercurial barometer employs a

column of mercury supported by the atmos-phere. An aneroid barometer has a partlyexhausted, thinmetel cylinder somewhatcompressed by atmospheric pressure.

BAROMETRIC CORRECTIONS — The cor-rections which must be applied to the read-ing of a mercury barometer in order thatthis observed value may be rendered ac-curate. There are four kinds. (a) The in-strument correction is the mean differencebetween the readings of a given mercurybarometer and those of a standard instru-ment. It is a composite correction, includ.ing the effects of capillarity, index misa-lignment, imperfect vacuum, and scale cor-rection, which are the barometric errors.(b) The temperature comectiow is appliedto account for the difference between thecoefficient of expansion of mercury andthat of the scale. (c) Tbe gravity conec-tion is necessary because the acceleration

of gravity varies both with altitude andlatitude. (d) The removal correction is ap-plied when the barometer elevation differsfrom the adopted station elevation and/orclimatological station elevation. (AMS)

BAROMETRIC PRESSURE—Atmosphericpressure as indicated by a barometer. Thisatmospheric pressure is the pressure ex-erted by the atmosphere as a consequenceof gravitational attraction exerted upon tbe“column” of air lying directly above thepoint in question. (AMS) *

BAROTH.ERMOHYGROGRAPH, n. An in-strument which automatically records pres-sure, temperature, and humidity of the at-mosphere. (ND)

BARRANCA, n.— A DRY WASH or RA-VINE having stsep sides and a narrow bedless than two meters wide. See ARROYOand WADI.

BARRENS, n.— A relatively desolate area,where vegetation is lacking (as in an ice-cap or desert) or is scanty and is restrictedto a few species, as compared with adja-cent areas, because of adverse soil, wind,or other environmental factors.

BARRIER MATERIAL — A material de-signed to withstand, to a specified degree,penetration of water, oils, water vapor, orcertain gases such as CO! and NZ. Mater.ials are also used as thermal and acousticbarriers.

BARRIER REEF — A coral reef parallel toand separated from the coast by a LA-GOON that is too deep for coral growth.Generally, barrier reefs follow the coastsfor long distances and are cut through atirregular intervals by channels or passes.(NOO)

BASALT, n.— Any one of a group of fine-grained, dark, heavy, widely distributedvolcanic rocks. No strict definition of basaltas a mineralogic type has been agreedupon.

BASE SURGE — A cloud which rolls out

20


.

from the bottom of the column producedby a subsurface burst of a nuclear wesp-on. For underwater bursts the surge is, ineffect, a cloud of liquid droplets whichhas the property of flowing afmost as if itwere a homogeneous fluid. For subsurface land bursts the surge is made upof small solid particles but still behaveslike a fluid. (JD)

BASIC RESEARCH — Efforts directed to-ward an increase in fundamental knowl-edge. See also APPLIED RESEARCH.(JD)

BASIN, n.— 1. A depression of the sea floormore or less equidimensional in form andof variable extent. (NOO) 2. An area in atidal region in which water can be kept ata desired level by meana of a gate. Alsocalled tidal basin. (ND) 3. A relativelysmall cavity in the bottom or shore, usuallycreated or enlarged by excavation, largeenough to receive one or more vessels for aspecific purpose. (ND ) 4. An area of landwhich drains into a particular lake or seathrough a river and its tributaries. (ND)5, The drainage or catchment area of astream or lake. (GS) *

BATHYMETER, n.—An instrument primar-ily designed for measuring depth of water,Bathymetric surveys, previously done bylead line, are now performed by ueing anecho sounder and precision depth recorder.(NOO)

BATTLEFIELD ILLUMINATION ——Thelighting of the zone of action of groundcombat and combat support troope by ar-tificial means other than invisible rays.(JD)

BEACH, n.— 1. The area extending fromthe shoreline inland to a marked changein physiographic form or material, or tothe line of permanent vegetation (coaat.line). (JD) 2. In amphibious operations,that portion of the shoreline designated forlanding of a tactical organization. (JD)3. A gently eloping area of wave-depositedunconsolidated material borderirm a sea or-

21


lake; also, the unconsolidated materialmaking up euch a beach.

BEAT FREQUENCY — Either of the twoadditional frequencies obtained when s“ig-nals of two frequencies are combined, equalto the sum or difference, respectively, ofthe original frequencies. (ND)

BEAUFORT WIND SCALE — A system ofestimating and reporting wind speeda, in-vented in the early nineteenth century byAdmiral Beaufort of the British Navy. Init9 present form for international meteor-ological use it equates (a) Beaufort force(or Beaufort number), (b) wind apeed,(c) descriptive term, and (d) visible ef-fects upon land objects or sea surface. Asoriginally given, Beaufort numbers rangedfrom O, calm, to 12, hurricane. They havenow been extended to 17. (AMS) *

BED, n. — A layer of rock differing fromlayers above and below, or set off by moreor less well marked divisional planes; alayer i! a series of etratitled (sedimen-tary) roeka.

BEDROCK, n. — The more or lew soli~ un-disturbed rock in place either at the surfaceor beneath supertlcial deposita of gravel,aand, or soil. Accord]ng to local conditionsand ueages, bedrock may be soft or hard,consolidated or unconsolidated. (S&V)

BEL, n.— A unit expressing the relation be-tween amounta of signal power and differ-ences in sound-sensation levels. The num-ber of bels is equal to the common logar-ithm of the ratio of the two powers orsound levels involved. Two powers or lev-els differ by one bel when their actual ratiois 10:1. See DECIBEL. (U.S. Army TM11-486-11)

BELGILfM BLOCK COURSE — A test facihity for simulating the conditions of trans-portation. The course is a specially pre-pared road bed having varying degreea ofroughness, waviness, and other controlledcharacteristics over which wheeled equip-ment is moved at varying speeds to etudy

L



the effects of shock and vibration causedby transportation. Belgium Block is onlyone section of the Munson Test Coursewhich also. includes a course washboard, aradial washboard, and a single corrugationsection.

BENCH, n.—A strip of relatively level earthor rock, raised and narrow. A small terraceor comparatively level platform breakingthe continuity of a declivity. (GS)

BERGY BIT, n. —A medium-sized piece ofice, generally less than 5 meters (16.4feet) high and about the size of a smallcottage. It usually originates from glacierice but occasionally from a massive pieceof sea ice or hummocked ice. When it isknown to be sea ice, the term /?oeberg maybe used. (NOO)*

BERM, n.— The nearly horizontal portion ofa beach or backshore having an abrupt falland formed by deposition of material bywave action and marking the limit of ordi-nary high tides. (NOO)*

BETA PARTICLE —A positive or negativeelectron emitted by the nucleus during ra-dioactive transformation; also called betaray. By extension, electrons accelerated toextremely high speeds (kinetic energiesabout one million electron volts or more)are called beta particles.

BEVAMETER, n. — A mobile or portable in.strument developed by the Land Locomo-tion Laboratory for measuring horizontaland vertical stress-deformation curves ofnatural soils or soil simulating materiala,and consisting of one or more rotatinghorizontal shear heads and one or morevertical displacement penetrometers.

B-HORIZON — See SOIL HORIZON.

BIOFOG, n.— Basically, a type of steam fogcaused by contact between extremely coldair and the warm, moist air surroundinghuman or animal bodies or generated byhuman activity. These fogs are sometimesnamed after their specific sources, such asanimal fog, human fog, town fog. (AMS )

BIOLOGICAL AGENT — A microorganism

.

which causes diseaae in man, plants or ani-mals or causes the deterioration of materi-al. (JD)

BLACK BODY — A hypothetical “body”which absorbs all of the electromagneticradiation striking it; that is, one whichneither reflects nor transmits any of theincident radiation. No actual substance be-haves as a true black body, although plati-num black and other soots rather closelyapproximate this ideal (AMS) *

BLACK-BODY RADIATION — The electro-magnetic radiation emitted by an idealblack body; it is the theoretical maximumamount of radiant energy of all wave-lengths which can be emitted by a body ata given temperature. (AMS) *

BLACK-BULB THERMOMETER — Athermometer whose sensitive element hasbeen made to approximate a black body bycovering it with lamp black. The thermom-eter is placed in an’ evacuated transparentchamber which is maintained at constanttemperature. The instrument responds toinsolation, modified by the transmissioncharacteristics of its container. (AMS)

BLACK FROST — 1. A dry freeze, with re-spect to its effects upon vegetation, that is,the internal freezing of vegetation unac-companied by the protective formation ofhoarfrost. A black frost is always a killingfrost, and its name derives from the result-ing blackened appearance of affected vege-tation. (AMS)

BLACKOUT, n.— Radio fadeout due to ion-ospheric disturbances, often accompaniedby a magnetic storm, prevalent in the Arc-tic and Ant&ctic. Also called a@c black-out, polar blackout. (ADT) ●

BLAST, n.— The brief and rapid movementof air vapor or fluid away from a center ofoutward pressure, as in an explosion or inthe combustion of rocket fuel; the pressureaccompanying this movement. This term iscommonly used for “explosion’;, but thetwo terms may be distinguished. (JD)

22


BLAST EFFECT — Destruction of or dam-age to structures and personnel by theforce of an explosion on or above the sur.face of the ground. Blsst effect may be con-trasted with the cratering and groundahcck effects of a projectile or charge whichgoes off beneath the surface. (JD)

BLAST WAVE — A sharply defined wave ofincreased pressure rapidly propagatedthrough a surrounding medium from a cen-ter of detonation or similar disturbance.(JD)

BLINK, n.— A glare on the underside of ex.bmsive cloud areas, created by light re-flected from snow or ice-covered surfaces.Snow blink is whitish and brighter thanthe yellowish-white glare of ice blink.(ND)

BLISTERING, n.— A coating failure cornmon to paints, varnishes, lacquers, and re-lated formulations. It is characterized bythe formation of local or scattered blistersvarying in size from small pimples to largepatches, usually attributed ta surface con-tamination or endo-osmosig of water as theresult of exposure of coatings to excessivemoisture.

BLIZZARD, n, — A eevere weather conditioncharacterized by low temperatures and bystrong winds bearing a great amount ofsnow (mostly fine, dry snow picked upfrom the ground ). The U.S. Weather Bu-reau specifies, for blizzard, a wind of 32mph or higher, low temperatures, and suf-ficient snow in the air to reduce visibj]jtyto less than 500 ft; and for severe blizzard,wind speeds exceeding 45 mph, tempera-ture near or below 10°F, and visibility re-duced by snow to near zero. (AMS) *

BLOCK, n.— 1. Hydrography A sea ice frag-ment more than 6 feet but lees than 30 feetin diameter. (ADT) 2. GemnoWhology. Anelongate or quadrangular, often tilted sec-tion of a faulted part of the earth’s crust,hence block mountaine. (ADT)

BLOOM, n.- A surface coating failure asso-

MIL-STD-1 16525 MARCH1968

ciated with high gloss painta, varnishes,lacquers, and related formulations. It ischaracterized by the formation of a sur-face haze which lowere the original specu-lar gloea, imparting a dull or semiglossappearance to the coating.

BLOW-DOWN — 1. A windfall. (ADT) 2.Trees knocked down as a result of so ex-plosion (e.g., nuclear detonation).

BLOWING DUST — Dust picked up locallyfrom the surface of the earth and blownabout in clouds or sheets. It may completelyobecure the sky; in its extreme form it is adust storm. (AMS) ●

BLOWING SAND-Sand picked up from thesurface of the earth by the wind and b)ownabout in clouds or sheets. In its extremeform, blowing sand constitutes a aandstorm. (AMS ) *

BLOWING SNOW — Snow lifted from thesurface of the earth by the wind to a heightof six feet or more above the surface (high-er than drifting snow), and blown about insuch quantities that horizontal visibility isrestricted at and above that height. Blow-ing snow is one of the classic requirementsfor a blizzard. (AMS)”

BLOWN-OUT LAND — Areas from whichall or almoet all of the soil and soil materialhas been removed hy wind erosion. Usuallybarren, shallow depressions with a flat orirregular floor consisting of a more reeist-ant layer and/or an accumulation of p+?b-bles, or a wet zone immediately above awater table, Usually unfit for crop produc-tion. (SSS) *

BLUFF, n.— A cliff with a broad face, or arelatively long strip of land rising abmptlyabove surrounding land or a body of water.(ND)

BLUSH, v.— Of a dopsd fabric or surface:TO become dull or pale ,x a result of rapidevaporation or high humidity, with a con-sequent weakening of the dope film.(NASA) I

23


MlL-S?D-l 1652S MARCH 1968 ,

BLUSHING, n. — A condition in which acloudy film appeara on a newly lacqueredsurf ace. It is caused direct] y by the pre-cipitation of a portion of the solid contentof the material. This is usually due to oilor water mixed in the lacquer, a relativelyhigh hum’idity condition, of too rapid dry-ing.

BOG, n.— 1. A quagmire or morass j an areaof wet, peaty, spongy ground, usually lacki-ng in mineral nutrients, often interspersedwith pools of open water, where any densebody is likely to sink. (ADT) 2. Botan&.The vegetation of saturated, peaty land inopen or forest areaa; hence moss bog,juncus bog, carex or sedge bog, sphagnumbog, birch bog, tamarack bog, black sprucebog. (ADT) *

BOLE, n.— 1. The stem or trunk of a tree,usually the lower, usable or merchantableportion of the tree trunk. 2. A lump ofearth formed of any of several varietiesof friable clay, usually colored red by ironoxide.

BOLOMETER, n. -An instrument whichmeasures the intensity of radiant energyby employing a thermally-sensitive electn-oal resistor. (AMS) *

BORA, n.— A fall wind whose source is socold that when the air descends to the low-lands or coast the dynamic warming is in-sufficient to raise the air temperature tothe normal level for the region; hence itappears as a cold wind. The terms bw”noand bo~accia denote a weak bora and strongbora, respectively. The term was originallyand still ,is applied to the cold northeastwind on the Dalmatian coast of Yugo-slavia in winter when cold air from Russiacrosses the mountains and descends to therelatively warm coast of the Adriatic. Theterm bora is now applied to similar windsin other pafi of the world. (AMS) *

BORE, n.— A restricted tidal current ofconsiderable force and size. Also called aneagre. (ADT)

DOTTOM, n.— Any ground covered by wa-ter. Bed refers more specifically to the wholesubmerged basin, and floor is the essen-tially horizontal surface of the ground be-neath the water. (NOO )

BOTTOM ICE — See ANCHOR ICE.

BOTTOMING, n.— In shock and vibrationmechanics, the metallic or elastomeric snub-bing of resiliency-mounted devices whereintlie resWnse displacements, under shock orresonant vibration loading, exceed the nor-mal resilient displacement limits, and ap-plied acceleration levels are multiplied.(SVH)*

BOULDER, n. — A piece of rock, separatefrom bedrock, more than 256 mm in maxi-mum dimension. Sometimes considered toaPPIY only to rounded stones of this size.

BOUNCE, n.— 1. A colloquial term used insound recording, implying that reverbera-tion is relatively high for high-frequencycomponents. 2. In shock and vibration me-chanics, a term used to denote repetitiveresonant BOTTOMING.

BOUNDARY LAYER — 1. The layer of fluidin the immediate vicinity of a boundingsurface, referring ambiguously to the lami-nar boundary layer, turbulent boundarylayer, planetary, or surface boundary layer.(AMS) 2. A thin layer of fluid next to thesurface of a bcdy in a moving stream (asan airfoil in an airstream) having distinc-tive flow characteristics as a result of fric-tion between the fluid and the surface of thebody. The flow in lhe boundary Iayer maybe Iaminar, turbulent, or transitional be-tween Iaminar and turbulent. (NASA)

BOURDON TUBE — A closed curved tubeof elliptical cross-section used in some tem-perature-sensing and pressure-sensing in-struments. The expansion of the fluid dueto a temperature change causes an increasein the radius of curvature of the tube. Thecurvature may then k measured by thetravel of the tip of the tube. The curvatureis a measure of the difference between the

24


e pressure inside the tube and that outside.(~lJs):,

Box, n.- See CHAMBER.

BRACKISH, adj. — Containing salt to amoderate degree, such as sea water whichbas been diluted by fresh water, as near themouth of a river. Brackish water has salini-ty values ranging from approximately 0.50to 17.00 parts per thousands. (NOO) *

BRAIDED STREAM — A stream flowing inseveral chrmnels, which divide and reunitein a pattern resembling the strands of abraid.

BRASH, n.— Loose accumulation of frag-ments of sea ice (or fresh-water ice) ; eachpiece is less than 6 feet across and called a“bit” of ice. Sometimes called rubble.

BRASHNESS, n.— An abnormal conditionthat causes some pieces of wood to be rela-tively low in shock resistance for the speciesand, when broken in tlexure, to failabruptly without splintering and at com-

0paratively small deflections. Sometimes as-sociated with fungus attack or short grain.(SAF)

BREAKAWAY, n.— The action of a bound-ary layer separating from a surface.(NASA)

BREAKER, n.— A wave breaking on theshore, over a reef, etc. Breakers may beroughly classified into three kinds, al-though the categories may overlap: (1)Spitting breakers break gradually over aconsiderable distance; (2) Phmging b?eak-erx tend to curl over and break with acrash; and (3) Surging tweakere peak up,but then instead of spilling or plunging theysurge up on the beach face. (NOO) *

BREAKS, n.—An area in rolling land erodedby small ravines and gullies; also used toindicate any sudden change in topography,es fro,m a plain to hilly country. (GS)

BREAKUP, n.—ln general, the spring melt-ing of snow, ice, and frozen ground. Specif.,

●the destruction of the ice cover on rivers

25

MIL-STW1 16525 MARCH 1968

during the spring thaw; or applied to thetime when the solid sheet of ice on riversbreaks into pieces that move with the cur-rent. (ADT)

EREEZE, n.— 1. Wind of force 2 to 6 (4-31miles per hour or 4-27 knots) on the Beau-fort scale. Wind of force 2 (4-7 miles perhour or 4-6 knots) is classified as a Ziflhtbreeze; wind of force 3 (8.12 miles perhour or 7-10 knots), a ~entlc breeze; windof force 4 (13-18 miles per hour or 11-16knota), a rnoder-at~ breeze; wind of force 5(19-24 miles per hour or 17-21 knots) afresh breeze; and wind of force 6 (25-31miles per hour or 22-27 knots), a strongbreeze. 2. Any light wind. A kmd breezeflows from the land to the sea, and usuallyalternates with a sea breeze blowing in theopposite direction. A mountain breeze blowsdown a mountain slope due to gravity flowof cooled air, and a vu[tey breeze blows upa valley or mountain slope because of thewarming of the mountainside and valleyfloor by the sun. A puff of wind, or lightbreeze affecting a small area, may be calleda .cat’e paw. Absence of wind is sometimescalled ash breeze. (ND)

BRIGHTNESS, n. — See LUMINANCE.

BRINE, n.— Sea water containing a higherconcentration of dissolved salt than that ofthe ordinary ocean. Brine is produced bythe evaporation or freezing of sea water,for, in the latter case, the sea ice formedis much less saline than the initial liquid,leaving the adjacent unfrozen water withincreased salinity. The liquid remainingafter sea water has been concentrated byevaporation until salt has crystallized iscalled bittern.

BRISANCE, n.— The shattering effect of anexplosion on materials.

BRITTLENESS, n. — The quality of a mate-rial that leads to crack rmoDa~ation without.-appreciable plastic deformation.

BROKEN ICE — In sea ice reporting,that covers one-half to four-tiftha of

icethe


MlL-STD-l 165 ~~25 MARCH 1948

Im+l sea surface. Also called 100SCice, openice, dzck ice. (ADT)

BRUSH, n. — Shrubs and stands of short,scrubby tree species that do not reach mer-chantable size. (SAF)

BUMP, n.— A mechanical shock of relativelylow magnitude. (1S0) *

BUMP TESTER — A shock machine that iscapable of generating bumps repetitive y.

BURBLE, n. — L A separation or breakdownof the streamline flow pasta body. (NASA)2. The eddying or turbulent flow resultingfrom this. (NASA)

BURIED SOIL — Soil covered by an alluvial,loesaial, or other deposit, usually to a depthgreater than the thickness of the solum.(sss)

BUOYANCY, n. — 1. That property of anobject that enables it to float in a liquid, orascend through and remain freely suspend-ed in a compressible fluid such as the at-mosphere. Quantitatively, it may be ex-pressed se the ratio of the specific weightof the fluid to the specific weight of anobject; or, in another manner, by theweight of the fluid displaced minus theweight of the object. (AMS) 2. The up-ward force exerted upon a parcel of fluid(or an object within the fluid) in a gravi-tational field by virtue of the density dif-ference between the parcel (or object). andthat of the surrounding fluid. (AMS) $

BURN, n. — A section of forest or scrubdevastated by fire; the clearing made byfire. (ADT)

BURST, n. — Increased energy tra@n@ionof brief duration; particularly, ‘increasedradio wave or thermal radiation from thesun, lasting from a fraction of a second toabout a minute. An isolated burst is one oflarge magnitude occurring during a rela-tively quiet period. (ND)

BUSH, n.— M+?teorol. The mass of spray ordense water vapor thrown outward fromthe base of a WATERSPOUT. Also called

bon firs, cuscade. (ND)

BUTTE, n.— An isolated, flat-topped hill or ●mountain with steep sides, smaller than aMESA. Buttes are most common in aridregions.

BUZZ, n. — 1. A rapid vibration or oscilla-tion of a structure or body. (NASA) 2. Thenoise resulting from the rapid vibration oroscillation of a structure or body. (NASA)”

BUZZ, v.— To vibrate or oscillate rapidly,making a humming noise. (NASA)

c

C — Abbreviation for the CELSIUS or CEN-TIGRADE TEMPERATURE SCALE.

CABINET, n.— See CHAMBER.

CABLE EFFECT — In electrical cables usedto transmit TRANSDUCER output signalsto associated instrumentation, the effect ofcable weight and stiffness upon the re-sponse of the measured structure, the in-troduction of electrical noise resulting from ●mechanical cable distortion, and the effectof cable resistance, capacitance, and induct-ance upon the frequency response of thesignal. (SVH)

CALCAREOUS SOIL — Soil containing suf-ficient calcium carbonate (often with mag-nesium carbonate) to effervesce visiblywhen treated with cold O.lN hydrochloricacid. (SSS)

CALDERA, n.— A basin-shaped volcanic de-pression with a diameter many times great-er than that of the included volcanic ventor vents. Many caldersa contain one ormore volcanic cones within them.

CALIBRATE, v.t. — To fix, check, or correcta measuring instrument to agree with areference standard; to STANDARDIZE.

CALICHE, n.— 1. A layer near the surface,more or less cemented by secondary carbon-ates of calcium or magnesium precipitatedfrom the soil solution. It may occur as a soft

e26


‘e

“.@

thin soil horizon, as a hard thick bed justbeneath the solum, or ss a surface layerexposed by erosion. Not a geologic deposit.(SSS) 2. Alluvium cemented with sodiumnitrate, sodium chloride, snd/or other solu-ble salts in the nitrate deposita of Chile andPeru. (SSS)

CALM, n.— The absence of apparent motionof the air. In the Beaufort wind scale, thiscondition is reported when smoke is ob-served to rise vertically, or the surface ofthe sea is smooth and mirror-like. In UnitedStates weather observing practice, the windis reported as calm if it is determined tohave a speed of less than one mile per hour(or one knot). (AMS)

CANOPY, n.— In a forest, the cover ofleaves and branchea formed hy the crownsof all the individual treea. Its density isordinarily expressed ss the amount (or par.centage) of the ground that would be com-pletely covered by the foreat if the sunwere directly overhead.

CANYON, n.— 1. A deep ravine or gorgewith steep sides. (ND) 2. A long narrowsubmarine depression with relatively steepsides. If the sides are more gently sloping,the depression is called a submarine valley.Most canyons penetrate a continental orinsular shelf more or less perpendicularlyto the coast line. Also called subman”necanyon. (ND)

CASCADE, n.—l. The mass of spray thrownout ward from around the base of s WA-TERSPOUT. Also called bonfire, BUSH.(NOO) * 2. A fall of water over steeply

sloping recks. (ND) 3. Disturbed ice of sglacier over a steep incline, called ice cae-cade,’ (ND)

CATARACT, n.— A waterfall, usually ofgreat volume; a cascade in which the verti-cal fall has been concentrated in one sheerdrop or overflow. (GS)

CATENA, n.— Pedo&gy. A sequence of soilsof about the @me age, derived from similarparent material, and occurring under simi-

MIL-STD-1 16525 ,MRCH 1968

lar climatic conditions, but having differentcharacteristics due to variation in reliefand in drainage. (SSS)

CATHODIC PROTECTION — Reduction orprevention of corrosion on a metal by achange of polar qualities by either electri-cal, magnetic or electrostatic means so thatthe surface will repel corrosive oxide pro-ducing material, e.g. by uw of sacrificialanodes or impressed currents.

CAT ICE — Ice, on a body of water, thatremains as an unbroken surface when thewater level drops so that a cavity is formedbetween the water surface and the ice. Alsocalled SHELL ICE. (NOO)

CAVERN, n;— A large natural undergroundcave or series of caves. Often but not al-ways used to imply largeness or indefiniteextent to distinguish from cave.

CAVITATION,’ n. : The formation of localcavities in a liquid or vapor, as a result ofthe reduction of total precsure. For non-degaaaed liquids, these cavities are filledwith the gaaea dissolved in the liquids andare produced whenever the instantaneouspressure falls below the vapor pressure.This effect is sometimes called pseudo-cavi-tation, to distinguish it from the effect inpure degassed liquids, where an actual rup-ture of the medium occurs (at much highersound pressures). Collapse of such cavitiesproduces very large impulsive pressuresthat may cause considerable mechanicaldamage to neighboring solid surfaces.

CAVITATION DAMAGE — Wearing awayof solid material through the formation andcollapse of cavities in an adjacent” liquid.

CEILING, n.— Tbe height atwve the earth’asurfsce of the lowest layer of the cloudsor obscuring phenomena that is reportedse broken, overcast, or obscuration, andnot classified se thin or pafilal. (ND)

CEILING LIGHT — A type of cloud-heightindicator which uses a searchlight to pro-jed vefi~cslly a narrow beam of light ontoa cloud base. The height of the cloud base

27


MIL-STO-116S25 MARCH 1968

is determined by using a clinorneter, lo-cated at a known distance from the ceilinglight, to measure the angle included by theilluminated spot on the cloud, the observer,and the ceiling light. (AMS)

CEILOMETER, n.— An automatic, record-ing, cloud-height indicator. (AMS)”

CELSIUS TEMPERATURE SCALE-Sameas CENTIGRADE TEMPERATURESCALE, by recent convention. The NinthGeneral Conference on Weights and Mess-ures ( 1948) replaced the designation “de-gree centigrade” by “degree Celsius.”(Originally, Celsius took the boiling pointas O degrees and the ice point as 100 de-grees. ) (AMS)

CENTIGRADE TEMPERATURE SCALE— A temperature scale with the ice pointat O degrees and the boiling point of waterat 100 degrees. Conversion to the Fahren-heit temperature scale is according to theformula

‘C =+(” F—32). (AMS)

CENTRIFUGE, n.— A machine used in en-vironmental testing to subject material tosteady state rotational acceleration abouta fixed axis.

CHALK, n.— A very soft, white to lightgray, ,fine-grain@ variety of limestone

‘ composed largely of the calcareous shellsof small marine organisms.

CHALKING, n.— A surface coating failurecommon to paints, varnishes, lacquers, andrelated formulations, particularly when ex-posed to exterior environmental weather-ing. It is characterized by the formation ofa chalklike powder on the surface attrib-uted to film deterioration by the blue andultra-violet wavelengths of the sun’s radi-ant energy. In white exterior paints, c’halk-ing may be desirable to impart se]f-cleaningproperties. In colored exterior paints onbuildings or equipment, chalking impartsa faded-out ~ppearance and dullness fromaccumulation of surface chalk.

CHAMBER, n. — An enclosed environmental

laboratory facility used for duplicating,accelerating, or simulating one or morenatural environmental phenomena, singlyor in various combinations.

CHAMBER, ACCELERATED WEATHER-ING — A type of laboratory facility de-signed to accelerate the effects of naturalaging. Some are oriented to a single mate-rial, others to several materials. Usual] ycontains controls for light and heat, and,in some cases, for humidity.

CHAMBER, ALTITUDE — A combined-function test chamber furnishing controlledconditions of temperature and low absolutepressure (altitude). Temperature require-menta vary from —100” F., or lower, to1000” F. Altitude requirements vary up toand above 500,000 feet (3.385 x 10-s psior 1.8 mi]limicrons).

CHAMBER, ARID — An environmental testfacility simulating high temperature, lowhumidity, and solar radiation heat and lightas found in arid areas of the earth.

CHAMBER, CLEAN — An enclosed area inwhich airborne contamination (particulaterhatter) and, if necessary, temperature, hu-midity, and air pressure are controlled to afar higher degree than in conventional air-conditioned areas. Commonly referred toas CLEAN ROOM. (Federal Standard No.209)

CHAMBER, CLIMATIC — See CHAMRER,HUMIDITY.

CHAMBER, FOG —A confined space in whichsupersaturation of air or other gas is pro-duced by reduction of pressure, cooling. orother means, producing an artificial fog.

CHAMBER, HIGH TEMPERATURE — Anenclosed facility for producing thermostati-cally controlled high temperatures (usuallyby resistance heaters) used to determinethe effect of high temperatures on a “testitem.

CHAMBER, HUMIDITY—A laboratory fa.cility constructed with a conditioning de-vice used to maintain a specifie~i h“midi:yat a speciiied tenlpertiure. -The control

2s


e range may vary with specific supplications,,and construction purposes. Normal con-struction range: Humidity, frost point(F. P.) –15° C. to dewpoint 85° C.; drybulb temperature, 15” C. to 93” C.; baro-metric pr~ure, 24.9(I inches of mercuryto 30.27 inches of mercury. This chamberis a specialized facility with difficult con-trol requirementa.

CHAMBER, LOW TEMPERATURE—Anenclosed, thermally-insulated facility withequipment and controls to produce an in.ternal temperature below the ambient tem-perature. Refrigeration can be accom-plished by mechanical single stage systems,mechanical two-stage compound systems,multi-stage cascade systems, dry ice, orliquid carbon dioxide. Low temperaturescan beattaincd down to —150” F., depend-ingon the system and the refrigerant used.The chambers maintain internal tempera-ture conditions by convection and/or radi..ation.

CHAMBER, REVERBERANT—A type of

.*

acoustical testing facility in which a spwi-men is subjected to simultaneous impinge-ment of acoustical energy from many di-rections. It is characterized by highly re-flective walls and may have non-parallelopposing walls or multiple energy sources.

CHAMBER, SALT SPRAY — An environ-mentaI test chamber for accelerated corro-sion testing. A salt solution is atomized bythe use of suitable nozzles in conjunctionwith a compressed sir supply. The cham-ber is also equipped for heating the system.

CHAMBER, SOLAR RADIATION — An en-closed facility provided with a means forproducing a simulated solar radiation en-vironment including ther,mostaticslly con-trolled temperature. There are two types ofsolar simulation: (1) terrestrial ; and (2)space.

CHAMBER, TEMPERATURE — An en.closed, thermally-insulated space withequipment and controls to produce a cham-ber temperature differing from ambient.


CHANNEL, n.— 1. A band of radio frequenc-ies wide enough to SIIOW transmiaaionwithout interference from transmission onadjacent bands. 2. A natural or artificialwaterway which either periodically or con-tinuously contains moving water, or whichforms a connecting link between two bodiesof water. (NOO) 3. The part of a body ofwater deep enough to be used for navigationthrough an ares otherwise too shallow fornavigation. (NOO ) 5. Tbe de+?pestportionof a stream, bay, or strait through whichthe main volume or current of water flows.(NOO) 6. A lead in pack ice. (NOO) 7.The complete route for transmission ofdata, from source to recorder.

CHANNEL, TELEMETER — The completeroute for transmission of a telemeteredfunction, including pick-up, commutator,modulator, transmitter, receiver, demodu-lator, decoder, and recorder.

CHAPARRAL, n. — Low dense scrub vege-tation, principally drought-resistant shrubsand. bushes, which is characteristic of re-gions having a subtropical summer-dry(Mediterranean) climste; usually appliedto that part of California which enjoysthis climate. It corresponds to the maquis ofthe Md]termnean area in Europe. In someplaces it is almost impenetrable, consistingof thickets of stiff or thorny shrubs ordwarf trees,

CHATTER CALIBRATION — A method ofaccelerometer calibration in which the ac-celerometer and a gravity-constrained“chatter-ball” are mounted on a verticalvibrstion table, the one G downward accel-eration being indicated by separation of theball. (SVH)

CHECKING, n.— A surface coating failureof painta, varnishes, lacquers, and relatedformulations. It is characterized by theformation of small surface breaks in thecoating which do not penetrate to the un-derlying surface. If the underlying surfaceis visible, crackling is the term used to de-note these breaks.

29


. . ------ . . .NIIL+IU-I lea25 MARCH1968 ‘

CHEMICAL CONVERSION COATINGS —Thhr inorganic films produced by chemicalor electrochemical reactions with the sur.face of the base metal. They differ frompainta and most metallic coatings in thatthey are an inte~al part of the base metal.Conversion coatings can be divided intophosphate, ,chromate, chemical oxide, andanodic coatings.

CHEMICAL STABILITY — The ability of amaterial to resist decomposition caused bysuch factors as heat, light, and chemicalattack.

CHERNOZEM, n. — Pedolog~. A zonal greatsoil group consisting of soils with a thick,nearly black or black, organic matter-rich“A” horizon high in exchangeable calcium,underlain by a lighter colored transitionalhorizon above a zone of calcium carbonateaccumulation; occurs in a cool subhumidclimate under a vegetation of tall and mid-grass prairie. (SSS) ,.

CHINOOK — See FOEHN.

CHLORINITY, n.— A measure of the chlor-ide content, by mass, of sea water (gramsper kilogram of sea water, or. per mine).Originally chlorinity waa defined as theweight of chlorine in grams per kilog-ramof sea water after the bromides and iodideshad been replaced by chlorides. To makethe definition independent of atomicweights, chlorinity is now defined as0.3285233 times the weight of silver equiva-lent to all the halides. (AMS) ●

CHOCKING, n.— The condition which pre-vails in compressible fluid flow when theuPWr limit of mass flow is reached, or whenMach 1 is reached in a duct.

CHOPPY, adj. — L Of the sea, having short,abrupt, breaking waves dashing againsteach other; chopping. (ND) 2. Of thewind, variable, unstable, changeable; chop-ping. (ND)

CINDER-CONE — A conical elevationformed by the accumulation of volcanic aahor cinder-like material around a vent;called also ash cone. (GS)

CINDERS, n.— Same as VOLCANIC CIN-DERS.

CINDER SURFACE — The surface formedby small particles of vesicular lava ejectedfrom a volcano. Often many feet deeparound the vent and gradually thinning outuntil the layer is no thicker than the in-dividual cinder at distances of a few miles.

CIRQUE, n.— A deep, steep-walled recess ina mountain, caused by glacial erosion.

CLASTICS, n.— Deposits which are madeup of fragments of pre-existing rocks or ofthe solid products formed during the chem-ical weathering of such older rocks. Famil-iar examples of sediments belonging to thisgroup are GRAVEL, SAND, MUD, andCLAY, and their consolidated equivalents,CONGLOMERATE, SANDSTONE, andSHALE. (S&V) ●

CLAY, n.— 1. Soil mechanics. In the UnifiedSoil Classification System, defined as a soilthat contains more than 50 percent particleswith diameters less than 0.047 mm and hasa plasticity in relation to its LIQUID LIM-IT. Types are identified as CL (lean clay), .0

CH (heavy clay), OL (organic clay of lowplasticity), and OH (organic clay of highplasticity. (Mil Std 619) 2. A soil separateconsisting of particles less than 0.002 mmin equivalent diameter. (SSS ) 3. Pedology.The U.S. Department of Agriculture tex-tural class name for soil that contains 40percent or more of clay, less than 45 percentof sand, and less than 40 percent of silt.(YA)

CLAY LOAM — Soil that contains 20 to 45percent sand and 27 to 40 percent Clay.(YA)

CLAYPAN, n. — A dense, compact layer inthe subsoil having a much higher clay con-tent than the overlying material, fromwhich it is separated by a sharply definedboundary; formed by downward movementof clay or by synthesis of clay in place dur-ing soil formation. Claypans are usuallyhard when dry, and plastic and sticky whenwet. Also, they usually impede the move-

30


ment of water and air, and the growth ofplant roots. (SSS)

CLEAN ROOM — See CHAMBER, CLEAN

CLEAR AIR TURBULENCE — Turbulenceencountered by aircraft when flying throughair space devoid of clouds. The main causesare wind shears and small-scale rising cur-rents of clear air (THERMALS). (AMS) *

CLIFF, n.— A high steep face of rock. Acliff of considerable length is often calledan ESCARPMENT or SCARP. Cliffs areusually produced by erosion, less commonlyby faulting. (S&V)”

CLIMATE, n.— The long-term manifesta-tions of WEATHER, however they may beexpressed, More rigorously, the climate ofa specified area is represented by the sta-tistical collective of its weather conditionsduring a specified interval of time (usuallyseveral decades). (AMS) ●

CLIMATIC SNOW LINE — The altitudeabove which snow accumulates in excess ofwastage. Also called regio+ud snow line, andfirn tine when referable to a glider or icecap. The climatic snow line specifically ap-plies to flat surfaces fully exposed to sunand wind; however, moat glaciologists con-sider the precise application as theoretical,rarely observable in nature. (ADT).

CLIMATIC TEST — A generic term describ-ing any test designed to evaluate the ef.fects of climatic conditions on the equip-ment undergoing the test, Climatic testsusually include sunshine, rain, hail, snow,sleet, wind, humidity, sand, dust, tempera-ture, fungus, salt spray, etc.

CLIMATIZATION, n. —All measures taken toprovide for the satisfactory operation, pack.aging, transportation, and storage of equip-ment under specified climatic conditions.

CLIMATOLOGY, n.— The scientific study ofclimate. In addition to the presentation ofclimatic data (climatography), it includesthe analysia of the causes of differences ofclimate (physical climatology), and the ap-


plication of climatic data to the solution ofspecific desigm or operational problems (ap-plied ctimutolog~). Climatology maybe fur-ther subdivided according to purpose orpoint of view: amicultural climatology, air-maas climatology, aviation climatology, bio-climatology, dynamic climatology, medicalclimatology, macroclimatology, mesoclima-tology, microclimatology, paleoclimatcdogy,synoptic climatology, upper-air climatology,descriptive climatology, and others. (AMS) *

CLINOMETER, n.— Any of various inatru-menta for measuring angles of slope, in-clination, elevation, or the like, such as theangle between the horizontal and the line ofsight to the spot of light thrown by a ceil-ing projector, or between the horizontal anda ship’s axis. (NASA)

CLO, .n. — The unit of measurement used inevaluating the insulative quality of cloth-ing. A CIOis the amount of insulation neededto assure a mean skh tem~rature of 92” Fin an ambient temperature of 70” F,, withrelative humidity not over 50 percent andair movement of 20 feet per minute or less,and with an assumed metabolic rate of 50Kcaloriea per square meter per hour. Al-lowing 76 percent heat loss through cloth-ing, a C1Obas been defined as the amount ofinsulation required to permit the escape ofone Kcalorie per square meter per hour witha temperature gradient of ,18° C betweenthe two surfacea. (AMS) *

CLOD, n.— A compact, coherent mass of soilranging in size from 5 or 10 mm to x muchas 8 or 10 inches; preducad artificially, us-ually by the activity of man by plowing,digging, etc., especially when these o~ra-tions are performed on soils that are eithertoo wet or too dry for normal tillage oper-ations. (SSS)

CLOSE ICE — Ice that covers from 8/10ths(80 percent) to 10/10ths (100 percent) ofthe sea surface. The floes are not frozen to-gether if the cover is 10/10ths ( 100 per-cent). (IG) *

CLOUD, n.— 1. A hydrometer consisting of

31



a visible aggregate of minute water and/orice particles in the atmosphere above theearth’s surface. Cloud differs from FOGonly in that the latter is, by definition, incontact with the earth’s surface. (AMS) *2. Any collection of particulate matter inthe atmosphere dense enough to be percepti-ble to the eye, as a dust cloud or a smokecloud. (AMS)

CLOUD BANK — Generally, a fairly well de-fined mass of tloud observed at a distance;it covers an appreciable portion of the hori-zon sky, but does not extend overhead.

~ (AMS)

CLOUDBURST, n.— A sudden and extreme-ly heavy downpour of rain. (ND)

CLOUD-CHAMBER EFFECT — The con-densation of moisture in the air due to cool-ing which is caused by the rapid expansionof air (in the negative phase) after an. ex-plosion (analogoua to the effect used bynuclear physicists in the Wilson cloud cham-ber).

CLOUD COLUMN — The visible column ofsmoke which may extend to the tropopausesubsequent to an air burst of an atomicweapon, and the corresponding smoke col-umn subsequent to any other type of burst.

CLOUD PHYSICS — The body of knowledgeconcerned with physical properties of clo~ldsin the atmosphere and the processes occur-ring therein. Cloud physics, broadly con-sidered, embraces not only the study of con-densation and precipitation processes inclouds, but also radiative transfer, opticalphenomena, electrical phenomena, and aw,ide variety of hydrodynamic and thermo-dynamic processes peculiar to naturalclouds. (AMS) “

CLUTTER, n.- Atmospheric noise, extrane-ous signals, etc. which tend to obscure thereception of a desired signal in a radio re-ceiver, radar scope, etc. As compared within terfcmvwej clutter refers more particu-larly to unwanted reflections on a radarPPI, such ae ground return, but the terms

are often used interchangeable y. (ND)

COALESCENCE, n.— In cloud physics, themerging of two water drops into a singlelarger drop. (AMS)

COATING, ANODIZED — An oxide coating,produced by electrolytic means, for alumi-num, magnesium, and their alloys. Gener-ally, anodized coatings are hard, abrasionresistant, and offer excellent resistance tocorrosion. See ANODIZING.

COBBLE (COBBLESTONE), n.— Roundedor partially rounded rock or mineral frag-ment between 3 and 10 inches in diameter.(sss):,

COEFFICIENT OF EXPANSION—The rel-ative increase of the volume of a system (orsubstance ) with increasing temperature inan isobaric process. (A?vIS) *

COHESION, n.— .Soit Meckmtics. The capac-ity of sticking or adhering together. In ef-fect, the cohesion of soil is that part of itsshear strength which does not depend uponinter-particle friction. True cohesion is at-tributed to the shexring strength of thecement or the absorbed water films that sep-arate the individual grains at their areas ofcontact. Apparent cohesion of moist soils isdue to surface tension in capillary openingsand disappears completely on immersion.“(s&v) ‘

COL, n.— A short ridge connecting two high-er elevations; a narrow pass joining twovalleys; a pass between adjacent peaks in amountain chain. (GS)

COLD DRY — In military climatology, aweather condition in which cold, or verycold temperatures are unaccompanied bywet precipitation or wetness on the ground,except that dry snow may be falling or drysnow or ice may be underfoot. (.%DT) *

COLD SOAK — The effect of exposing equip-ment to low temperatures for an extendedperiod of time. Cold soak of engines some-times necessitates preheating before theiruse, as lubricants have thickened, metal has

32


‘“’* become brittle, and tolerances have dimin-ished. (ADT)*

COLD WET — 1. Militar?j climctol. A wea-ther condition in which cool, cold, or verycold temperatures are accompanied by rain,fog, or wet snow in the air and by the pres-ence of water, wind, slush, or wet snow onthe ground. (ADT) * 2. PhysioL An envi.ronmentsl condition in which clothing is es-sential to prevent the loss of body heat fromexceeding the production of metabolic heatwhen the problem is complicated by thepresence of moisture in the air or underfootwhich wets clothing, especially footgear.(ADT) “

COLLOID, SOIL — Organic or inorganicmatter of very small particle size and verylarge surface area per unit of mass. Inor-ganic colloidal matter consists almost en-tirely of CLAY minerals of various kinds.Not all clay particles are colloids; usuallyonly particles smaller than ,00024 mm areso designated. (NAS)

,“‘a COLLUVIUM, n.— A deposit of rock frag-ments and soil material accumulated at thebase of steep slopes as a result of gravita-tional action. (SSS ) *

COMPACTION, n.— 1. Gcotog~. The changing of loose sediments to hard, firm rocks.2. ,Soil Mechanics. Any process by whichsoil grains are rearranged to decrease voidspace and bring them into closer contactwith one another, thereby increasing thetieight of solid material per cubic foot. Non-cohesive soils are most effectively compactedby vibration; moderately cohesive Soils arecompacted by sheepsfoot or other types ofrollers. (S&V)”

COMPATIBILITY, n.— The particular qual-ity or characteristic of a component, anitem of equipment, or a system which per-mits it to function in harmony with otherequipment, environments, or systems witha minimum amount of adapters, extensions,transformers, or other equalizer unita.

o COMPLIANCE, n. — The reciprocal of

33

MiL-STD-l 165!25 MARCH 1968

STIFFNESS. (SVH)

CONCRETION, n.— A local concentration ofa chemical compound, such as calcium car-bonate or iron oxide, in the form of a grainor nodule of },arying size, shape, hardness,and color. (SSS)

CONDENSATION, n.—The physical processby which a vapor becomes a liquid or solid;the opposite of evaporation. In meteorologi-cal usage, this term is applied only to thetransformation from vapor to liquid; anyprocess in which a solid forms directly fromits vapor is termed sublimation, as is thereverse process. In meteorology, condensa-tion is considered almost exclusively withreference to water vapor which changes todew, fog, or cloud. It is indispensable toavoid confusing condensation with precipi-tation,, for the former is by no means equiv-alent to the latter, though it must alwaysprecede the latter. (AMS$)*

CONDUCTION, n.— The transfer of energywithin and through a conductor by meansof internal particle or molecular activity,and without any net external motion. Con-duction is to be distinguished from convec:tion (of heat) and radiation (or all electro-magnetic energy ). Heat ia conducted by mc-Iecular motion within a few centimeters ofthe heat source (e.g., the earth’s surface).The distribution of heat away from thatsource is accomplished by convection and(in analogy to molecular conduction) byeddy heat conduction. (AMS ) *

CONE INDEX — Soil Mechanics. An indexof the shearing resistance of soil obtainedwith the CONE PENETROMETER; anumber representing resistance to penetra-tion into the soil of a 30-degree cone witha one-half inch base (actually, load inpounds on cone baae area in square inches).

CONE OF SILENCE — An inverted cone-shaped space directly over the aerial towersof some forms of radio beacons in whichsignals are unheard or greatly reduced involume. (JD)


MlL-STD-l 16525 .MARCH 1960

CONE PENETROMETER— An instrument CONTAMINATION, n. — The deposit or ab-used to measure the ability of a soil to snp- sorption of radioactive material, biological,porttraffic movements. (AD) or chemical agents on and by structures,

CONGELIFRACTION, n.— See FROST AC-areas, personnel, or objects. (JD).

TION CONTINENTAL AIR — A type of air whose

CONGELITURBATION, n. — See FROSTACTION

CONGLOMERATE, n. —Hard rock formedby the natural cementing together ofrounded pebbles (gravel ). A similar rockformed of larger fragments may be calleda cobble conglomerate or a boulder con-glomerate, as the case may be.

CONIFER, n.— A tree or.shrub belonging tothe order Cortiferales. Most conifers areneedleleaf plants, but some have scalelikeleaves ranging from small, as in many juni-

: pers and cedars, to more than an inch wide,I as in the monkeypuzzle tree Most species of

conifers are evergreen, but the larches, andsome others, are deciduous,

CONSOLIDATED ICE — Ice that covers 10-10ths (100 percent) of the sea surface; thefloes are frozen together. ( IG)

CONSOLIDATION, n.— 1. GcologJ. Any orall of the processes whereby loose, soft, orliquid earth materials become firm and co-herent. Any action that increases the solid-ity, firmness, and hardness is important inconsolidation. Cemen~ation is probably themost important factor, followed by mechan-ical rearrangement of constituents throughpressure, crystallization, mrd loss of water.The term also describes the change of lavaor magma to firm rock. 2. Soil Mechanics,The adjustment of a saturated soil in re-sponse to increased load, involving thesqueezing of water from the pores and de-crease in void ratio. The rate of consolida-tion depends upon the rate at which the porewater escapes, and hence upon the perme-ability of the soil. (S&V) *

CONTACT HAZARD — A hazard resultingfrom direct bodily contact with forei~ sub.stances (nuclear, chemical, biological), orfrom prolonged contact with contaminants.

characteristics are de~eloped over a largeland area and which, therefore, has thebasic continental characteristic of relative-ly low moisture content. (AMS)

CONTINENTAL CLIMATE — The climatethat is characteristic of the interior of aland mass of continental size. It is markedby large annual, daily, and day-to-dayranges of temperature, low relative humid-ity, and (generally) by a moderate or smalland irregular rainfall. The annual extremesof temperature occur soon after the SOl-stices. (AMS) *

CONTINENTAL SHELF (or CONTINENTALPLATFORM) – A zone adjacent to acontinent or around an island, and extend-ing from the low water Line to the depth atwhich there is usually a marked increase ofslope to greater depth. (NOO)

CONTINENTAL SLOPE — A declivity sea- ●ward from a CONTINENTAL SHELFedge into greater depth. (NOO)

CONVECTION, n.— 1. Mass motions withina fluid resulting in transport and mixing ofthe properties of that fluid. Convection,along with conduction and radiation, is aprincipal means of energy transfer.(AMS) * 2. Meteorol. Atmospheric motionsthat are predominantly vertical, resultingin vertical transport and mixing of atmo-spheric properties; distinguished from ad-vection. ( AlIS)” 3. ..lhrzosphmic Electric-ity. A process of vertical charge transferby transport of air containing a net spacecharge, or by motion of other media (e.g.rnin) carrying net charge. Eddy diffusionof air containing a net charge gradient mayalso yield a convection current. (AXIS)

COOLING POWER — In the study o! humanbioclimatolo~W, one of several parametersde~,ised to measure the air’s cooling effect

34


I● upon a human body. Essentially, cooling

power is determined by the amount of ap-plied heat required by a device to maintainit at a constant temperature (usually34”C) ; the entire system should be madeto correspond, as closely as possible, to theexternal heat exchange mechanism of thehuman body.

COQUINA, n.— Soft porous limestone tom.posed of broken shells, with or without cor-als and other organic debris.

CORAL, n.— The hard calcareous skeleton ofvarious small sea animals (polyps), or thestony solidified mass of a number of suchskeletons. In warm waters colonial coralforms extensive reefs of limestone. In codor cold water coral usually appears in thefO1711Of isolated solitary individuals. Occa.sionaly, large reefs formed in cold watersby calcareous ALGAE have been referredto as coral. (NOO)”

CORAL REEF — A ridge or mass of limestone built up of detrital material deposited

9

around a framework of the skeletal remainsof mollusks, colonial coral, and massivecalcareous algae. Coral may constitute leesthan half of the reef material. (NOO)

CORDUROY ROAD — A form of support orroadway over soggy or soft terrain, usu-ally made from loge laid crosswise to thedirection of travel.

CORIOLIS EFFECT — 1. The apparent de-flection of an object (e.g. a missile, air-plane, or mass of air) in motion above thesurface of the earth relative to positions onthe surface, which is rotating beneath themoving object; the deflection is to the rightin the northern hemisphere and to the leftin the southern hemisphere. 2. A phenome-non observed in rotati~g systems; ~ee COR-IOLIS FORCE.

CORIOLIS FORCE — An apparent force ona body moving within a rotating system. Itis always at right angles to the direction ofthe body’s motion and proportional to the


and to the bedy’s momentum (mv ) ; themagnitude is 2 .,mv, See CORIOLIS EF-FECT.

CORONA, n. — 1. A set of one or more pris-matically colored rings of small railii, con-centrically surrounding the disk of the sun,moon, or other luminary when veiled by athin cloud. The corona is due to diffractionby numerous water drops. It can be distin-.~ished from the relatively common halo of22” by the much smaller angular diameterof the corona, which is often only a few de-grees, and by its color sequence, which isfrom blue inside to red outside, the reveracof that in the 22” halo. (AMS) * 2. Thepearly outer envelope of the sun. It is ob-served at solar eclipse or with the corona-graph. (AMS) *

CORONA DISCHARGE — The flow of elec.trical energy from a conductor at high po-tential to the surrounding air. If the con-ductor has an insulating covering, the coro-na discharge will take place at the outersurface of the insulation, and if there arevoids or air spaces between the conductorand ita insulation, corona discharge willprobably take place at these pointa. The dis-charge is accompanied by a faint glow anda “frying” noise and has the ability to con-vert the oxygen of the air to ozone.

CORONA RESISTANCE — The ability of amaterial to withstand the effects of coronadischarge.

CORRASION, n.— Mechanical erosion per-formed by moving agents such as wear byglacial ice, wind, running water, etc., butgenerally restricted to basal rather thanlateral excavation. (NOO) *

CORROSION, n.— The gradual deteriorationof material by chemical processes, such asoxidation or attack by acids; if caused byatmospheric effects, a form of WEATHER-ING. Of great significance is the corrosiondue to the combined effects of atmospherictemperature, humidity, and suspended im-purities; for example, the rusting of iron.

angular velocity (w) of the rotating system

‘o

~AMS)*

35



CORROSION, CATHODIC — Corrosion re-sulting from a cathodic condition of a struc-ture, usually caused by the reaction of alka-line products of electrolysis with an arnpho-teric metal. (ECS).

CORROSION, COEFFICIENT OF — The re-ciprod of anode corrosion ef?lciency. Aterm used in applied cathcdic protection.(ECS)

CORROSION, CREVICE — Corrosion of ametal “at an area where contact ia made withanother material, usually non-metallic. Alesknown as contact corrosion.

CORROSION, DESTRUCTIVE — Any typeof corrosion which so weakens the basicmetal that it can no longer function or suppat the functions for which it was origi-nally intended.

CORROSION, ELECTROCHEMICAL — Lo-calized corrosion that results from exposureof an assembly of dissimilar metals in con-tact or coupled with one another; or of ametal containing macroscopic or microscop-ic areas disimilar in composition or struc-ture. The dissimilar elementi form ahort-circuited electrodes; the corrosive mediumis the electrolyte and an electric current iainduced, which results in the di.wolution ofthe ekctrode that has the more anodic solu-tion potential, while the other is unattachd.The same condition may result from lwaldifferences within the corroding medium.

CORROSION EMBRITTLEMENT — Thesevere loss of ductility of a meta! or alloyresulting from corrosion attack, usually in-tergranular and often not visually apparent.

CORROSION FATIGUE — Reduction of fa-tigue durability by a corrosive environment.(ECS)

CORROSION FATIGUE LIMIT — The max-imum repeated stress endured by a metalwithout failure in a stated number of stressapplications under defined conditions of cor-rosion and stressing. (ECS )

CORROSION, FRETTING — Corrosion at

the interface between two contacting sur-faces accelerated by reIative vibration be-tween them of amplitude high enough to ●produce slip. ( ECS)

CORROSION, GALVANIC (COUpLE AC-TION) — Corrosion associated with thecurrent of a galvanic cell made up of dis-similar electrodes. (ECS)

CORROSION, INTERGRANULAR (IN-TERCRYSTALLINE CORROSION) — Atype of electrochemical corrosion that pro-gresses preferentially along the grainboundaries of an alloy, usually because thegrain boundary regions contain materialanodic to the central regions of the grains.

CORROSION PREVENTION — The protec-tion given metallic items by covering sur-faces subject to corrosion to prevent con-tact with water, moisture vapar, acids, andother contaminating substances or storagein a dehumidified air, It includes carefulcleaning of all or part of the items, the ap-plication of a barrier of oil, grease, or mois-ture vapx proof paper to exclude air andmoisture, and the covering of the barrier toprovide for its protection. (AD) o

CORROSION PREVENTIVE — Any agentsuch as oil, plastic, paint, wrap or other sur-face treatment of metals whose primaryfupction is to prevent corrosion. May ex-clude atmosphere by meana of a continuousfilm, or may direct corrosion to another ele-ment (cathodic protection ). (AD)

CORROSION PREVENTIVE COMPOUND— A compound applied to metal surfaces toprevent rust or corrosion. The term is usu-ally applied to compound which can be re-moved by water or solvent cleaners in orderto distinguish them from paint films. (AD)

CORROSION, STRAY CURRENT — Corro-sion caused by current through paths otherthan the intended circuit or by an extrane-ous current in the earth. (ECS)

CORROSION, STRESS — Corrosion of ametal accelerated by stress.

36


CORROSION TEST — A test designed to de-termine the adequacy of a part for with-standing corrosion under specified condi-tions for a known length of time. Varioustest procedures are spelled out in applicableliterature of the Institute of EnvironmentalScience, ASTM, American Electroplater’sSodety (AES), National Association ofCorrosion Engineers, and in Governmentspecifications.

CORROSION, UNDERFILM — Corrosionthat occurs under lacquers and similar or-ganic films in the form of randomly dis-tributed hairlines (most common ) or spots.(ECS)

COSMIC RAYS (or COSMIC RADIATION)— Extremely high-energy charged pa~lcleearriving in the vicinity of earth from be-yond the solar system (galactic cosmicrays) or from the sun (solar cosmic rays).They consist mostly of protens (hydrogennuclei) and alpha particles (helium nuclei).Secondary cosmic rays are produced by theinteraction of the incoming (primary) cos-mic rays with the atmosphere.

COSMIC RAYS, HARD COMPONENT —That portion of cosmic radiation which pen-etrate a moderate thickness of an absorber(usually 10 cm of lead). The bard compo-nent, except near the top of the atmosphere,consists of mesons to a predominant degreebut includes some fast protons and elec-trons.

COSMIC RAY SHOWER — The simultane-ous appearance of several or many lightionizing particles with or without accom-panying photons, the particles being di-rected predominantly downward and hav-ing a common ultimate origin in an eventcaused by a single cosmic ray. Showers re-veal themselves by the simultaneous actua-tion of separated counters and (sometimess~tacularly) in cloud chambers. They canhe roughly classified according to theirproperties as narrow showers, exclusive (orAuger) showers, penetrating showers, andcascade showers.


COSMIC RAYS, SOFT COMPONENT —That portion of cosmic radiation which isabsorbed in a moderate thickness of an ab-sorber (usually 10 cm of lead). It consistsmainly of electrons, positrons, and photons,but contains some slow mesons, slow pro-tons, and other heavy particles often pres-ent in cosmic radiation.

COULEE, n. -1. A steep-walled, trench-likevalley of considerable size through whichwater flows intermittently. See ARROYO,BARRANCA, DRY WASH, and WADI.2. More specifically, any of a number ofsteep-walled, trench-like valleys cut into theColumbia Plateau lava sheets in the stateof Washington, and formerly occupied byglacial meltwater rivers. (S&V) ●

COVER, n.— Shelter or protection, eithernatural or artificial. (JD) (Other meaningsin JD are not applicable to environment).

COVER, FOREST — All trees and otherwoody plants in a forest. (SAF)

CRACK, n. — L Fissure or crevice in a rockor ice formation. (ADT) 2. A water-reveal-ing narrow break in sea ice that may be ex-panded to lead size by boring. It ia usuallypossible to jump across a crack. (IG)” 3. Afissure or crevice type of failure in materi-als caused by operational or environmentaltests.

CRACKING, n.— Deterioration of a coatingcharacterized by breaks that extend throughto the underlying surface. (ECS)”

CRASH SAFETY — A type of shock teat in-tended to determine the mechanical integri-ty of equipment hardware under simulatedaircraft crash landing loads.

CRATER, n.— 1, The bowl-shaped depressionaround the vent of a volcano or a geyser.2. A hole formed by the impact of a mete-orite, the detonation of a mine, or the like.(GS)

CRAZING, n.— A network of checks orcracks caused by extremes of temperature,appearing on a surface. It may also be

37



caused in plastics by certain cleaning fluids,age, and ultraviolet exposure.

CREEP, n.— 1. The flow or plastic deforma-tion of materiala held for long periods oftime at stresses lower than the rupturestress. 2. Geol. A slow downsiope movementof soil or rock debris, usually imperceptibleexcept by prolonged observation, tree tilt,or ragged scars in the ground cover. Creepis caused by the combined actions of grav-ity, ground water flow, freezing and thaw-ing or swelling and shrinking of the, soil.(ADT)

CREST, n.— 1. The summit land of any emi-nence; the highest natural projection thatcrowns a hill or mountain, from which thesurface dips downward in opposite direc-tions. (GS) 2. The highest part of a ‘waveor swell. (ND) ● 3. The more or less nar-row, irregular longitudinal top of an ele-vation of the sea bottom, such as a ridge orseamount. (ND) 4. A terrain feature ofsuch altitude that it restricts fire or obser-vation in the area beyond resulting in deadspace, or limiting tbe minimum elevationor both. (AD)

CREVASSE, n.— 1. A fissure or rift in aglacier or other land ice mass, caue’ed bymovement of the ice. (ADT) 2. A break ina levee or other stream embankment. (GS)”

CRITICAL ENERGY — The minimum orcritical quantity of heat energy per unitarea which is necessary to produce a de-fined change in a given material, e.g., char-ring, melting, burning; expressed in Cal-ories per square centimeter.

CRITICAL POINT — A point where there isa change in direction or change in slope ina ridge or stream. (JD )

CRITICAL TEMPERATURE — 1. The tem-perature at which magnetic materials losetheir magnetic properties; about 800° C foriron and steel, 2. The temperature at whichsome change occurs in a metal or alloy dur-ing heating or cooling. 3. The temperatureabove which a given gas cannot be liquefied.

CROCKING, n.— 1. The loose black particlescollected from combustion as on pots andkettles, or in a chimney; soot. 2. Coloringmatter which rubs off from cloth, dyedleather, etc.

CROSS-COUNTRY TERRAIN —Terrain notspecifically improved for vehicular traffic.(WES)

CROSS TALK — An interfering signal re-ceiv~ from a transmitter other than that ,to which a receiver is tuned. Cross talk canwcur between adjacent channels of multi-channel instrumentation. (ND) *

CROSSWIND — That wind vector componentwhich is perpendicular to the course of anexposed moving object. A wind blowing ina direction approximately 90° from a ship’sheading is called a beam wind. In commonusage these two expressions are often usedsynonymously, crosswind being favored byaviators and beam wind by mariners.(NOO)”

CROWN, n. — The upper part of a tree, in-cluding the branches with their foliage.

CRUMB, n.— A soft, porous, more or lessrounded unit of soil structure from 1 to 5mm in diameter, (SSS) ●

CRUST, n.— 1. The surface layer of ice orhard snow overlying a deposit of softersnow. A crust is formed by the melting andrefreezing of the surficid layer, sometimesaugmented by wind compaction. (ADT)2. A surface layer on soils, ranging in thick-ness from a few millimeters to perhaps asmuch as an inch, that is much more com-pact, hard, and britt!e, when dry, than thematerial immediately beneath it. (SSS )

CRYOGENICS, n. — 1. The study of physicalphenomena at temperatures below approxi-mately —150° C. (—238° F.). 2. More gen-erally, a term referring to methods of pro-ducing very low temperatures.

CRYOLOGY, n.— 1. The study of ice andsnow, (ADT) 2. The study of sea ice.(ADT) 3. In the United States, the studyof refrigeration. ( .ADT). 4. In Europe a

38


Q synonym for GLACIOLOGY.

Note: The Lcrm cryology has become almostmeaningless unless it is defined in context.

CX2YOPEDOLOGY, n. — The study of inten-sive frost action and PERMAFROST, theircauses and occurrences, and the engineer-ing devices and practices which overcomedifficulties brought about by them. (ADT)

CRYSTALLINE ROCK — Rock consisting ofclosely fitted mineral crystals rather thanof cemented grains or volcanic glass; e.g.,most metamorphic and igneous rocks.

CUBIC FEET PER SECOND — A unit ofmeasure expressing rate of discharge. Onecubic fad per second is equal to the dis-charge of a stream of rectangular cross sec-tion, 1 foot wide and 1 foot deep with aliquid flowing at an average velocity of 1foot per second. Abbreviated cfg.

CUBIC FEET PER SECOND PER DAY(Abbreviated cfs-day) — The volume ofwater represented by a flow of 1 cubic footper second for 24 hours. It equals 86,400cubic feet, 1.983471 acre-feet, or 646,317gallona. (MH)

CUBIC FEET PER SECOND PER SQUAREMILE (Abbreviated cfsm) — The averagenumber of cubic feet of water per secondflowing from each square mile of areadrained by a stream, assuming that the run-off is distributed uniformly in time andarea. (MH)

CUESTA — An “asymmetric ridge with asteep slope or cliff on one side and a gentlysloping plain, the dip-slope, on a gently in-clined layer of resistant rock, on the other.

CULTURE (CARTOGRAPHIC) – Man-madeor artificial features of the terrain. (JD)

CUP ANEMOMETER — A rotation anemom-eter whose axia of rotation is vertical. Cupanemometers usually consist of three orfour hemispherical or conical cups mountedwith their diametrical planes vertical and

●distributed symmetrically about tbe axis ofrotation. The rate of rotation of the cups,

MlL-STD-l 16525 .MARCH1968

which is a measure of the wind speed, is de-termined indirectly by gearing a mechan-ical or electrical counter to the shaft.(AMS)* ‘

CURRENT, n.—l. A horizontal movement ofwater. (NOO) 2. Air in essentially verticalmotion, ”usually called air CWTsmt. (ND) ●

3. ,~e flowing of liquids, gases, pati]cles,or electrons, in conductors.

CUTOFF, n.— A new and relatively shortchannel formed when a stream cub throughthe neck of an oxbow or horaeshce bend.(GS)

CYCLE, n.— The complete range of states orvalues through which a phenomenon or per-iodic function passes before repeating itselfidentically. (1S0)

CYCLIC SALT — Salt deposited on the soilby wind blowing off the sea or off inlandsalt lakes. (SSS)

CYCLING, n.— A type of vibration testingin which the applied frequency is period-ically increased and decreased between twofrequency limik, the rate of change of fre-quency being a particular function of timeor frequency.

CYCLING, LINEAR — A type of CYCLINGin which the rate of change of frequency isproportional to time. An equal time ia spentat all frequencies in the range of interest.

CYCLING, LOGARITHMIC — A type of CY-CLING in which the rate of change of fre-quency ia proportional to the frequency. Anequal time is spent between half powerpoints for resonant systems of equal trans-missibility.

CYCLING, LOG-LOG —A type of CYCLINGin which the rate of change of frequency isproportional to the square of the frequency.An equal number of vibratory atress re-versals is generated between half powerpoints for resonant systems having equaltransmissibility.

CYCLONE, n.— A closed system of low at-mospheric pressure around which the winds

39


..<MlL-STD-l 165 ~ , -25 MARCH1.968 I

+’

blow counterclockwise i.g.Ahenorthern hemi-sphere, and cfockwise ii ‘the southern hemi-sphere. Because cyclones nearly always are~ccompan iedby inclement !vealhcr, they arcfrequently referred 10 simply as storms.(Ahfs)*

D

DAILY MEAN—1. The average value of ameteorological element over a period oftwenty-four hours. The “true daily mean”is usually taken as the mean of twenty-fourhourly values between midnight and mid-night, either as continuous values takenfrom an mltographic record or as pointreadings at hourly intervals, When hourlyvalues are not available, approximationsmust be made from observations at fixedhours. (AMS)* 2. The long~period meanvalue of a climatic element on a given dayof the year. (AMS)*

DAMAGE SUMMATION—An analytic proc-ess in which the assumed or measured phys-ical parameters of the materials and me-chanical structure of a system, and of thefatigue-producing energy applied to the sys-tem, are analyzed to establish a relationshipbetween damage accumulation and time, orto predict the time to failure.

DAMP HAZE — Small water droplets or veryhydroscopic particles in the air, reducingthe horizontal visibility somewhat, but tonot less than 11A miles. Damp haze ia simi-lar to a very thin fog, but the droplets orparticles are more scattered than in lightfog and presumably smaller. ( ND)

DAMPING, n. — The dissipation of energywith time or distance. such as the effect offriction or its equivalent in reducing oscilla.tion of a system. Other types include coul-omb, viscous, structural, eddy-current, non-]inear, material, interface, and tuned dy.namic damping.

DAMPING CAPACITY — The ability of amaterial to absorb vibrations by changingthe mechanical energy into heat,

DAMPING COEFFICIENT —The ratio of a

force applied to a viscous damper to the rel-ative velocity between its connecting points,(sVII)

DAMPING, CRITICAL — The minimum vis.cous damping that will allow a displacedsystem to return to its initial position with-out oscillation. (SVH)

DAMPING RATIO — See FRACTION OFCRITICAL DAMPING

DAY WITH PRECIPITATION —A day inwhich the total precipitation received equalsor exceeds a specified amount (in U.S., w,a-ter equivalency - .01 in.).

DEBACLE, n. — 1. The rush of water or icein a stream immediately following theBREAKUP. (NOO) 2. Any violent rush orflood of water. ( ND)

DEACTIVATION, n.— 1. Mekdlurgy, Theprocess of prior renloval of the active cor-rosive constituents, usually oxygen, from acorrosive liquid by controlled corrosion ofexpendable metal or by other chemicalmeans. 2. Act of rendering explosives inert.(AD)

DEAD SPACE — 1. An area within the maxi-mum range of a weapon, radar, or observer,which cannot be covered by fire or observa-tion from a particular position because ofintervening obstacles, the nature of theground, or the characteristics of the tra-jectory, or th> limitations of the pointingcapabilities of the weapon. (JD) 2, An areaor zone which is within range of a radiotransmitter, but in which a signal is not re-ceived. (JD) 3. The volume of space aboveand around a gun or guided missile systeminto which it cannot tire because of me-chanica! or electrot]ic Iilnitations, (JD)

DEBRIS, n.-– .%:)yaccumulation of loose ma-terial result lr,~ iiwm the dec:ty and disinte.gration of rocks. 1: t,n]sists of rock frag.ments. sand, e;irth, and sometimes organicmatter. When occurrinx at the foot of asleep slope it is identified as TALUS. Theterm is also applied specifically to the wastesilt, sand, and gravel produced by hydraulicoperations. (S&V)”

40


. . ..

e DEBRIS ICE — Ice which contains mud,stones, shells, etc. Also called muddy ice.(ND)

DECAY, n.— 1. The decomposition of woodsubstance by fungi. Two stages of decay,the incipient and advanced stages, are or-dinarily recognized, though two supplemen-tal ones, the intermediate and final stages,are sometimes given recognition. (SAF)2. Rotting or rotted wood. (SAF) 3. Thedecrease in the energy of anything afternew energy ceases to be SUPPIied, as in thecase of wind waves after the wind ceases toact. (ND)

DECAY CURVES (RADIOACTIVE) —Graph lines representing the decrease ofradioactivity with the passage of time.(JD)

DECAY (RADIOA~IVE)— The decrease intbe radiation intensity of any radioactivematerial with respect to time. (JD)

DECAY RATE (RADIOACTIVE) — 1. The,,--

“0

time rate of the disintegration of radioac.tive material generally accompanied by theemission of particles or gamma radiation.(JD) 2. The rate of disintegration of radio-active material with respect to time. (JD )

DECIBEL, n.— (See BEL) — 1. In general,a unit which denotes the magnitude of aquantity with respect to an arbitrarily es-tablished reference value of the quantity interms of the logarithm (to the base 10) ofthe ratio of the quantities. (SVH) * !?. AUnit for expressing the loudness Of sOunds,one decibel being approximately the leastchange detectable :by the average humanear. The difference in decibels of two soundsis exactly equal to 10 times the commonlogarithm of the ratio of their powers.(ND)

DECIDUOUS, adj. — In botany, losing theleaves during a certain period of the year,generally either the cold season or dry sea-son.

DECLIVITY, n.— A descending slope, as op-

,0

,,... posed to ACCLIVITY, (GS)

41


DECOMPOSITION, n.— The chemical sepa-ration of a substance into two or more sub-stances, which may differ from each otherand from the original substances,

DECOMPRESSION, n.— The act or processof lowering the air pressure within a cabin,chamber, etc., or of subjecting to, or under-going, a decrease in air or atmospheric pres-sure. (NASA)

DECONTAMINATION, n.— The process ofmaking any person, object, or area safe byabsorbing, destroying, neutralizing, mak.ing harmless or removing, chemical or bio-logical agents, or by removing radioactivematerial clinging to or around it. (JD)

DEEP FORDING — The ability of a gun orvehicle equipped with built-in waterproof-ing with its suspension in cbrrtact with theground to negotiate a water obstacle by ap-plication of a special waterproofing. (JD)

DEFILE, n. — A deep, narrow mountain pass.(GS)

DEFILADE, n.— 1. Protection from hostileground observation and fire provided by anobstacle such as a hill, ridge, or bank. (JD)2. A vertical distance by which a positionis concealed from enemy observation. (JD)

DEFILADE, v.— To shield from enemy fireor observation by using natural or artificialobstacles. (JD )

DEFLATION, n.— The removal of fine soilpatiicles from soil by wind. (SSS)

DEFOLIANT, n.— A chemical used to re-move prematurely the leaves from plants.(AD)

DEFOLIATE, v.t. — To cause a tree or otherplant to lose ita leaves.

DEGRADATION — Deterioration, usually inthe sense of a physical or chemical processrather than a mechanical ,me. There may be.a specific amount of degradation permittedas a result of performance of environmentaltesting.

DEGREE DAY — 1. Gener*!ly, a measure ofthe departure of the mean daily tempera-ture from a given standard: one degree day



for each degree (“C or “F) of departureabove (or below) the standard during oneday. Recently, degree days have been ap-plied to fuel and power consumption, withthe standard being 65° F. (AMS)” 2. ASused by U. S. Army Corps of Engineers, de-gree days are computed as departure aboveand below 32° F, positive if above and neg-ative if below. Also called freca”nu degree-dny. (AMS)”

DEGREES-OF-FREEDOM — In a mechani-cal system, the minimum number of inde-pendent coordinates required to define com-pletely the positions of all parts of the sys-tem at any instant of time. In general, it isequal to the number of independent dis-placement that are possible. (SVH)

DEGREE HOUR — As used by the U. S.Army Corps of Engineers, the departure(in “F) of the hourly temperature from astandard of 32° F, positive if above and neg-ative if below. Degree hours may be accum-ulated (summed) over any period of time,depending upon the use to which they areapplied. (AMS )

DEGREES OF FROST — The number of de-grees that the temperature falls below 32°For O“C, tbe freezing point. (ADT)

DEHUMIDIFICATION, n.— The condensa-tion of water vapor from air by cooling be-low the dew point, or removal of water va-por from air by chemical or physical (ad-sorption) methods.

DEHUMIDIFY, v.t. — To reduce, by anyprmxss, the amount of water vapr in aspace.

DEICING, ri. — The removal of ice accumula-tion on aircraft, ships, and other objects byice pick, shovel stezm jet, chemical treat-ment, mechanical devices, etc. (IG)

DELAYED FALLOIJT — Fallout resultingfrom high-yield atomic or thermonucleardetonations which thrust their clouds intothe stratosphere. Storage times vary fromless than one year to as high as 10 years, de-

pending upon the’ latitude and altitude ofdetonation. The particles are of sub-micronsize (AMS) *

DELIQUESCENCE, n.–- The change under-gone by certain substances which becomedamp and finally liquefy when exposed tothe air, owing to the very low vapor pres-sure of their saturated solutions.

DELTA, n.— A deposit of alluvium at themouth (s) of a river. The term refers par-ticularly to that part of the deposit forminga tract of land above water, usually roughlytriangular in shape, as the Greek letter~.(ND) *

DENDRITIC DRAINAGE — A drainagepattern in which streams run in many di-rections and branch irregularly like a tree.The positions of the streams are not influ-enced by differences in rock structure orhardness. (S&V)

DENSITY — 1. Sod Mechania. The unitweight of a soil in pounds per cubic foot.The type of density, i.e., natural or in place,wet, dry, remolded natural, relative, etc.,should be specified. (BR ) 2. Oceanography.The equivalent of specific gravity, or theratio, at atmospheric pressure, of the weightof a given volume of sea water to that of anequal volume of distilled water at .i.OaC.(39.2” F.) . (NOO)

DENSITY ALTITUDE — The height abovesea level at which the existing density ofthe atmosphere would be duplicated in thestandard atmosphere; atmospheric densityexpressed as height according to a standardscale. (ND)

DEPOSIT, n.— Material left in a new posi-tion by a natural transporting agent such aswater, wind, ice, or gravity, or by the activ.ity of man. (SSS)

DEPOSIT ATTACK — Corrosion occurringunder or around a discontinuous deposit ona metallic surface. ( ECS)

DEPRESSION, n.— 1. Meteorot. An area oflow pressure; a low or a trough. This is us-

42


ually applied to a certain stage in the devel-opment of a tropical cyclone, to migratorylows, and troughs, and to upper-level lowsand trou”ghs that are only weakly developed.(AMS) * 2. GPomorph. A low place of anysize on a plain surface, with drainage un-derground or by evaporation; a hollow com-pletely surrounded by higher ground andhaving no natural outlet for surface drain-age. (GS)

DESERT, n.— A region where precipitationis insufficient to support any plant life ex-cept xerophilous vegetation; a region ofextreme aridity. W. Koeppen, in his climaticclaeaificstion, defines a desert CLIMATE(designated BW) by assigning maximumvalues of annual precipitation as follows:for precipitation mainly in cold season,

P -0.22 (t-32) ;for evenly distributed precipitation,

p = 0.22 (t—19.4) ;for precipitation mainly in the hot season,

P -0.22 (t—6.8) ;

‘owhere p is the mean annual precipitation ininches, and t is the mean annual tempera-ture in ‘F. (AMS) *

DESERT CRUST — A hard layer, contain-ing calcium carbonate, gypsum, or otherbinding material, exposed at the surface indesert regions. (SSS)

DESERT FLATS — The essentially flat sur-face extending from the edges of PLAYASto the ALLUVIAL FANS or BAJADAS.

DESERT PAVEMENT — A mosaic of close-ly packed pebbles and broken rock frag-ments usually coated with a stain or cruslof manganese or iron oxide (see DESERTVARNISH) and caused by wind removal ofsand, silt, and clay particles. See REG.

DESERT SOIL — A zonal great soil groupconsisting of soils with a very thin, light-colored surface horizon, which may be ves-icular and is ordinarily underlain by cal-careous material; formed in arid regionsunder sparse shrub vegetation. (SSS)

●DESERT VARNISII — A glossy sheen or

43


coating on stones and grsvel in arid regions.’(sss)

DESICCANT, n.— A drying or dehydratingagent which absorbs water vapor by physi-cal or chemical means.

DESICCATOR, n.— An enclosed apparatusin which substances can be kept in a dryatmosphere. The latter is obtained by the in-clusion of drying agents such as phosphoruspentoxide or concentrated sulphuric acid.

DETECTOR, INFRARED — A device forobeerving and measuring infrared radia-tion, such as the Iwlometer, radiomicrome-ter, therrnopile, pneumatic cell, photocell,photographic plate, and photoconductivecell.

DETERIORATION, n.— 1. The loss, in thevalue of a material or a decrease in the abil-ity of a product to fulfill the function forwhich it was intended. 2. A process of tran-sition from a higher to a lower energy level.

DETERIORATION PATTERN — L]sting ofthe various aetenoration processes noticedon an item .in the order of their intensitiesor rates of progress or in the order of theirdeterioration potentials.

DETERIORATION POTENTIAL — Theminimum change resulting from a deterior-ation prbcess which affects the suitabilityof the item to serve ita intended purpose.

DETERIORATION PROCESS-Any changein physical characteristics or any chemicalreaction occurring as the result of the stor-age or use of an item. As a rule, a deterior-ation process is the result of the environ-mental exposure of the item. It can also begenerated by internal conditions and pro-moted by the environmental stresses.

DETERIORATION PRODUCT — New orchanged compounds formed as a result of aparticular deterioration proce.w.

DETERIORATION RESISTANCE — Theability of an item to withstand the effectsof environmental exposures and to prevent



deterioration which might result from in-ternal item conditions.

DETERIORATION-RESISTANT P R O D -UCTS — The product designs which pre-vent undesirable deterioration during theirprescribed useful life spans.

.,

DETRITUS, n.— An accumulation of thefragments resulting from the disintegrationof rocks. (ND)

DEW, n. — Water condensed onto grass andother objects near the ground, the tempera-tures of which have fallen below the DEWPOINT of. the surface air due to radiationalcooling during the night, but are still abovefreezing. If the temperature falls belowfreesing after dew has formed, the frozendew is known as white dew. (AMS) *

DEW CELL — An instrument used to deter-mine the DEW POINT. It consists of apair of spaced bare electrical wires woundspirally around an insulator and coveredwith a wicking wetted with a water solutioncontahring an excess of lithium chloride. Anelectrical potential applied to the wirescauses a flow of current through the lithiumchloride solution which raises the tempera-ture of the solution until its vapor pressureis in equilibrium with that of the ambientair. (AMS) *

DEW POINT — The temperature to which agiven weight of air must be cooled at con-stant pressure and constant water-vaporcontent in order for S.\ TURATION to oc-cur. When this temperature is below 0’ C,it is sometimes called the frost poip L(AMS) *

DIAMETER, BREAST HIGH — The diam-eter of a tree at 4.5 feet above averageground level, except that in National Forestpractice it is measured from the highestground level. Abbreviated d.b.h. The addi-tional abbreviations o.b. and Lb. are usedto designate whether the diameter refers tcthe measurement outside or inside the bark.(SAF)

DIATOM, n.— One of a class of microscopic

phytoplankton organisms, possessing a wallof overlapping halves (valves) impregnated ● :with silica”. Diatoms are one of the mostabundant groups of organisms in the seaand the most important primary food sourceof marine animals. (NOO)

DIATOMACEOUS EARTH — A geologic de-posit of fine, grayish siliceous material com-posed chiefly or wholly of the remains ofdiatoms. It may occur as a powder or as atirous, rigid material. (SSS)

DIFFRACTION, n. — 1. The bendin”g of therays of radiant energy around the edges ofan obstacle or when passing near the edgesof an opening, or through a small hole orslit, resulting, in the case of light, in theformation of a spectrum or alternate lightand dark bands. (ND) 2. The bending of awave as it passes an obstruction. (ND)

DIFFRACTION ZONE — With respect toradio propagation, that portion of any prop-agation path which lies below a line-of-sightpath. It is generally applied to the regionbelow the earth’s radio horizon and, in thiscase, is often referred to as the earrh shad- ●OW. Energy enters this zone by diffractionand scattering processes; and the interfer-ence lobes produced by the addition of thedirect and surface-reflected waves for [ine-of-sight conditions are not present. (AILS)

DIFFUSE SKY RADI.ATION (or SKY.LIGHT) — Radiation reaching the earth’ssurface after having been scattered fromthe direct solar beam by molecules or sus.pensoids in the atmosphere. Of the totalii~ht removed from the direct solar beam byscattering in the atmosphere (approximate-ly 2L percent of the incident radiation),about two-thirds ultimately reaches theearth as diffuse sky radiation. (AMS) ‘

[) IF FUSIOIN, a.–. The spreading out or scat-tering of anything. For example, light isd; fiused wh(:n reflected t’rom a rough ~ur-face. (ND)

DIKE, n.— 1. G,cl. A sheet-like body of igne-ous rock that tiils a fissure in older rocks

44


* which it entered while in a molten condi-tion. Dikes occur in all types of material,igneous, metamorphic, and sedimentary; ifin scrXmentary rocks or bedded volcanicrocks, they “cut” the formations or tran-sect th,e beds at an angle. Dikes vary fromleas than an inch in width and a few yardsin length to thousands of feet in width andmany miles in length. (S&V)’ 2. Civil En-gineering. A bank of earth, stones, etc., con-structed to prevent low-lying land frombeing inundated by the sea, a river, etc.

DIPCOAT, n.— A method of applying a pro-tective or decorative coating to an articleby dipping the piece into the coating ma-terial.

DIRECT SHEAR TEST — Soil Mechanics.A“test to determine the maximum shearingstrength and angle of friction of soils forIuse in stability analyses,

DIRECTION OF CURRENT — The direc-tion toward which a current is flowing,

●called the set of the current. (ND)

DIRECTION OF WAVES — The directionfrom which waves are moving. (ND) ●

DIRECTION OF WIND — The directionfrom which a wind is blowing. (ND)

DIRECT RUNOFF ——The runoff enteringstream channels promptly after rainfall orsnowmelt. Superposed on base runoff, itforms the bulk of the hydrography of a flood.(MH)*

DIRECT SOLAR RADIATION — In acti-nometry, that portion of the radiant energyreceived at the instrument or pyrheliometer“direct” from the sin, as opposed to DIF-FUSE SKY RADIATION, effective terres-trial radiation, or radiation from any othersource. (AMS) *

DISINTEGRATION, NUCLEAR — A UU-clear transformation characterized by theemission of mass and energy from the nu-cleus. If the emission is spontaneous, it issaid to be radioactive; if the disinte~ration

a results from collision, it is said to be in-

MIL-STD-l 1651S MARCH1968

duced. When numbers of nuclei are in-volved, the process is characterized by a def-inite HALF-LIFE.

DISINTEGRATION RATE – 1. Theabsolute rate of decay of a radioactivesubstance, usualfy expresssd in terms ofdisintegration per unit of time. 2. Theabsolute rate of the transformation of anuclide under bombardment.

DISPERSION, n.- 1. The process in whichradiation is separated into its componentwavelengths. Dispersion results when anoptical process, such as diffraction, refrac-tion, or scattering, varies according towavelength. (AMS ) * 2. The rate of changewith wavelength of the index of refractionof any refractive interface or discontinuity.(AMS) *

DISPLACEMENT — A vector quantity thatspecifies the change of position of a bodyor particle and is usually measured from themean position or position of rest. In gen-eral, it can be represented as a rotation vec-tor or a translation vector, or both. SeeAMPLITUDE, PEAK TO PEAK, (SVH) *

DISPLACEMENT PICKUP — A devicewhich converts a detectable change in amedium, such as that produced by a soundwave or an electroma~etic wave, into someform of electrical energy.

DISTURBED ICE — Any land ice which iabroken by pressure into a chaotic patternof elevations and depressions. (ND)

DITHER, n.— A signal of controlled ampli-tude and frequency applied to ,the servomotor operating a transfer valve, such thatthe transfer valve is constantly being “quiv-ered” and cannot stick at its null position.

DIURNAL, adj. — Daily, especially pertain-ing to actions which are completed withintwenty-four hours and which recur everytwenty-four hours; thus, most reference ismade to diurnal cycles, variations, ranges,maxima, etc. (AMS)”

DIVIDE, ]i. — The line of separation between

4s



drainage sytems; the summit of an inter-fluve. The highest summit of a pass or gap.(m)

DOPPLER EFFECT — The phenomenon evi-denced by the chang~ in the observed fre-quency of a sound or radio wave caused bya time rate of change in the effective lengthof the path of travel between the source andthe point of observation. (JD)

DOSAGE (RADIATION) — The amount ofnuclear radiation received by a person un-der a ~ven set of circumstances. ,

DOSE (RADIATION) — Properly, the ab-sorbed dose from any ionizing radiation.Sometimes refers to the exposure dose,properly expressed in roentgens, which isa measure of the total amount of ionizationthat x-rays or gamma rays produce in theair. Sometimes improperly used for radia-tion outside the applicability of the roent-gen, as the ionization which would be pro-duced in air. It is more advisable to restrictthe term to the absorbed dose, commonlygiven in RADS.

DOSIMETER, n.— An instrument for meas-uring and registering total accumulated ex-posure to ionizing radiations.

DOSIMETRY, n.— The measurement of ra-diation doses. It applies to both the devicesused (dosimeters) and to the techniques.(JD)

DOTE, n. — An early stage of DECAY. It isusually characterized by a change in colorof the wood in patches or streaks whichmay be lighter or darker than normal.(SAF)

DOWNWASH — The downward flow of gasesunder pressure resulting from the applica-tion of power to the lifting or propelling, orboth, of airborne vehicles, vertiplanes, heli-copters, rockets, guided missiles, etc. (AD )

DOWNWIND, adj. & adv. — In the directiontoward which the wind is blowing. The termaPPlies pa~icularly tO the situation of mov-ing in this direction, whether desired or

not. Before the wind implies assistancefrom the wind in making progress in a de-sired direction. Leeward applies to the di:rection toward which the wind blows, with- 0

out implying motion. The opposite is up-wind. (ND)

DRAG, n.— The frictional impedance offeredby a fluid to the motion of lwdies passingthrough it; more precisely, the componentof aerodynamic or hydrodynamic force par-allel to’the direction of mean flow. (AMS) *

DRAINAGE AREA — The area, measured ina horizontal plane, which is enclosed by aDRAINAGE DIVIDE. (MH) “

DRAINAGE BASIN —A part of the surfaceof the earth that is occupied by s drainagesystem, which consisb of a surface streamor a body of impounded surface water to-gether with all tributary surface streamsand bodies of impounded surface water.(MH)

DRAINAGE DIVIDE — See DIVIDE.

DRAW — A shallow DRY WASH or AR-ROYO, characterized by low banks whichare gentler than those of the wash or ar- ●royo.

DRIFT, n. — 1. The effect of the velocity offluid flow upon the velocity (relative to afixed external point) of an object movingwithin the fluid; the vector difference b.tween the velocity of the object relative tothe fluid and its velocity to the fixed refer-ence. (NOO) 2. To the mariner, drift is thespeed of a current of ice floe usually given innautical miles per day or in knots. (NOO) *3. To the oceanographer, drift is a wide,slow-moving current principally caused bywinds. (NOO) 4. The component of an air-craft’s giound speed perpendicular to theheading. (ND) 6. Material “moved from oneplace and deposited in another, as sand bya river, rocks by a glacier, material washedashore and left stranded, snow or sand piledup by wind. (ND) * 7. Gradual movementfrom a set position, as of a control by vi-bration. ( ND) 8. The change of frequency

46


in an oscillator during warm-up. (ND)9. The horizontal component of precessionor wander, or the algebraic sum of the two.When it is desired to differentiate betweenthe sum and its components, the sum iscalled total drift. (ND)

DRIFT, GLACIAL—All rock material intransport by glacier ice, all deposita madeby glacier ice, and all deposik predomi-nantly of glacial origin made in the sea orin bodies of glacial melt water, includingrocks rafted by icebergs. Glacial drift oc-curs as scattered rock fragments, as tiU,and as outruaa%. (ADT)

DRIFTING SAND — An ensemble of parti-cles of dust or sand raised from the groundto small or moderate height by a sufficientlystrong and turbulent wind. (WMO) *

DRIFTING SNOW — Snok particles beingblown about close to the ground (leas than 6feet above the surface), differing fromblowing snow in that vertical visibility isnot appreciably affected. (ADT) ●

‘DRIZZLE, n.— Fairly uniform precipitationcomposed exclusively of fine drops of water(diameter leas than 0.5 mm or 0.02 in.),very close to one another. (WMO) *

DROPLET (or DROP) — A small sphericalparticle of any liquid; in meteorology, par-ticularly a water droplet. There is no definedsize limit separating-droplets from drops ofwater, but it is sometimes convenient to de-note two disparate size rangee, such as theoft-used distinction of liquid cloud parti-cles (droplets) from liquid precipitation(drops), thereby implying that a maximumdiameter of 0.2 mm is the limit for droplets.(AMS)

DROP TEST — A type of shock test in whicha test specimen, or a guided structure towhich the specimen is mounted, is rekaaedfrom a specified height and after free fall isdecelerated by a specified medium.

DROSOMETER, n.— An instrument used tomeasure the amount of dew formed on a


given surface. (AMS) *

DROWNED VALLEY — A valley, the lowerpart of which has been inundated by the seaas a result of submergence of the land mar-gin.

DRUMLIN, n.— A smcoth oval hill of glacialorigin. Drumlins are compxad almost ex-clusively of boulder clay but sometimes in-clude Ienslike masses of gravel and sand,and are thus mainly constructional in ori-gin. They range in length from a few hun-dred feet to more than a mile, and in heightfrom 25 to about 200 feet. They are steep?ron the end of ice approach and taper off toa slender low paint on the lee side, thushaving a long axis in the direction of icemovement. (S&V)

DRY AIR — 1. In atmospheric thermodyna-mics and chemistry, air that contains no wa-ter vapor. (AMS) 2. Generally, air withlow relative humidit~. (AMS)

DRY-BULB TEMPERATURE — The tem-perature of the air. (AMS) *

DRY-BULB THERMOMETER — A ther-mometer with an uncovered bulb, used witha wet-bulb thermometer to determine atmo-spheric humidity. The two thermometersconstitute the essential parts of a PSY-CHROMETER. (ND)

DRY COLD — See COLD DRY.

DRY FOG — A fog that does not moisten ex-posed surfaces. (AMS)

DRY WASH _ A broad, dry bed of a stream;a dry stream channel. (GS) ●

DUMMY LOAD — See MOCKUP.

DUNE, n.— 1. A heap of sand or other ma-terial accumulated by wind. The externalform may be that of a hill or ridge. 2. Asand wave of approximately triangularcross stilon (in a vertical plane in the di-rection of flow) with gentle upstream slopeand steep downstream slope, which travelsdownstreani by the movement of the sedi-

47


Ml&TD-1 16525 M RCH 1968

?men\} UP the upstream slope and the deposi-tion of it on the downstream slope. Forlypes,” see BARCHAN, LONGITUDINALDUNE~ STAR DUNE, TRANSVERSE“DUNE; .WHALEBACK, and smF mm.

DUST, n.— 1. Solid materials suspended inthe atmosphere in the form of small irregu-lar particles, many of which are micro-scopic size. Dust is due to many natural andartificial sources: volcanic eruptions, saltspray from the seas, blowing solid particles,plant pollen and bacteria, smoke and ashesof forest fires and industrial combustionprocesses, etc. (AMS)” 2. Particles smallerthan 75 microns in diameter.

DUST STORM — An unusual, frequently se-vere weather condition characterized bystrong winds and dust-filled air over an ex-tensive area. A thick mass of airborne dustmay obscure the atmosphere to the extentthat it reduces visibility very considerably— sometimes practically to zero. (AMS) ‘“

DUST WHIRL — A rapidly rotating columnof air, usually about 100 to 300 feet inheight, carrying dust, straw, leaves, orother light material. It has no direct rela-tionship to a dust storm, and usually de-velops on a calm, hot afternoon with clearskies, mostly in desert regions. (ND)”Also called dust derA

DYNAMIC AGING, n.- Accelerated agingof rubber in the, presence of dynamicstresses, in which strain exposes new areasof the molecular structure to attack, theresulting cracks being caused by a com-bination of dynamic fatigue and oxidationor ozone attack. (SVH)

DYNAMIC DEHUMIDIFICATION - Theremoval of moisture from the atmosphereby dehumidification machines that usepow’er-driven blo;vers.

DYNAMIC METEOROLOGY — The branchof meteorology which deals with the mo-tions of the atmosphere and their relationsto other meteorological elements. (ND)

DYNE, n.- A unit of force which will pro-duce an acceleration of one centimeter persecond if applied to a body with a mass ofone gram.

E

EARLY FALLOUT — Fallout near the siteof an explosion.

EARTH, n.— 1. The solid matter of theglobe as contrasted with water and air.(S&V) 2. The loose or softer materialcomposing part of the surface of the globe,aa distinguished from firm rock. (S&V)

EARTHQUAKE, n.— A perceptible trem-bling to violent shaking of the ground pro-duced by the sudden shift of part of theearth’s crust.

EBB CURRENT — The tidal current associ-ated with the decrease in the height of atide. Ebb currents generally set seaward,or in an opposite direction to the tideprogression. Erroneously called ebb tide.(NOO)

ECHO, n.— The signal received by a radaror sonar set as a result of the reflection ofa transmitted radio or sound pulse fromobjects in the field of scan. {AD)

ECHO FLUTTER — A rapid succession ofreflected pulses resulting from a singleinitial pulse.

ECOLOGY, n. — The science that dealswith the interrelations of organisms andtheir environment. (SSS)

EDAPHIC, adj. — 1. Of or pertaining to thesoil. (SSS) 2. Resulting from” or influencedby factors inherent in the soil or othersubstrate, rather than by climatic factors.(sss)

EDDY, n. — A current of air or fluid thatruns contrary to the main stream, espe-cially a small vortex of air that runscounter to the main airflow. Eddies tend t~j

48



e form on the lee side of an object. (AFD)’

EFFECTIVE GUST VELOCITY—The ver-tical component of the velocity of a sharp-edged gust that would produce a givenacceleration on a particular airplane flownin level flight at the design cruising speerlof the aircraft and at a given air density.(AMS)

EFFECTIVE PRECIPITATION — 1. Thatpart of the precipitation that produces run-off. (MH) 2. A weighted average of cur-rent and antecedent precipitation that is“effective” in correlating with runoff.(MH) 3. As described by U. S. Bureau ofReclamation, that part of the precipitationfalling on an irrigated area that is effectivein meeting the consumptive use require-ments. (MH)

‘ EFFECTIVE SOUND PRESSURE (orROOT-MEAN-SQUARE SOUND F’RES.SURE) — The effective sound pressure ata point ia the root-mean-square value ofthe instantaneous sound pressures over atime interval at the point under considera-tion. In the case of periodic sound pres.sures, the interval must he an integralnumber of periods or an interval that islong compared to a period. In the case ofnonperiodic sound pressures, the intervalshould be long enough to make the valueobtained essentially independent of smallchanges in the length of the interval. Theterm eflective sound pressure is frequentlyshortened to sound pressure. (ASA)

EFFECTIVE TEMPERATURE “— 1. Thetemperature at which motionless, saturat-ed air would induce, in a sedentary workerwearing ordinary indoor clothing, thesame sensation of comfort as that inducedby the actual conditions of temperature,humidity, and air movement, (AMS)” 2.With respect to radiation, ascribed to al}imperfectly radiating body: the tempera-ture at which a perfect radiator (blackbody) would emit radiation at the samerate. Thus, the effective temperature isalways less than the actual temperature.

(AMS) 3, Phenol, The temperature atwhich plants, especially cereals, begin togrow. (AMS)

EFFECTIVE TERRESTRIAL RADIATION— The difference between the outgoing(positive) terrestrial radiation of theearth’s surface and the downcoming (neg-ative) counterradiation from the atmos-phere. It is to be emphasized that this rlif-ference is a positive quantity, of the orderof several tenths of a Iangley per minute,at all times of day (except under condi-tions of low overcast clouds). It typicallyattains its diurnal maximum during themid-day houra when high soil temperaturescreate high rates of outgoing terrestrialradiation. However, in daylight hours theeffective terrestrial radiation is generallymuch srrjaller than the insolation, while atnight it~ typically dominates the energybudget of the earth’s surface. (AMS) *

ELASTICITY, n.— That property of a ma-terial by virtue of which it tends to auto-matically recover its original size andshape after deformation.

ELECTROLYTIC PROTECTION — Protec-tion from electrochemical corrosion by useof the protected material as cathode in thecorrosion cell. If an electromotive forcecounter to the normal flow of current in acorroding system can be impressed on thesystem circuit, the tendency for the anodicmetal to go into solution will be decreased.

ELECTROMAGNETIC, adj.—Pertaining tothe combined electric and magnetic fieldsassociated with radiation or with move-ments of charged particles.

ELECTROMAGNETIC LINE-OF-SIGHT—The maximum distance at which directwave transmission is possible betweentransmitting and receiving antennas ofgiven height, neglecting propagation anom-alies.

ELECTROMAGNETIC RADIATION — En-ergy propagated through space or throughmaterial media in the form of an advanc-

49


A41L-STD-1 16525 MARCH 1968

ing disturbance in electric and magneticfields existing in space or in the ,media. Theterm radiation, alone, is used commonlyfor this type of energy, although it actuallyhas a broader meaning. (AMS) *

ELECTROMAGNETIC SPECTRUM—Theordered array of all known electromag-netic radations, extending from the short-est gamma rays through x-rays, ultra-violet radiation, visible radiation, infraredradiation, and including microwave andall other wavelengths of radio energy.(AMS)*

ELECTROMECHANICAL COUPLINGFACTOR—A factor used to characterizethe extent to which the electrical charac-teristics of a TRANSDUCER are modifiedby a coupled mechanical system, and viceverea. (SVH)

ELECTROMETEOR, n.— A visible or au-dible manifestation of atmospheric elec-tricity. Electrometers either correspondto discontinuous electrical discharges(LIGHTNING, THUNDER) or occur asmore or less continuous phenomena(SAINT ELMO’S FIRE, polar aurora).(WMO)

ELECTRONIC JAMMING - The deliberateradiation, reradiation, or reflection of elec-tromagnetic signals with the object of im-pairing the use of electronic devices’ bythe enemy. (JD)

ELECTRONICS, n.— The broad field per-taining to the conduction of electricitythrough a vacuum, through gases, orthrough solids, and circuits , associatedtherewith.

ELEVATION — The vertical distance ofground forms, usually measured in feet ormeters, above mean sea level (plus eleva-tion) or below mean sea level (minus ele-vation). (JD)

EMANOMETER, n.—An instrument for themeasurement of the radon content of theatmosphere. Radon is removed from asample of air by condensation or adsorp-

tion on a surface, and is then placed in anionization chamber and its activity de-termined. (AMS)

EMBAYED COAST — A coast with manyprojecting headlands, bays, and outlyingislands. (S&V)”

EIMBRITTLEMENT— An increase in the sus-ceptibility of a metal to fracture understress caused by the introduction of gasor other foreign atoms, by segregation .ofbrittle constituents, by internal oxidation,or by certain types of corrosion.

EMISSIVITY, n.— The ratio of the rate ofemission of radiant energy in a givenwavelength interval from a given surfaceto the rate of emission of a blackbody atthe same temperature in the same wave-length interval with the radiation emittedby the surface is due solely to its tempera-ture (i.e. excluding transmitted radiation,heat generated by chemical or other reac-tions, etc. )

EMITTANCE — A synonym for EMISSIVI-TY, especially in infrared technology.

END MORAINE — See TERMINAL MOR- 0AlNE.

ENTRAINMENT, n. — In meteorology, themixing of environmental air into a pre-existing organized air current so that theenvironmental air becomes part of the cur-rent; the opposite of detrain?nent. (AlIS)

ENTROPY — I. A measure of the unassail-ableenergy in a system, that is, energy thatcannot be converted into another form ,otenergy. 2. A measure of the degree of mix-ing of different kinds or sizes of sedi-ments; high entropy approaches an lun-mixed sediment of one kind. (NOO)

ENVANAL, n.— An empirical method ofrecording data that reflects the perform-ance of equipment and material when oP-erated under various world-wide condi-tions. It is formed from a contractionthe words environment and analysis.

ENVIRONMENT, u, — 1. The totality

of

of

50


‘a natural and induced conditions occurringor encountered at any one time and place.2. The integrated total of all stresses whichinfluence the performance capability ofman and equipment during transit, instorage (or confinement) or under fieldoperating conditions. (AR) See also AR-TIFICIAL ENVIRONMENT, INDUCEDENVIRONMENT, NATURAL ENVI-RONMENT, OPERATIONAL ENVIRON-MENT.

ENVIRONMENTAL CONTROPA methodby which the severity of a damaging en-vironmental stress is reduced to a leveltolerable by equipment or personnel.

ENVIRONMENTAL DESIGN CRITERIA—Environmental parameters which repre-sent a given degree of severity of condi-tions existing in nature,, in equipmentoperation, or in storage, which are to beincorporated in the design of equipment.

ENVIRONMENTAL ELEMENT — An EN.VIRONMENTAL FACTOR.

ENVIRONMENTAL ENGINEERING —That branch of engineering concerned withthe designing, developing, and testing ofequipment or materials to function reliablyunder all environmental conditions ex.petted during their intended operational,transportation, or storage life.

ENVIRONMENTAL FACTOR—One of thecomponents of an environment; an envir.onmental element. Environmental factorsmay be either (a) induced, including thoseconditions resulting from the operation ofa structure or item of equipment, or (b)natural, including those conditions gener-ated by the forces of nature and whoseeffects are experienced when the equip-ment or structure is at rest as well as whenit is in operation. The distinction betweennatural and induced environmental factorscannot always be clearly discerned nor pre-cisely defined.

ENVIRONMENTAL FIELD TEST—A test


materiel is subjected to storage and func-tional testing in one or more specific en-vironments.

ENVIRONMENTAL LAPSE RATE — Therate of decrease of temperature with ele-vation. The concept may be applied toother atmospheric variables (e.g., lapserate of density) if these are specified. Theenvironmental lapse rate is determined bythe distribution of temperature in the ver-tical at a given time and place and shouldbe carefully distinguished from the Proc-ess lapse rate, which applies to an indi-vidual air parcel. (AMS) *

ENVIRONMENTAL OPERATING CONDI-TIONS — Those factors of the environ-ment which singly or in combination havea significant effect upon military opera-tions, and must, therefore, be consid@edin the design and testing of Army materiel.(AR)

ENVIRONMENTAL PROTECTION — Re-search and its application designed tomaintain or improve the degree of effec-tive performance of man and equipmentunder all types of environmental etress.

ENVIRONMENTAL RESEARCH — Thesystematic study and investigation of anyenvironmental factor or combination offactors for the purpose of discoveringbasic rules or principles governing theircause and behavior, extending knowledgeof their occurrence and distribution, orascertaining the relation between them andother aspects of the environment, both na-tural and induced. See also RESEARCHand APPLIED ENVIRONMENTAL RE-SEARCH.

ENVIRONMENTAL RESISTANCE FEA-TURES — The characteristics or the prop-erties of an item which protect the itemagainst the effects of an environmental ex-posure and which prevent internal condi-tions that might lead to deterioration.

ENVIRONMENTAL SUITABILITY OF A

e or program of tests in which an item of PRODUCT — The suitability of a product

51



to serve its intended purpose under pre-scribed environmental conditions.

ENVIRONMENTAL TEST — A test ofequipment, supplies, and techniques undera specific set of environmental conditionsin which each is intended to be used. Sucha test will normally be an integral part ofother tests, i.e., engineer design, engineer-ing, and service tests. (AR 705-15)+

EPHEMERAL LAKE—See PLAYA.

EQUATORIAL AIR — According to someauthors, the air of the doldrums or theequatorial trough, to be distinguishedsomewhat vaguely from the TROPICALAIR of the trade-wind zones, Tropical air“becomes” equatorial air when the formerenters the equatorial zone and stagnates.There is no significant distinction betweenthe physical properties of these two typesof air in the lower troposphere. (AMS)

EQUILIBRIUM VAPOR PRESSURE—Thevapor pressure of a system in which two ormore phases of a substance coexist in equi-librium. In meteorology the reference isto water substance unless otherwise spe-cified. If the system consists of moist airin equilibrium with a plane surface ofpure water. or ice, the more specializedsaturation vaporpressure is usually em-ployed, in which case the vapor pressureis a function of temperature only. (AMS) o

EQUILIBRIUM W.4TER — That water con-tent of a solid which wilt remain un-changed by further exposure to air of agiven humidity, temperature, and pres-sure.

ERG, n.— 1. Physics. The work performedby a force of one dyne acting through adistance of one centimeter. The erg is theunit of energy or work in the centimeter-gram-second system. (ND) 2. Geol. Anextensive area in a desert where the sur-face is loose or almost unconsolidated sand,usually forming high dunes. Sometimescalled a sand sea,

ERODE, v. — To wear away or remove the

land surface by wind, water, or otheragents. (SSS)

EROSION, n.— 1. GeoL The wearing awayof the. land surface by detachment andtransport of soil and rock materialsthrough the action of moving water, wind,or other geological agents. (YA) 2. Metat-/uvov. ,~truction of metal or other ma-terial by the abrasive action of liquid orgas. Usually accelerated by the presenceof solid particles of matter in suspensionand sometimes by CORROSION. ( ECS)

EROSION, ACCELERATED — Erosionmuch more rapid than normal, natural,geological erosion, primarily as a result ofthe influence of the activities of man or, insome cases, of animals. (SSS)

ERRATIC, n.— A rock fragment, usually oflarge size, that has been transported froma distant source, especially by the action ofglacial ice. (S&V)

ESCARPMENT, n.—A long CLIFF or steepslope facing in one general direction andcontinuing for a considerable distance. Es-carpments may be produced by faulting or ●by erosion. The abbreviated form “scarp”is usually limited to cliffs formed by fault-ing. (S&V)

ESKER, n.— Relatively long, narro~r, wind-ing ridges of mixed sand and gravel. Inlongitudinal profile their crests are seento be sinuous. They are considered to havebeen deposited by streams of meltwaterflowing through crevasses and tunnels instagnant ice sheets. (S&V)

ESTUARY, n.— The widened channel at themouth of a river, in which the influence ofthe tides is felt. The water in an estuaryis normally brackish.

EVAPORATION, n.—The process by whicha substance is changed from the liquid intothe vapor state, In hydrology, evaporationis vaporization that takes place at a tem-perature below the boiling point. (MH)

EVAPORATION PAN — A type of .4T-

52 ●


“a MOMETER; it is a pan used in the meas-urement of the evaporation of water intothe atmosphere. The U. S. Weather Bureauevawration pan (class-A pan) is a cyiin.drical container fabricated of galvanizediron or monel metal with a depth of teninches and a diameter of forty-eight inches.(AMS) ‘

EVAPORATION, TOTAL — The sum of wa-ter lost from a given land area during anyspecific time by transpiration from vege-tation and building of plant tissue; byevaporation from water surfaces, moistsoil, and snow; and by interception. It hasbeen variously termed evaporation, ewzp-or’ation from land areas, evapotranepiva-tion, total 10SS,water losses, a& flu off.(AMS)

EVAPORATIVITY, n.— Same as EVAP-ORATIVE POWER.

EVAPORATIVE POWER — A measure ofthe degree to which the weather or climateof a region is favorable to the process of

● evaporation. It is usually considered to bethe rate of evaporation, under existingatmospheric conditions, from a surface ofwater which is chemically pure and hasthe temperature of the lowest layer of theatmosphere ( (AMS ) *

EVAPORIMETER, n.— An instrument formeasuring the rate of evaporation of waterinto the atmosphere. (ND )

EVAPOTRANSPIRATION, n.— The com-bined processes by which water is trans-ferred from the earth’s surface to the at-mosphere; evaporation of liquid or solidwater plus transpiration from plants.(AMS) *

EVERGREEN, n.— Any of the variousneedled and broad-leaved trees, shrubs,and herbs which retain their green foliagethroughout the year, and which do.not shedthis foliage until the new leaves have de-veloped. (ADT) *

EXAGGERATION FACTOR — The factor

●by which a real-time environmental stress

53


level must be multiplied in order to simu-late a real-time service life by laboratorytest of short duration, (SVH)

EXCITATION—An external force (or otherinput) applied to a system that causfs thesystem to respond in some way. (SVH )

EXFOLIATION, n.— 1. Scaling off of asurface in flakes or layers. (ECS) 2. Geol.The breaking or SPALLING off of thinconcentric shells, scales, or lamellae fromrock surfaces. The action is due to changesin temperature, the action of frost, and,in the opinion of some observers, to ob-scure chemical effects. See SPALL (S&V)

EXPOSURE, n.— 1. State of being open tothe effects of a certain natural or simu-lated element or condition. Natural ezpo-sure refers to the subjection of a materialto normal *service conditions; acceleratedexposure refers to subjection to more strin-gent conditions. 2. In meteorology, thephysical location of an instrument.[AMS) * 3. The general surroundings ofa site, with special reference to its open-.nees to winds and sunshine. (AMS)

EXTERNAL EXPOSURE — Exposure toionizing radiations coming from a sourceoutside the body.

EXTINCTION, n.— The ATTENUATIONof light; that is, the reduction in lLLUMl-NANCE of a parallel beam of light as thelight passes through a medium whereinABSORPTION and SCATTERING occur.(AMS)

EXTRA-TERRESTRIAL RADIATION—1.Radiation (electromagnetic and chargedparticles) originating in space beyond theearth’s atmosphere, e.g. solar radiationand primary coemic rays. 2. .kfeteorol. Thesolar electromagnetic radiation received atthe outer limits of the atmosphere. (AMS) *

EXTREME, n.- In climatology, the high-est and, in some cases, the lowest value ofa climatic element observed during a givenperiod or during a given month or seasonof that period. If this is the whole period



for which observations are available, it isthe absoluts eztreme. (AMS)

EYE OF THE STORM (or EYE) —MeteoroLThe roughly circular area of compara-tively light winds and fair weather foundat the center of a severe tropical cyclone.The winda are generally ten knots or Iess;no rain occurs; sometimes blue sky mayIM seen. Eye diamsters vary from fourto more than forty miles; common magrri-tudes seem to be twelve to twenty-fivemiles. (AMS) *

F

F — Abbreviation for FAHRENHEIT TEM-PERATURE SCALE.

FADING, n.— The resultant change or lossin the original color of protective coatingsor materials due to exposure to solar radiantenergy, heat, chemicals, chemical fumes, orcombinations of these.

FAILURE—Any operational or performancedegradation, or any irreversible material orstructural change, when examined in ac-cordance with specific failure criteria.

FALLBACK, n.— That part of the materialcarried into the air by a surface or subsur-face atomic explosion that ultimately dropsback to the earth or water at the site of theexplosion. (AFD) See FALLOUT.

FALLING TIDE — The portion of the tidecycle between high water and the followinglow water. (AMS)

FALLOUT, n.— The process of precipitationto earth of radioactive particulate matterfrom a nuclear cloud; also applied to theparticulate matter itself. (JD)

FALLOUT CONTOURS — Lines joiningpoints which have the same radiation in-tensity that define a fallout pattern, repre-sented in terms of roentgens per hour. (JD)

FALLOIJT PATTERN — The distribution offallout as portrayed by fallout contours.(JD)

FALSE HORIZON — A line resembling thevisible horizon but above or below it. (AF)

FAN, n. — See ALLUVIAL FAN,

FAST ICE — Any type of sea, river, or lakeice attached to the shore (ice foot, ice shelf),beached (short ice), stranded in shallowwater, or frozen to the bottom of shallowwaters (ANCHOR ICE) . (AJfS)

FATIGUE, n. — A reaction which takes placein material under repeated cyclic stressing,resulting in a tendency for that material tofail below its static ultimate strength.

FATIGUE LIFE — The number cycles ofstress or stress reversals that can be sus-tained prior to failure for a stated test con-dition.

FATIGUE LIMIT — The maximum stressbelow which a material can presumably en-dure an infi~ite number of stress cycles. Ifthe stress is not completely reversed, thevalue of the mean stress, the minimumstress, or the stress ratio should be stated.The fatigue limit of a material is frequentlyreferred to as its endurance limit.

FAULT, n.— A fracture in the earth’s crust,accompanied by a displacement of one sidewith respect to the other in a direction par-allel to the fracture. (GS)

FAULTING, n. — Movement along a fault.Faulting is the most usual cause of earth-quakes.

FAULT-LINE SCAFiP — A scarp that is notthe exact original face created by faultingbut has been modified by ero,sion from theoriginal scarp. It may have the same reliefas the original scarp but is usually behindit and much more irregular in outline.(s&v)

FAULT-SCARP — A scarp which owes itsrelief directly to the movement along afault, even though erosion may have great-ly scarred the initial topography. (S&V)

FAUNA, n. — 1. The animals of a region,

54


m zone, or environment. (ADT) 2. A list, cat-alogue, or systematic report with keys ordescriptions pertaining to the animals of aspwific region, hence arctic fauna, alpinefauna. (ADT)

FETCH, n.— 1. The area in which oceanwaves are generated by the wind. It ie gen-erally delineated by coast lines, fronts, orareas of wind curvature or divergence.(AMS) 2. The length of the fetch area,measured in the direction of the wind.(AMS)

FIELD MOISTURE CAPACITY — The per-centage of water remaining in a soil 2 or 3days after having been saturated and afterfree drainage has practically ceased. Thepercentage may be expressed on the baais ofweight or volume. (SSS)

FIELD MOISTURE DEFICIENCY — Thequantity of water, which would be requiredto restore the soil moisture to field moisturecapacity. (MH )

FINE-GRAINED SOIL — A soil of whichmore than 50 ~. of the grains, by weight,will pass a No, 200 sieve (smaller than0.074 mm in diameter). (TM 3-240)

FINISH, n.— 1. The quality of a surface asdetermined by color, brightness, texture,and general surface appearance. 2. Any sur-face treatment accomplished for the pur-poses of protecting equipment against en-vironmental depreciation, enhancing ap.pearances, for camouflage purposes, or foridentification.

FIORD (or FJORD), n.— A deep, narrow,and steep-walled inlet of the sea formed inmost instances by intense glacial erosion ofa valley. Some fiords may have been invadedby ocean water after glaciation and owingto general subsidence of the land, but mostare the direct result of erosion by tonguesof ice that actually entered the ocean andmoved along the bottom. (S&V )

FIREBALL, n.— The luminous sphere of hotgases which forms a few millionths of a sec-ond after detonation of a nuclear weapon


and immediately starta expanding and cool-ing. (JD)

FIRN, n. — 1. In the International SnowClassification, old snow which has lastedthrough at least one summer; the flakeshave changed to grains of spherieal ahapewhich may or may not be bonded together.Fim may later become glacial ice. (ADT)2. An accumulation area. (ADT) Alsocalled NtVk in both senses. See FIRNLINE.

FIRN LINE — The highest level to which thefresh snow on a glacier’s surface retreabduring the melting season. The line separat-ing the accumulation area from the abla-tion area. (See FIRN) (MH)

FIRST BOTTOM — The normal tlood plainof a stream, aubjat to frequent or occa-sional flooding. (YA)

FIRST LIGHT — The beginning of morningnautical twilight, i.e., when the center ofthe morning sun is 12” below the horizon.(JD)

FIRST-ORDER CLIMATOLOGICAL STA-TION – As defined by the World Meteor@logical Organization (1956), a meteorologi-cal station at which autogrsphic records orhourly readirrgs of atmospheric pressure,temperate, humidity, wind, sunshine, andprecipitation are made, together withobservations at fixed hours of the amountand form of clouds and notes on theweather. (AMS)

FISHTAIL WIND — Wind that is constantlychanging direction back and forth. (AD)

FIXED ECHO — A radar echo that is causedby reflection from a fixed object such as aterrain form or building visible to the radarset. (AD)

FLAKING, n.— A protective coating failureassociated with paints, varnishes, lacquers,and allied formulations. It is characterizedby actual detachment of pieces of the coat-ing either from its substratum or ‘frompaint previously applied. Flakkrg is some.times referred to as scaling and is generally

55


MIL-STD-11652S MARCH 1968

preceded by checking or cracking. Flakingis attributed to loss of adhesion of the coat-ing.

FLASH FLOOD — A flood that rises and fallsquite rapidly with little or no advancewarning, usually as the result of intenserainfall over a relatively small area. Otherpossible causes are ice jams, dam failure,etc. (AMS)

FLOATING ICE (or DRIFT ICE) —Anysea ice that has drifted from its place oforigin. The term is used in a wide sense toinclude any area of sea ice, other than fastice, no matter what form it takes or howdisposed. (NOO)

FLOCCULATE, v.— To aggregate or clumptogether individual tiny soil particles, es-pecially fine clay, into s;mall groups or gran-ules. The opposite of defloccukzte, or di-s-pm-se. (YA)

FLOE, n.— A single piece of sea ice, otherthan fast ice, large or small, described ifpossible as “light” or “heavy” according tothickness. A vast floe is over 10 kilometers(5.4 nautical miles) across; a big floe is1 to 10 kilometers (3,281 feet to 5.4 nauti-cal miles) across; a medium floe is 200 to1,000 meters (656 to 3,281 feet) across; asmall floe is 10 to 200 meters (32.8 to 656feet) across. (NOO)”

FLOOD, n.— 1. An overflow or inundationthat comes from a river or other body ofwater and causes or threatens damage.

(MH) 2. Any relatively high streamflowovertopping the natural or artificial banksin any reach of a stream. (MH) 3. A rela-tively high flow as measured by either gageheight or discharge quantity. (MH)

FLOOD-FREQUENCY CURVE—l. A graphshowing the number of times per year onthe average, plotted as abscissa, that floodsof magnitude, indicated by the ordinate, areequaled or exceeded. (.MH) ‘2. A similargraph but with recurrence intervals offloods plotted as abscissa. (MH )

FLOOD PLAIN — 1. A strip of relatively

smooth land bordering a stream, built ofsediment carried by the stream and droppedin the slack water beyond the influence ofthe swiftest current. It is called a livingffood pbin if it is overflowed in times ofhighwater; but a fossil ffood pktin if it isbeyond the reach of the highest flood. (MH)2. The lowland that borders a river, usua!lydry but subject to flooding. (MH) 3. Thatland outside of a stream channel describedby the perimeter of the maximum probableflood. (MH)

FLOOD PLAIN, FIRST BOTTOM — SeeFIRST BOTTOM.

FLOOD STAGE — 1. The gage height of thelowest bank of the reach in which the gageis situated. The term “lowest bank” is, how-ever, not to be taken to mean an unusuallylow place or break in the natural bankthrough which the water inundates an un-important and small area. ( NfH) 2. Thestage at which ovehlow of the naturalbanks of a stream begins to cause damagein the reach in which the elevation is meas-ured. (MH)

FLOOD WAVE — A distinct rise in stage cul-minating in a crest and followed by reces-sion to lower stnges. (MH)

FLOOD ZONE—The land bordering a streamwhich is subject to floods of about equalfrequency; for example, a strip of the floodplain subject to flooding more often thanonce but not as frequently as twice in acentury. (kIII)

FLORA, n.— 1. The veget~tion of a region,zon,e, or environment. (ADT) 2. A list, cat-alogue, or systematic report with keys ordescriptions pertaining to the plants of aspecific region, hence alp”nc floro, bog flora.(ADT)

FLOTATION, n.- 1. The capacity of a vehi-cle, gun, or trailer to negotiate water obsta-cles without being in contact with the bot-tom. ( JD) 2. The capacity of a vehicle tonegotiate soft, unfavorable terrain such asmud, sand, or snoiv. (JD)

S6


FLOW-DURATION CURVE —A cumulativefrequency curve that shows the percentageof time that specified discharges are equaledor exceeded. (MH )

FLURRY, n.— A brief shower of snow ac-companied by a gust of wind, or a sudden,brief wind squall. (ND)

FLYING LEVELS — A line of levels in sur-veying, to determine approximate eleva-tions to hundredths or tenths of a foot.(AD)

FOCUS, n.— In seismology, the source of agiven set of elastic waves. The true centerof an EARTHQUAKE, within which thestrain energy is first conl!erted to elasticwave energy.

FOEHN (or FOHN), n.— A warm, dry windon the lee side of a mountain range, thewarmth and dryness of the air being due toadiabatic compression upon descending themountain slopes. The foehn is characteris-tic of nearly all mountnin areas. It is as-sociated with cyclonic-scale motions, beingproduced only when the circulation is suf-ficiently strong and deep to force air com-

1pletely across a major mountain range in ashoti period of time. In different mountainregions the foehn has a variety of names, asthe CHINOOK of the Rocky Mountains.(AMS)”

FOG, n.— A hydrometer consisting of a vis-ible aggregate of minute water dropletssuspended in the atmosphere near theearth’s surface. According to internationaldefinition, fog reduces visibility below onekilometer (0.62 mile). Fog differs fromcloud only in that tbe base of fog is at theearth’s surface while clouds are above thesurface. When composed of ice crystals, itis termed ice too. (AMS) * See also AD-VECTION FO”G,”GROUND FOG, RADI~-TION FOG.

FOGGING, n,— The application of chemicalcompound in the form of vapor, to interiorsurfaces or relatively inaccessible surfaces.(AD)


FOOTHILL — One of the lower subsidiaryhills at the foot of a mountain or of higherhills. Commonly used in the plural. (GS)

FORE, n.- A nongrasslike herbaceoua plant.(SAF) “

FORCE FACTOR — In an electromechanicalTRANSDUCER, (a) the complex quotientof the force required to block the mechani-cal system divided by the correspondingcurrent in the electrical system; (b) thecomplex quotient of the resulting open cir-cuit voltage in the electrical system dividedby the velocity in the mechanical system.As an alternative, current may be replacedby charge in (a) and velocity by displace-ment in (b). (SVH)

FORCED OSCILLATION (FORCED VI-BRATION) — The steady-state oscillationof a system caused by a periodic excitation.(Transient oscillations are not considered.)(ISO)*

FORD, n.— 1. A place where a stream orother water is commonly passed by man orbeast by wading. (GS) 2. A place where aroad or trail crosses a body of water with-out a bridge or ferry. (GS)

FORDABILITY — See DEEP FORDING,SHALLOW FORDING.

FOREST, MIXED — A forest composed oftrees of two or more species. In practice,usually a forest in which at least 20 per centare trees of other than the principal species.(SAF)

FOREST, PARK — A forest in which thetrees stand apart from one another or indetached groups; a very open forest inwhich usually the characteristic forest flooris replaced by grasses. (SAF )

FOREST, PURE — A forest composed prin-cipally of trees of one species, usually tothe extent of 80 percent or more by numberbut in special cases a percent of basal areaor volume. (SAF)

FOREST, SECOND-GROWTH — 1. Forestgrowth which occurs after removal of the

57


MlL-STD-l I ba25 MARCH 1968

old stand by cutting, fire, or other cause.2, In lumberman’s parlance, the smallertrees left after lumbering or the trees avail-able for a second logging.

FOREST TYPE — A descriptive term usedto group stands of similar character. as re-gards composition and development due tocertain ecological factors, by which theymay be differentiated from other groups ofstands. The term suggests repetition of thesame character under similar conditions: Atype is temporwy if its character is due topassing influences such as logging or fire;permanent if no appreciable change is ex-pected and the character is due to ecologicalfactors alone; clirnaz if it is the ultimatestage of a succession of tempwary types.A cover type is a forest type now occupyingthe ground, no implication being conveyedas to whether it is temporary or permanent.(SAF)

FORMATION, n.— In botany, one or moreplant communities exhibiting a definitestructure and physiognomy; a structural orphysiogonomic unit of vegetation; e.g., agraminoid marsh, a deciduous broadleafforest.

FORWARD SCATTER — The scattering ofradiant energy into the hemisphere of spacebounded by a plane normal to the directionof the incident radiation and lying on theside toward which the incident radiationwas advancing; the opposite of BACK-WARD SCATTER. (AMS) *

FORWARD SLOPE — Any slope which de-scends towards the enemy. (J D)

FRACTION OF CRITICAL DAMPING —The ratio of the actual damping coefficientof a system with viscous damping to thecritical damping coefficient. (SVH)

FRAGILITY — The capability of a piece ofequipment to withstand shock and vibra-tion, expressed as a maximum permissibleacceleration. (SVH )

FRAZIL — Discoid and crystalline ice which

forms in supercooled water without coagu-lating into an ice sheet. It is the product ofa critical air temperature and water tem-perature condition with the latter possiblydominated by mdiational heat losses. For-mation takes place in the more or less quie-scent or tranquil flowing reaches of astream where the critical supercooling maytake place and prevail for sufficient time forthe individual particle to form rather thanfor an ice sheet to grow outward from ashore. When the ice reaches a rapids orother area of excessive turbulence it agglo-merates and becomes very noticeable. It alsoforms in the sea (where it is called LOLLYICE). It may accumulate as ANCHORICE on rocks or other obstructions on thebottom of a river.

FREE, adj. — The condition of the substancewithin a mixture when it is not chemicallycombined with the other components of themixture. For example, iron oxide in soilsmay be by itself as free iron oxide, or itmay be combined with other elements in amineral. (YA) *

FREE AIR — 1. That portion of the atmo-sphere undisturbed by objects on the sur-face of the earth, as by mountains or build-ings. (AFD) 2. Meteorology. That portionof the earth’s atmosphere above the plane-tary boundary layer, in which the effect ofthe earth’s surf ace friction on the air mo-tion is negligible, and in which the air isusually treated as an ideal fluid; alsocalled free atmosphere. (AMS) * 3. Aerody-namics. Nonturbulent air; air undisturbedby a moving body, as by an airfoil. (AFD)4. In contexts regarding atomic explosions,air sufficiently remote from surfaces or ob-jects that an explosive effwt, as blast, is notmodified by reflected shock or scattering ob-jects. (AFD)

FREE-AIR ANO}lALY — The difference be-tween observed gravity and theoreticalgravity which has been computed for lati-tude and corrected for elevation of the sta-tion above or below the geoid, by applica-tion of the normal rate of change of gravity

38

●


.0

for change of elevation, as in free-air. (JD)FREE AIR OVERPRESSURE – The prea.cure,

created by arr explosion which is in excessof atmospheric pressure. (AD)

FREE FIELD — A wave or potential field ina homogeneous, isotropic medium free fromboundaries. In practice, it is a field in whichthe effects of the boundaries are negligibleover the region of interest. The actual pres.sure impinging on an object (e.g., electro-acoustic transducer) placed in an otherwisefree sound field will differ from the pressurewhich would exist at the point with the ob.ject removed, unlea.qthe acoustic impedanceof the object matches the acoustic imped-ance of the medium.

FREE OSCILLATION (or FREE VIBRA-TION ) — Oscillation that occurs after thedisturbance or original cause of the osciRa-tion is no longer present.

FREEZING, n.— The change from a liquidto a solid state, usually by the abstractionof heat. The opposite is MELTING. (ND)

FREEZING INDEX — As used by the U.S.Army Corps of Engineers, the number ofDEGREE DAYS (above and below 32” F.)between the highest and lowest points onthe cumulative degree-days time curve forone freezing season. (AMS)

FREEZING POINT — The temperature atwhich a liquid solidifies under any given setof conditions. It may or may not be the sameaa the MELTING POINT or the more rig-idly defined true freezing point or (for wa.ter) ice point. (AMS) ●

FREQUENCY — 1. In general, the numberof times a designated phenomenon occurswithin a given period. It may be expressedin units of radians per second or of osciRa-tions (cycles) per second (see HERTZ).2. Climatology. The number of times a ales.Ignated phenomenon occurs within a givenperiod. It may be expressed as occurrencefrequency (e.g., number of rainy days permonth, number of hours of sunshine perweek, etc. ) or percent frequency (percentof observations). (AMS) *

FREQUENCY, FUNDAMENTAL — 1. Thereciprocal of the fundamental period. (1S0)


2. Tbe lowest natural frequency. The nor-mal mode of vibration associated with thisfrequency is known as the frmdamentalmode. (1S0)

FREQUENCY, INFARED —The range ofinvisible radiation frequencies, which ad-joins the visible red spectrum and extendsto microwave radio frequencies.

FREQUENCY, NATURAL — The rate atwhich a freely vibrating body oscillates.

FREQUENCY, RADIO — Any frequenoy atwhich electromagnetic radiation of energyis useful for communication, usually slatedin terms of kilocycles or megacycles persecond. Radio frequencies are usuallyclassed aa very low, below 30 kilocycles persecond; low, 30-300 kilocycles per second;medium, 300-3,000 kilocycle per second;high 3-30 megacycles per second; very high,30-300 megacycles per second; ultra high,300-3,000 megacycles per second; superhigh, 3,000-30,000 megacycles per second;and extremely high, 30,000-300,000 mega-cycles per second. (ND) *

FREQUENCY, RESONANT — The frequen-cy of EXCITATION at which a body orsystem in forced vibration hae its maximumresponse (see RESONANCE). (SVH) ●

FREQUENCY RESPONSE — The capabil-ity of test or measuring equipment to re-spond to the peak values of an external os-cillatory stimulus.

FRESNEL ZONE — Used to describe theamount of clearance (or obstruction) en-countered by an electromagnetic wave. Thenth fresnel zone may be defined as a cylin-drical surface or revolution having the ili-rect path se its axis, and possessing a con-tour such that the distance from the trans-mitting antenna to a point on the surface,plus tbe distance from this point to the re-ceiving antenna in n/2 wavelengths greaterthan the direct path between transmitterand receiver.

FRETTING CORROSION — Corrosion atthe interface Ir+tween two contacting sur-

S9



faces accelerated by relative vibration be-tween them of amplitude high enough toproduce slip. (ECS)

FRIABLE, adj. — A consistency term per-taining to the ease of crumbling of soils.(sss)

FRICTION, n. — The rubbing together. oftwo substances or bodies in contact witheach other, of a body in contact with a gasor tluid, etc. ; the resistance to relative mo-tion caused by this contact. (AFD)

Some specific types of friction are: ~1. Boundary Friction — Friction occurring

when the rubbing surfaces are separated fromeach other by a very thin film of lubricant orreduced through use.

2. DPU Friction — Friction b+tween solidsurfaces without benefit of lubricant.

3. Fluid Frictio-n — Friction occurringwhen two bearing surfaces are covered with alubricating fluid.

4. Rolling Friction — Friction due to theindentation of the surfaces in rolling contact.It is frequently substituted for sliding fric-tion,but is less than sliding friction. Exam-ple :’the use of ballbearings.

5. Skin Friction — (1) Aerodynamics. Thefriction of the air against the outside of amoving aircraft, rocket, or the like, especiallyat high speeds; the drag of resistance causedby this friction. (2) Hydrodwzamics. Similar-ly, the friction of water against a ship’s hull.

6. .Srtrfacs Friction — The friction of a li-quid flowing through pipes, caused by rate offlow, pressure, liquid viscosity, etc.

FRICTION LAYER —1. Meteorology. Thelower layer of the troposphere, in whichthe friction of the air against the earth’ssurface affects the movement of the air. Thefriction layer is considered to bt. anywherefrom 1,500 to 3,000 feet thick. (AFD)Above this layer lies the free atmosphere,

FRIGORIMETER, n.— An instrument tomeasure the physiological cooling power inmilli-celories per square centimeter andminute. It consists of a blackened copper

sphere, diameter 7.5 cm, the surface ofwhich is maintained electrically at 36.5° C(97.7° F) against the heat losses due’ to allmeteorological conditions of the ambientair. The temperature 36.5° C corresponds tothe constant deep body temperature of man.(An older model was set at 33° C) (AMS) *

FRINGING REEF— A coral reef that isclosely attached to the shore. There is nolagoon or opm water between the reef andthe land upon which it is attached. It is usu-ally built upon a shallow platform extend-ing outward from the shoreline and may belaid bare at time of very low tide. (S&V)

FRONT, n. — In meteorology, generally, theinterface or transition zone between twoAIR MASSES of different density. Sincethe temperature distribution is the most im-portant regulator of atmospheric density, afront almost invariably separates airmasses of different temperature. Alongwith the basic density criterion and thecommon temperature criterion, many otherfeatures may distinguish a front, such as apressure trough, a change in wind direction,a moisture discontinuity, and certain char-acteristic cloud and precipitation forms.(AMS) *

FROST, n.— 1. A feathery deposit of minuteice crystals or grains upon a surface or ob-ject, formed directly from vapor in the air.(AFD) 2. The process by which such icecrystals are formed. (.\FD) 3. Any tenl-perature at which frost forms. Frost oftenforms when the close lying air is above 32°F, especially in calm, clear weather whenradiation or evaporation reduces a surfacetemperature to a point of freezing or below.(AFD)

FROST ACTION — In general, cycles offreezing and thawing of water contained innatural or man-made materials. This is es-peciall y applied to the disruptive effects ofthis action. Ir. geolo~, two basic types offrost action are described: (a) CONGELI-FRACTION, the shattering or splitting ofrock material; and (b) CONGELITURBA-

60


TION, the churning, heaving, and thrust-ing of soil material. (AMS)

FROST HEAVE — The upwards or sidewaysmovement of surface soils, rocks, and vege-tation through the expansion of freezingsubsurface soil and gravel. Also called frostthrustingand frost lifting. (ADT) *

FROST LINE — The maximum depth offrozen ground during the winter. The termmay refer to an individual winter, to theaverage over a number of years, or to thegreateet depth recorded since observationsbegan. The frost line varies with the natureof the soil and the protection afforded byvegetal ground cover and snow cover, aswell aa with the amount of seasonal cooling.(AMS)

FROST WEATHERING — The mechanicaldisintegration of earth materials broughtabout by frost action.

FROZEN MUSKEG SURFACE — A frozenmixture of decayed vegetable matter andsilt-like material which resembles rough,hard ground,

FUMES, n.— Fine particles (0.2 to 1 micronin diameter) generated by condensationfrom the gaseous state, generally aftervolatization from molten metals, etc., andoften accompanied by a chemical reactionsuch as oxidation. Fumes flocculate andsometimes coalesce.

FUNGI (PI. of FUNGUS), n.-Simple plantorganisms lacking chlorophyll which en-ables higher planta and algae to manufac-ture their own food. Because of this in-ability to synthesize food, fungi are whollydependent on organic materials for theirnutrient supply. This dependence rendersfungi capable of degrading almost all ma-terials of an organic origin.

FUNGICIDE, n.— An agent that destroysfungi.

FUSION, n.- 1. The phase transition of asubstance passing from the solid to theliquid state; melting. Additional heat at


the melting point is required to fuse anysubstance. This quantity of heat is calledthe latent heat of fusion. (AMS) * 2. Innuclear technology, the transformation ofnuclei by combining two light nuclei toform a heavier nucleus.

G

g, n,- The acceleration produced by theforce of gravity, which varies with thelatitude and elevation of the point of ob-servation, By international agreement, thevalue 980.665 cm/see: -386.089 in/see? -32.1740 ft/sec2 (baaed on the NationalBureau of Standards redefinition of theinch as being exactly equal to 2.54 cm) has

‘been chosen as the standard accelerationdue to gravity. (ASA) *

GAGE, n.— An instrument for measuringthe size or state of anything. (ND)

GAGE, v.t. — To determine the size or stateof anything. (ND)

GAGE HEIGHT — The water-surface eleva-tion referred to some arbitrary gage datum.Gage height ia often used interchangeablywith the more general term stage althoughgage height is more appropriate when usedwith a reading on a gage. (MH)

GAGE, STRAIN — A device for measuring“strain” which is the deformation pro-duced in a solid as a result of STRESS.(AF)*

GAGING STATION — A particular site ona stream, canal, lake, or reservoir wheresystematic observations of GAGE HEIGHTor discharge are obtained. (MH )

GALE, n.— 1. In general, and in popularuse, an unusually strong wind. (AMS)2. In storm-warning terminology: moder-ate gale, 28 to 33 knots; fresh gale, 34”to40 knots; strong gale, 41 to 4’7 knots; andwhole gale, 48 to 55 knots. (AMS) *

GALLING, n.— The localized mutual seizureof two metal surfaces during sliding fric-

61



tion accompanied by the removal of metalparticles from one or both surfaces.

GALVANOME7ER, n.— An instrument formeasuring the magnitude of a small elec-tric current or for detecting the presenceor direction of such a current by means ofmotion of an indicator in a magnetic field.(ND)

GAMMA RAY - Electromagnetic radiationof extremely short wavelengths, ‘emittedby nuclei. The wavelengths of the highestenergy gamma rays are shorter than x-rays, but there is an overlapping wave-length region where the only distinctionis the mode of origin; i.e. the gamma raysare produced by nuclear transitions where-as the x-rays are produced by atomic proc-esses. Gamma rays, produced in the atmos-phere by interactions of cosmic rays withthe nuclei of air molecules, are of some im-portance to atmospheric electricity becausethey contribute to the ionization of theatmosphere.

GAP, n. — 1. Geot. Any deep notch, ravine, oropening between hills or in a ridge ormountain chain. (GS) 2. i?k?ctn”e gap isthe distance separating two electrodes be-tween which a spark or arc is caused topass. 3. Magnetic gap is the distance acrossan air gap separating two parts of a mag-netic circuit.

GAS THERMOMETER — A thermometerwhich utilizes the thermal properties ofgas. There are two forms’ of this instru-ment: (a) a type in which the gas is keptat a constant voIume, and pressure is thethermometric property; and (b) a’ type inwhich the gas is kept at constant pressure,and volume is the thermometric property.The gas thermometer is the most accurateof all thermometers and is used as thestandard instrument for measurement oftemperature. (AMS)

GENERATING AREA — See FETCH.

GENESIS, SOIL — Peddogy. The mode oforigin of the soil, with special reference

to the processes responsible for the de-velopment of the solum, or true soil, fromthe unconsolidated parent material. (Y-A)

GEODESY — The investigation of any sci-entific question concerned with the shapeand dimensions of the earth. The term isoften used to include both the sciencewhich must depend upon determinations ofthe figure and size of the earth from directmeasurements made on its surface ( trian-gulation, leveling, astronomic, and gravitydeterminations), and the art which utilizesthe scientific determinations in a practicalway. (NOO)

GEOGRAPHIC COORDINATES — Latitudeand longitude; north south and east westlines whose intersections are used to lo-cate physical points on a map. The originfor latitude is the equator and increases

, north and south to 90 degrees. Origin for(

longitude is the meridian or great circlepassing through Greenwich, England,called the “Prime Meridian” and increas-ing east and west to 180 degrees. (AD)

GEODETIC CONTROL — Horizontal posi- mtion of points on the earth’s surface in thecomputation of which the curvature hasbeen taken into account. (AD)

GEOMAGNETISM — 1. The magnetic ph-nomena, collectively considered, exhibitedby the earth and its atmosphere. 2. Thestudy of the magnetic field of the earth.(AMS)

G E O M A G NET I C ELECTROKINETO-GRAPH — A device for measurement ofthe lateral component of the speed of anocean current, by means of two pairs ofelectrodes towed astern, and suitable reg-istering apparatus. (ND)

GEOPHYSICS — Broadly, the physics of theearth, including the fields of METEOR-OLOGY, HYDROLOGY, OCEANOGRA-PHY, SEISMOLOGY, VOLCANOLOGY,GEOMAGNETISM, and GEODOSY. Inthe more popular and practical sense, theterm implies the application of electrical,

●62 —


“e thetnral, magnetic, gravimetric, and seis-mic methods to the exploration for petrol-eum, metals, and underground supplies ofwater. (S&V)

GEOPOTENTIAL, n. – The potential energyof a unit mass relative to sea level, numeri-cally equal to the work that would be donein lifting the unit mass from sea level tothe height at which the mass is located;commonly expressed in terms of dynamicheight or geopotential height. (AMS) *

GEYSER, n. - A special type of hot springthat throws forth intermittent jets of hotwater and steam. The action results fromthe contact of ground water and rock orvapor hot enough to generate steam undercond~tions that prevent continuous circu-lation. (S&V)

GILGAI, n.— The microrelief of soils pro-duced by expansion and contraction withchanges in moisture. Found in soils thatcontain large amounta of clay which swells

o

and shrinks considerably with wetting anddrying. Usually a succession of microbasinsand microknolls in nearly level areas or ofmicrovalleys and microridges parallel tothe direction of the slope. (SSS)

GIRDLE, v.t. — To encircle the stem of aliving tree with cuts that completely severbark and cambium and often are carriedwell into the outer sapwood, for the pur-pose of killing the tree by preventing pas-sage of nutrients.

GLACIAL, adj. — 1. Pertaining to the pres-ence, size, composition, or activities of ex.tensive masses ‘of land ice. (ADT) 2. Per-taining to alterations or distinctive fea-tures of terrain resulting from the actionsof glaciers. (ADT)

GLACIAL DRIFT — All rock material intransport by glacier ice, all deposits madeby glacier ice, and all deposits predomi-nantly of glacial origin made in the sea orin bodies of glacial meltwater. whetherrafted in iceb~rgs or transported in the

●water itself. It includes till, stratified drift,

62


and scattered rock fragments, (S&V)

GLACIATION, n, — 1. The alteration of anypart of the earth’s surface, either by ero-sion or deposition, as a result of glacierice passing over it; the erosive action ofglacier ice. (ADT) 2. Any of several per-iods of geologic time during which glacierswere more extensive than at present,(ADT) 3. The geographic distribution ofglaciers. (ADT) 4. The inundation of landby ice. Aleo called glacietizution. (ADT)5. The process by which glaciers accumu-late, move, and recede. (ADT)

GLACIER, n.— A body of ice (usually withsome n6v6) consisting of recrystallizedsnow, lying wholly or largely on land, andshowing evidence of present or formerflow under the influence of gravity.(s&v) ●

GLACIER ICEBERG — An iceberg derivedfrom a glacier aa distinguished from tabu-lar icebergs derived from shelf ice. (NOO)It ia usually much smaller than a tabulariceberg and is bluish or greenish in color,with little or no anow covering. It oftencontains many crevasses. (ND )

GLACIOFLUVIAL, ati. — Pertaining to astream or streams formed by the melt-water of a glacier or glaciera, or to de-posits made by such streams.

GLARE, n.—Any hindrance to vision causedby scattering or reflection of light into anobserver’s line of sight. (AMS) *

GLAZE, n.—A coating of ice, generally clearand smooth but usually containing someair pockets, formed on exposed objects bythe freezing of a film of supercooled waterdeposited by rain, drizzle, fog, or possiblycondensed from supercooled water vapor.Glaze is denser, harder and more transpar-ent than either RIME or HOARFROST.Its density may be as high as 0.8 or 0.9 gmper ems. Factors which favor glaze forma-tion are large drop size, rapid accretion,



slight supercooling, and slow dissipationof heat of fusion. (AMS) *

GLEIZATION, n.—Pedology. A general termfor all the pr.xess of soil formation lead-ing to the development, under the influenceof excessive moistening, of a glei (gley )horizon in the lower part of the solum. Asoil horizon in which the material ordinari-ly is”bluish gray or blue gray, more or lesssticky, compact, and often structureless, iscalled a glei hom”zon and is developed un-der the influence of exce~ive moistening,( s&v)

GLEY SOIL — Pedology, A soil horizon inwhich waterlogging and lack of oxygenhave caused the material to be a neutralgray in color, The term “gleyed” is applied,as in “moderately gleyed soil,” to soil hori-zons with yellow and gray mottling causedby intermittent waterlogging. (YA)

GORGE, n. — A canyon ;,a rugged and deepravine or gulch. (GS)

GRABEN, n.— A block, generally long com-pared to its width, that has been down-thrown along faults relative to the rockson either side. Compare HORST.

GRADATION, n.— Soil Mechanics. The dis-tribution and size of grains in a soil. It isdetermined by gradation analysis of soils,or passing the soil through a series ofscreens of increasing fineness. The resultis usually presented in the form of a cumu-lative grain-size curve in which particlesizes are plotted to a logarithmic scale withrespwt to percentage retained (or pass-ing), by weight of the total sample, plot-ted td a linear scale. (BR)

GRADE, n.— 1. Engineering. The rate ofascent or descent; deviation from a levelsurface to an inclined plane; stated: ( 1)as so many feet per mile, (2) as one footrise or fall in so many of horizontal dis-tmrce, (3) as so much in a hundred feet,or (4) as a percentage of horizontal dis-tance; as a grade of twenty feet per mile,or 1 in 264, or a 10 percent grade. (S&V) *

2. Geomorph. The continuous curve ofdescent of a stream floor which every-where is just steep enough to serve theneed of the current for its flow and thetransportation of its sediment bad. It iacommonly said that a river is at gradewhen its active downcutting ceases.(s&v) “

GRADEABILITY — Capability of a vehicleto negotiate a slope, either ascending ordescending, measured in percent (not indegrees). (AD)

GRADIENT, n.— 1. Slope expressed as afraction in which the vertical distance isthe numerator and the horizontal distanceis the denominator. (AD) 2. Rate ofchange of temperature or pressure in agiven direction; mathematical expressiongiving the direction and amount of themost rapid rate of decrease of temperatureor pressure. (AD) 3. Meteorol. The spacerate of decrease of a function. The a.scend-ent is the negative of the gradient. (AMS) *

GRAM-RAD, n.— A unit of total energy ab-sorbed from ionizing radiation. It is theproduct of the mass of the object irradi-ated and the energy absorbed per unitmass. As,, adopted by the InternationalCommission on Radiological Units (ICRU),1 gram-rad = 100 ERGS.

GRANULE, n.— 1. A little grain; a smallparticle. (S&V) 2. In the Wentworth sys-tem of size classification, a granule is aparticle 2 to 4 mm in diameter. (S&V)

GRAVEL, n.— Loose or unconsolidatedcoarse, granular material, larger than sandgrains, resulting from reduction of reck bynatural or artificial means. Sizes rangefrom 3/16 inch (No. 4 sieve) to 3 inchesin diameter. Coarse gravel ranges from 3inches to 3/4 inch, while fine gravel rangesfrom 3/4 inch to 3/16 inch. (BR)

GRAVITY, n.-– 1. The gravitational force,as modified by centrifugal force due torotation, exerted by the earth on bodiesat or near its surface, resulting in their

64


having weight. (ND) 2. A unit of acceler-ation equal to the acceleration resultingfrom the average force of gravity at theearth’s surface. By international agree-ment this unit is equal to 9.80665 metersper second per second. (Gravity is abbre-viated.) (ND)*

GRAVITY ANOMALIES — Deviations be-tween theoretical gravity and actual gravi-ty due to local topographic and geologicconditions, such as the existence of moun-tains, valleys, oceans, or abnormally highor low density of the materials near theplace of measurement. (AF)

GRAVITY, SPECIFIC — The ratio of theweight of a substance to that of an equalvolume of some other substance at thesame or a standard temperature. The usualstandard for liquids and solids is chemi-cally pure water at 4° C. (ND)

GRAVITY WIND — A wind (or componentthereof) directed down the slope of anincline and caused by greater air densitynear the slope than at the same levels somedistance horizontally from the slope. Thisterm ueually is applied when the densitydifference is produced by surface coolingalong the incline, as in the case of a moun-tain wind. (AMS) *

GRAY-BROWN PODZOLIC! SOIL — Pedolo-gu. A zonal great soil group consisting ofsoils with a thin, moderately dark Al hori-zon and with a grayish-brown A2 horizonunderlain by a B horizon containing a highpercentage of bases and an appreciablequantity of illuviated silicate clay; formedon relatively young land surfaces, mostlyglacial deposits, from material relativelyrich in calcium, under deciduous forests inhumid temperate regions. (SSS)

GREAT SOIL GROUP — Pedalogy. Any oneof several broad groups of soil with funda-mental characteristics in common. Exam-ples are CHERNOZEM, GRAY-BROWNPODZOLIC, and PODZOL. (YA)

GREENHOUSE EFFECT — The heating

MlL-STQ-l 16525 MARCH1968

effect exerted by the atmosphere upon theearth by virtue of the fact that the atmos-phere (mainly, its water vapor) absorbsand re-emits infrared radiation. In detail:the shorter wavelengths of insolation aretransmitted rather freely through the at-mosphere to be absorbed at the earth’ssurface. The earth then re-errrits this aslong-wave (infrared) terrestrial radiation, aportion of which is absorbed by theatsrnophere and again emitted. (AMS)*

GROUND (or EARTH) — 1. The conduct-ing mass of the earth, or a conductor con-nected to it through a very small impe-dance. (1S0) 2. A conductor that is con-sidered to have zero electrical potential.The electrical potential of the earth isusually taken to be zero. (1S0)

GROUND CLU’fl’ER-The pattern of radarechoes from fixed ground targete near theradar. This type of clutter tends to hideor confuse the echoes returned from nearbymoving or precipitation targets. (AMS) *

GROUND COVER — All herbaceous plantsand low growing shrubs on a specific area,and the organic materiala in various stagesof decay. (ADT)

GROUND CUSHION — A cushion of airassociated with ground effect. (AFD)

GROUND EFFECT PHENOMENON—T’hegeneration of an air cushion artificially aothat a vehicle is supported on the air cush-ion close to the ground but neverthelessriding free, hence utilizing this effect toeliminate ground friction. Ground effectmachines utilize this phenomenon. (AD)

GROUND ENVIRONMENT — 1. The envi-ronment that surrounds and affects a sys-tem or a piece of equipment that operateson the ground. (AF)

GROUND FOG—According to United Statesweather observing practice, a fog thathides less than 0.6 of the sky, and does notextend to the base of any clouds that maylie above it, (AMS) *

65



GROUND FROST—A freezing condition in-

jurious to vegetation, which is considered

to have occurred when a thermometer ex-posed to the sky at a point just above agrass surface records a minimum temper-ature (grass temperature) of 30.4” F. orbelow. (AMS) *

GROUND MORAINE—A heterogeneous ac-cumulation of earth, sand, gravel, andboulders, deposited by a glacier, ordinarilythin compared with its areal extent andusually with gently irregular topographicexpression. It is usually unstratified.Ground moraine is thought. to have accu-mulated largely by lodgment beneath theglacier ice but partly also being let downfrom the upper surface as the ice meltedor evaporated. (S&V) See MORAINE.

GROUND WATER — Water in the groundthat is in ~he zone of saturation, fromwhich wells, springs, and ground-waterrunoff are supplied. (MH)

GROUND-WATER LATERITE SOIL-Pe-dology. A great soil group of the intra-zonal order and hydromorphic suborder,consisting of soils characterized by hard-pans or concretional horizons rich in ironand aluminum (and sometimes mangan-ese) that have formed immediately abovethe water table. (SSS)

GROUND-WATER OUTFLOW — That partof the discharge from a drainage basinthat occurs through the ground water. Theterm “underflow” is often used to describethe ground-water outflow that takes placein valley alluvium (instead of the surfacechannel) and thus is not measured at aGAGING STATION. (MH)

GROUND-WATER PODZOL SOIL--Pedolo-gy. “A great soil group of the intra-zonalorder and hydromorphic suborder, consist-ing of soils with an organic mat on thesurface over a very thin layer of acidhumus material underlain by a whitish-gray leached layer, which may be as muchas 2 or 3 feet in thickness, and is underlainby a brown, or very dark-brown, cemented

hardpan layer; formed under various typesof forest vegetation in cool to tropical,humid climates under conditions of poor ●drainage. (SSS)

GROUND-WATER RUNOFF—That part ofthe runoff which has passed into theground, has become ground water, and hasbeen discharged into a stream channel asspring or seepage water. (MH)

GROUND WAVE — 1. That portion of aradio wave in proximity to and affected bythe ground, being somewhat refracted bythe lower atmosphere and diffracted by thesurface of the earth. Such a wave travelsmore or less parallel to the surface of theearth. (ND) 2. A wave formed in theground by an explosion. It can be of threetypes: longitudinal wave (compression),transverse wave (shear), and s-urfa-cewave(similar to a water ripple). It can Ix in-duced by direct ground shock (as in aground or subsurface burst) or by blasttransmitted through the air (as in anytype of burst). (AF)

GROUND ZERO — The point on the surfaceof land or water at, or vertically below orabove, the center of the burst of a nuclearweapon. (JD)

GRUS, n.— Deposits resulting from theweathering of the various minerals form-ing igneous rock. The deposits consist ofthe accumulation of countless discrete par-ticles on the surface of the rock, some-times to a depth of over one meter.

GULLY, n.— A small ravine or miniaturevalley, especially one cut by running ~ater.but through which water flows only aftera rain. (ND)

GUST, n. —.4 sudden brief increase in thespeed of the wind. It is of a more transientcharacter than a SQUALL and is followedby a lull or slackening in the wind speed.Generally, winds are least gusty over largewater surfaces and most gusty over roughland and near high buildings. Accordingto United States \veather observing prac-

66


tice, gusts are reported when the peakwind speed reaches at least 16 knots andthe variation in wind speed between thepeaks and lulls is at least 9 knots. Theduration of a gust is ueually less than 20stionds. (AMS) *

GYROSCOPE, DIRECTIONAL — A gyro-scopic instrument for indicating direction,containing a free gyroscope which holds itsposition in azimuth and thus indicates an-gular deviation from a pre-set heading.(AF)

H

HAIL, n.— Precipitation in the form of smallballa or pieces of ice (hailstones) with adiameter ranging from 5 to 50 mm (0.2 to2.0 in.) or sometimes more, falling eitherseparately or agglomerated into irregularlumps. Hail falls are generally observedduring heavy thunderstorms. (WMO)

HAILSTONE, n.— A single unit of hail,ranging in size from that of a pea to that ofa grapefruit (i.e,, from lees than IA inch tomore than 5 inches diameter). Hailstonesmay be spheroidal, conical, or generally ir-regular in shape. The spheroidal etones, themost common form, typically exhibit a lay-ered interior structure resembling an onion,with alternate layers composed of GLAZEand RIME. (AMS) ●

HALF-BOG SOIL — Pedology. A great soilgroup, of the intrazonal order and hydrom-orphic subcmder consisting of wil withdark-brown or black peaty material overgrayish and rust mottled mineral soil;formed under conditions of poor drainageunder foreat, sedge, or grass vegetation incool to tropical humid climates. (SSS)

HALF-LINE — The time required for a sys-tem decaying at an exponential rate (suchse an element in radioactive disintegration )to be reduced to on~half its initial size,amount, or intensity. (AMS) *

●HALF THICKNESS — Thickness of absorb-

67

MlL-ST&l 16S25 MARCH1968

ing material necessary to reduce by one halfthe intensity of radiation which passesthrough it. (AD)

HALOMORPHIC SOIL9 — PecfQlogI/.A sub-order of the intrazonal soil order, consist-ing of saline and alkali soils formed underimperfect drainage in arid regions andincluding the great soil groups SOLON-CHAK or Saline soils, SOLONETZ soils,and SOLOTH soils. (SSS)

HAMMADA, n. — A desert surface that iseither bedrock or else bedrock covered onlyby a very thin veneer of aand or pebbles.The term was originally applied in theSahara (where it referred to a desertplateau of stones) but is now used forsimilar desert surfaces in other parts ofthe world. (S&V) *

HARBOR, n. — A restricted body of water,an anchorage or other limited coastal wa-ter area and its mineable water approach-es from which shipping operations areprojected or supported. Generally, a har-bor is a part of a base, in which case theharbor defense force forma a componentelement of the base defense force estab.lished for tbe local defense of the base andits included harbor. (JD)

HARD BEACH — A portion of a beach es-pecially prepared with a hard surface ex-tending into the water, employed for thepurpose of loading or unloading directlyinto or from landing ships or landingcraft. (JD)

HARD FROST — See BLACK FROST.

HARDNESS, n. — A combination of proper-ties of a substance determined by arbitrarytests, such as the resistance of the sub-stance to indenting or scratching by speci-fic objects. There are many arbitraryscalee of hardness, probably no two ofwhich measure the same combination ofbasic properties. Metals are usually testedby indenting them with a hard geometricalobject under specific loads using the Bri-nell, Rockwell, Diamond Pyramid Hard-ness, or Knoop tests or by a rebound test



such as the Scleroscope. The relative hard-ness of a mineral can be determined bycomparing it with a standard series ofmaterials. (S&V)

HARDPAN, n.— Pedobgv. A hardened soillayer, in the lower A or in the B horizon,caused by cementation of soil particleswith organic matter or with materials suchas silica, s~squioxides, or calcium carbon-ate. The hardness does not change appre-ciably with changes in moisture contentand pieces of the hard layer do not slakein water. (SSS)

HARD WATER, n.— Water characterizedby the presence of dissolved mineral salts,especially those of magnesium and calcium.(s&v)

HARDWOOD, n.—Generally, one of the bq-tanical group of trees that have broa~leaves, in contrast to the conifers; alsowood produced by such trees regardless oftexture (SAF)

HARMONIC, n.— 1. A sinusoidal quantityhaving a frequency that is an integral mul-tiple of the frequency of a periodic quan-tity to which it is related. (ASA) 2. Awave of vibration having a frequencywhich is an integral multiple of the funda-mental (lowest ) or other reference fre-quency of vibration of a physical system.(AMS) *

HAZE, n.— A suspension in the air of ex-tremely small, dry particles invisible tothe naked eye and sufficiently numerous togive the air an opalescent appearance.Haze imparts a yellowish or reddish tingeto distant bright objects or lights seenthrough it, while dark, objects appear blu-ish. This effect is mainly a result of scat-tering of Iigbt by the haze particles. Theseparticles may have a color of their ownwhich also contributes to the coloration ofthe landscape. (WMO)

HEADWIND, n. — A wind which opposesthe intended progress of an exposed, mov-ing object, e.g., rendering an airhrne ub-

ject’s airspeed greater than its ground-speed; the opposite of a TAILWTND.(AMS)

HEAT, n.— A form of energy transferredbetween systems by virtue of a differencein temperature, and existing only in theprocess of energy transformation. By thefirst law of thermodynamics, the heat ab-sorbed by a system may be used by the sys-tem to do work or to raise its internalenergy. (AMS)

HEAT BALANCE — 1. The equilibriumwhich exists on the average between theradiation received by the earth and atmo-sphere from the sun and that emitted bythe earth and atmosphere. That the equil ib-rium does exist in the mean is demonstratedby the observed long-term constancy of theearth’s surface temperature. (.AMS) * 2.The equilibrium which is known to existwhen all sources of heat gain and loss for agiven region or body are accounted ,for. Ingeneral this balance includes advecti~’e,evaporative (etc. ) terms as well as a radia-tion term. (AMS)

HEAT BUDGET, ANN.UAL — The amountof heat necessary to raise a body of water,such as a lake, from the minimum temper-ature of winter to the maximum tempera-ture of summer. (MH)

HEAT CAPACITY — The ratio of the heatabsorkd (or released) by a system to thecorresponding temperature rise (or fall).(AMS) *

HEAT EQUATOR — The line which circum-scribes the earth and connects all points ofhighest mean annual temperature for theirrespective longitudes. (AMS) *

HEAT, LATENT — The heat released or ab-sorbed per unit mass by a system in a re-versible, isobaric-isothermal change ofphase. In mmeoroloagy, the latent heats ofVAPORIZATION [or CONDENSATION),FUSION”. and SUBLIMATION of watersubstance wc of importance. At O“C theseare, respcmir~ly,

68


“* L, = 597.3 cal/gmL, = 79.7 caI/gmL, = 677.0 cal/gm (AMS)

HEAT RESISTANCE — The ability of a ma-terial to show little or no deterirmation oncontinuous or intermittent exposure to apredetermined elevated temperature.

HEAT, SPECIFIC — The heat capability ofa system per unit mass, i.e., the ratio ofthe heat absorbed (or released) by unitmass of the system to the correspondingtemperature rise (or fall). (AMS) “

HEAT TRANSFER — The transfer or ex-change of heat by RADIATION, CON-DUCTION, or CONVECTION in a fluidor between “the fluid and its surroundings.These three processes occur simultaneous-ly in the atmosphere, and it is often dit7i-crdt to assesa the contributions of theirvarious effects. (AMS ) *

HEAT TRANSFER COEFFICIENT — 1. Anon-dimensional number arising in the

‘oproblem of heat transfer in fluids. (AMS) *2. The rate of heat transfer per unit areaper unit temperature difference, a quan-tity having the dimensions of reciprocallength. (AMS)

HEAT WAV&A period of abnormally anduncomfortably hot and usually humidweather. To be a “heat wave” such a per-iod should last at least one day, but con-ventionally it lasts from several days toseveral weeks. (AMS)

HEDGEROW, n.- A linear thicket ofbushes, commonly with some trees, leftbetween two fields of cleared land, orplanted in order to separate fields; espe-cially common in parts of England andFrance.

HELIOGRAPH, n. – An instrument whichrecords the duration of sunshine and ~ves aqualitative measure of the amount of s.m-sfrine by the action of the sun’s rays uponblueprint paper; a type of sunshine re-

●corder. (AMS)


HERB, n. — Any flowering plaut without apersistent or woody stem above theground. Herbs include all small seed plants,including graases, (ADT) *

HERBICIDE, n.— Any preparation used tokill or inhibit the growth of plants. (AD)

HERMETIC, adj. — Made impervious to airand other fluids by fusion; originally ap-plied to the closing of glass vessels byfusing the ends; and by extension to anymode of air-tight closure.

HERTZ (Pi. HERTZ or HERTZES), n.— Aunit of frequency or a periodic processequal to one cycle per second. AbbreviatedHz

HIGH, n.— In meteorology, elliptical for“area of high pressure” referring to amaximum of atmospheric pressure in twodimensions (closed isobars) in the synop-tic surface chart, or a maximum of height(closed contours) in the constant-pressurechart. Since a high is, on the synopticchart, always associated with anticycloniccirculation, the term is used interchange-ably with ANTICYCLONE. CompareLOW. (AMS)

HIGH ALTITUDE — Conventionally, an al-titude above 10,000 meters (33,000 feet).(JD)

HIGHLAND, n.— A relative term denotingtbe higher land of a region; it may includemountains, valleys, and plains. (GS)

HOARFROST, n.— A deposit of interlock-ing ice crystals formed by direct SUBLI-MATION on objects, usually those of smalldiameter freely exposed to the air, such astree branches, plant stems and leaf edges,wires, poles, etc. Also, frost may form onthe skin of an aircraft when a cold air-craft flies into the air which is warm andmoist or when it passes through air thatis supersaturated with water vapor. Thedeposition of hoarfrost is similar to theprocess by which DEW is formed, exceptthat the temperature of the befrosted ob-ject must be below freezing. (AMS) *

69



HOGBACK, n.— A long sharp ridge carvedby differential erosion from a steeply dip-ping resistant layer or series of layers ofigneous or sedimentary rock. The term isusually restricted to ridges carved frombeds dipping at angles greater than 20degrees; beds dipping at. angles of Iess’than20 degrees give rise to CUESTAS, In ahogback the two slopes are approximatelyequal in steepness; in a cuesta the escarp-ment slope is notably steeper than the dipslope. (S&V)

HORIZON, n.—One of several lines or planesused as reference for observation andmeasurement relative to a given locationon the surface of the earth, and referredgenerally to a horizontal direction (i.e., atright angles to the zenith). (AMS) *

HORST, n. — A long narrow block of theearth’s crust that has been relatively up.lifted between’ faults along the sides. Al-though a horst may appear as an elevatedridge the term applies to fundamentalstructure and not topographic expression:Compare GRAB EN. (S&V)

HUMID TROPICS — Those areas in whichthe average temperature of the coldestmonth is above 64.4 degrees Fahrenheitand the annual rainfall rate exceeds theannual evaporation rate. These lands arecharacterized by rainforest, jungle, andsavanna vegetation. (AD)

HUMIDIFICATION, n.— A process for in-creasing the water content of air or othergases.

HUMIDITY, n.—The amount of water vaporin the air. (ND) See ABSOLUTE HU-MIDITY, RELATIVE HUMIDITY, andSPECIFIC HUMIDITY.

HUMIDITY, CRITICAL — The relative hu-midity above which the atmospheric cor-rosion rate of a given metal increasessharply. (ECS)

HUMMOCK, n.— A rounded or conical knollor hillock; a rise of ground of no greatextent, above a level surface. (S&V)

HUMUS, n. — That more or less stable frac-tion of the soil organic matter remainingafter the major portion of added plant andanimal residues have decomposed. Usuallyit is dark colored. (SSS) *

HURRICANE, n. - See TROPICAL CY-CLONE.

HURRICANE-FORCE WIND—In the Beau-fort wind scale, a wind whose speed is 64knots (73 mph) or higher. (AMS) *

HYDROGEN-ION CONCENTRATION – Theacidity. or alkalinity of a solution measuredin grams of hydrogen ions per milliliter. Itis abbreviated as pH, and is expressed interms of the negative logarithm of theconcentration (i.e., pH 7 = 10-7 grams ofhydrogen per milliliter). A pH of 7 isneutrsf; numbers below 7 denote increasingacidity with decreasing PH value; numbersabove 7 denote increasing alkalinity withincreasing pH values.

HYDROGRAPHY, n. — A graphical represen-tation of stage or discharge at a point ona stream as a function of time. me meetcommon type, the observed hydrography,represents river gage readings plotted attime of observation. (AMS) *

HYDROGRAPHIC CHART — A nauticalchart showing depths of water, nature ofbottom, contours of bottom and coastline,and tides and currents in a given sea orsea and land area. (JD)

HYDROGRAPHIC DATUM — The plane ofreference of soundings, depth curves, andelevations of foreshore and offshore fea-tures. (AD)

HYDROLOGIC BUDGET — An accountingof the inflow to, outflow from, and storagein, a hydrologic unit, such as a drainagebasin, aquifer, soil zone, lake, reservoir,or irrigation project. (MH)

HYDROLOGIC CYCLE—A convenient termto denote the circulation of water from thesea, through the atmosphere, to the land;and thence, with many delays, back to the

70


sea by overland and subterranean routes,and in part by way of the atmosphere; alsothe many short circuits of the water thatis returned to the atmosphere withoutreaching the sea. (MH)

HYrmoLoGIc tiEOMETRY FEATURE —A channel, stream, pand, lake, or otherdepression which exhibits a water depth of25 cm or greater fora total period of atleast one week of the year, (WES)

HYDROMETER, n.— Any product of con-densation or sublimation of atmosphericwater vapor, whether formed in the freeatmosphere or at the earth’s surface; also,any water particles blown by the windfrom the earth’s surface. (AMS) *

I HYDROMORPHIC SOILS — Pedobgy. A

I suborder of intrazonal soils, consisting ofseven great soil groups, all formed underconditions of poor drainage in marshes,seepage areas, or flata. (SSS)

0“”

*

HYDROPHILIC, adj. — Having an attrac-tion for water, i.e., readily wet by water,said of films capable of swelling in water.

HYDROPHOBIC, adj. — Having little or noaffinity for water. Water repellent or notwet by water.

HYDROPHYTE, n.— A plant that typicallygrows in water or in saturated soil. Hydro-phytes may be rooted or free floating; sub-merged, with floating leaves; or with leavesemergent above the water level.

HYDROSPHERE, n.— The water portionof the earth as distinguished from the solidpart, called the LITHOSPHERE, and fromthe gaseous outer envelope, called the AT-MOSPHERE. (.4MS)

HYETOGRAPH, n.— 1, A chart showingrainfall intensity against time. 2. A mapshowing the areal distribution of rainfall.(AMS) “

HYGROMETER, n.— An instrument formeasuring the water vapor content of theair. The most common type is a PSY-CHROMETER, consisting essentially of


dry-bulb and wet-bulb tbermometere.(AMS) *

HYDROSCOPE, n. — An instrument whichindicates variation in atmospheric mois-ture. (ND)

HYDROSCOPIC, adj. — 1. Pertaining to amarked ability to accelerate the condensa-tion of water vapor. (AMS) * 2. Descrip-tive of a substance, the physical charac-teristics of which are appreciably alteredby effects of water vapor. (AMS) *

HYGROTHERMOGRAPH, n.—A recordinginstrument combining, on one record, thevariation of atmospheric teinperature andhumidity content as a function of time.The most common hygrothermograph isa hair hygrograph combined with a ther-mograph. (AMS)

HYPERSONIC, adj. — Of or pertaining tospeeds equal to or in excess of five timeethe speed of sound. (JD)

HYPSOMETER, n.— 1. An instrument formeasuring atmospheric pressure by de-termining the biting point of a liquid atthe station. (AMS) ● 2. An instrument fordetermining the height of trees or otherobjects.

HYSTERESIS—An effect, involving energyloss, found to varying degrees in magnetic,electric, and elastic media when they aresubjected to variation by a cyclical appliedforce. In such media the polarization orstress is not a single-valued function ofthe applied force, or, stated in anotherway, the condition of the medium dependson its previous history as well as the in-sbntaneous value of the applied force.May be visualized as resulting from somekind of internal friction.

I

ICAO STANDARD ATMOSPHERE — SeeATMOSPHERE, STANDARD.

ICE, n.— The solid form of water, in natureformed either by (a) the freezing of water,

71



as in the case of river or sea ice;’ (b) theconversion of atmospheric water vapor di-rectly into ice crystals; (c) the compac-tion of snow-, with or without the motionof a glacier; or (d) the impregnation ofporous snow masses with water which sub-sequently freezes. (IG ) *

ICEBERG, n.— A large mass of detachedland ice floating in the “sea or stranded inshallow water. Irregular icebergs gener-ally calve from glaciers, whereas tabularicebergs and ice islands are usually formedfrom shelf ice. Icebergs are the largestform of floating glacier ice, BERGY BITSand growler-s being generally the frag-ments of broken icebergs. (NOO)”

ICE BLINK — A relatively bright, usuallyyellowish-white glare on the underside ofa cloud layer, produced by the reflection onthe clouds of an ice-covered eurface aspack ice. (AMS) *

ICECAP, n.— Any ice sheet covering a largeportion of a land area; e.g., the GreenlandIcecap. (ADT)

ICE, CLEAR — Generally, a layer or massof ice which is relatively transparent be-cause of its homogeneous structure andsmall numbw and size of air pockets.(AMS) *

ICE CRYSTAL — Any one of a number ofmacroscopic crystalline forms in which iceappears, including hexagonal columns,hexagonal platelets, dentritic crystals, iceneedles, and combinations of these forms.(AMS)*

ICE FIELD — A large, level area of ice,either of sea ice (“more than five milesacrosk”) or an ICECAP or highland ice.(AMS)

ICE FOG — A type of fog, composed of sus-pended particles of ice, partly ice crystals20 to 100 microns in diameter but chiefly,especially with dense, tiny ice particles 12to 20 microns in diameter. It occurs at verylow temperatures, and usually in clear,calm weather in high latitudes. Also called

t~ozen foo, POgOniP, etc. (AMS) -

ICE FROST — Specifically, a thickness ofice that gathers on the outside of a rocket ●vehicle over surfaces supercooled by liquidoxygen inside the vehicle. This ice frost isquickly shaken loose and falls to the groundonce the vehicle begins its ascent. (AF)

ICE ISLAND — One of the. many, large tabular icebergs found in the Arctic Ocean,The. area of the largest one known is about300 square miles. They are about 150 feetthick over all, and drift with ocean cur-rents rather than with the wind. (AMS) “

ICE LENS — 1, A discontinuous layer ofground ice tapering at its extremities. Icelenses ‘in soils occur roughly parallel toeach other, generally coincident with thedirection of heat loss, and commonly inrepeated layers. ‘2. A discontinuous hori-zontal ice band in FIRN or SNOW whichtapers at its extremities. (ADT)

ICE NEEDLE — A long, thin ice crystaiwhose cross-section Demendicu]ar to itslong dimension is ~yp~cally hexagonal.(AMS)” ●

ICE PELLETS — Precipitation of transpar-ent or translucent pellets of ice, which arespherical or irregular, rarely conical, antiwhich have a diameter of 5 mm (0.2 in. )or less. Ice pellets include SLEET (U. S,definition)’ and SMALL HAIL. (WMO) *

ICE PRISMS — A fall of unbranched ICECRYSTALS, in the form of needles, co-umns, or plates often so tiny that theyseem to be suspended in the air. Thesecrystals may fall from a cloud or from :1.cloudless sky. (WMO) *

ICE SHEET — Any large area of continuousice overlying a land surface. (NOO) It iscontinental ice or ICECAP if it is an icesheet of vast extent, covering and floodiugirregularities of a large land mass; orhiahland ice if it is a comuarativelv tk i:)ice cover conforming generallyregularities of the land. (ND) *

to t_he ir

●7’2


; ‘o

●

ICE SHELF — 1. A thick ice formation witha fairly level surface, formed along a polarcoast and in shallow, bays and inleta, whereit is fastened to the shore and often reach-es bottom. It may grow hundreds of milesout to sea, It is usually an extension ofland ice, and the seaward edge floats freeIyin deep water. 2. More specifically, a levelice formation over 2 meters (6.6 feet)above the sea surface which originatesfrom annual accumulations of FIRN snowlayers on bay ice or on the seaward exten-sion of a glacier. (NOO ) *

ICE WEDGE — A vertical sheet of groundice which tapers downward. Also calledground ice wedge. (ADT)

ICING, n.— 1. In general, any deposit orcoating of ice on an object, caused by theimpingement and freezing of liquid (usual-ly supercooled) hydrometeors. (AMS) * 2.A mass or sheet of ice formed on theground surface during the winter by suc-cessive freezing of sheets of water thatmay seep from the ground, from a river,or from a spring. (AMS) ●

IGNEOUS ROCKS—Rocks formed by solidi-fication of hot mobile rock material (mag-ma) including those formed and cooled atgreat depths (plutonic rocks), which arecrystalline throughout, and those whichhave poured out on the earth’s surface inthe liquid state or have been blown asfragments into the air (votcanic rocks).(s&v)“

ILLUVIATION, n.— An accumulation ofmaterial in a soil horizon through the dep-osition either mechanically or chemicallyof suspended mineral and organic matteroriginating from horizons above. Since atleast part of the fine clay in the B horizons(or subsoils) of many soils has moved intothem from the A horizons above, these arecalled Wcmtil horizons. (YA)

IMBIBITION, n.— 1. The absorption by agel of a liquid for which it has an affinity.Imbibition is accompanied by an expan-sion or swelling of the gel. 2. The process


by which plants absorb water from theaoil. (AMS)

IMMATURE SOIL — PeoWogy. A soil lack-ing clear individual horizons because of

. the relatively short time for soil-buildingforces to act upon the parent material sinceits deposition or exposure. (YA)

HMMERSION PROOF — Unless otherwisespecified, immersion proof means that anitem of equipment when ready for fieldtransport can be submerged for 2 hoursin salt or fresh water to a covering depthof 3 feet, and be capable of operating atnormal effectiveness immediately afterbeing removed from the water. (AD)

IMPACT, n.— A single collision of one massin motion with a second mass which maybe either in motion or at rest. (ASA)

IMPACT ACCELERATION — A sudden ac-celeration caused by impact, as occurs,e.g., in a crash landing. (NASA)

IMPEDANCE, n.— The ratio of two com-plex quantities both of whose arguments -increase linearly with time at” the samerate. The numerator of the ratio representsan excitation and the denominator repre-sents the response. Impedance is expreseedas a function of frequency. ( ISO) *

IMPEDANCE, ANGULAR MECHANICAL— The ratio of torque to angular velocity.(SVH)

IMPEDANCE, DRIVING POINT — In amechanical structure, the ratio of forceto velocity *hen both the force and velocityare measured at the same point and in thesame directiori. (SVH)

IMPEDANCE, MECHANICAL — The ratioof a force-like quantity to a velocity-likequantity when the arguments of the real(or imaginary) parts of the quantities in-crease linearly with time. (SVH )

IMPEDANCE, TRANSFER — 1. Betweentwo points in a mechanical structure, theratio of force to velocity when force ismeasured at one point and velocity at theother point. 2. At the same point in a me-

73


MlL-STD-l 165 ‘25 MARCH 1968

chanical structure, the ratio of force tovelocity when force and velocity are meas-ured in different directions. (SVH)

. IMPULSE, n.— The product of a force andthe time during which the force is applied.(ISO)*

INCANDESCENCE, n.— Emission of lightdue to high temperature. Any other emis-sion of light is ulled LUMINESCENCE.(ND)

INCENDIARY, n. - Any chemical agent de-signed to cause combustion, used especiallyas a tilling for certain bombs, shells, bul-lets, or the like. (AFD)

INDICATOR, n.— 1. That part of electronicequipment in which the data is obtainedby observation. This is usually in the formof a scope or dial. (ND)* 2. That part ofan instrument from which the reading ismade. This may be at the instrument or ata remote Iocation, or both. (ND)

INDUCED ENVIRONMENT — Any man-made or equipment-made environmentwhich directly or indirectly affects the per-formance of man or” materiel. (JD)

INDUCED RADIATION — Radiation pro-duced as a result of exposure to radio-active materials, particularly the captureof neutrons. (JD)

INDUCTANCE, n.— .Electricity. The ,prop-erty of an electric circuit that induces anelectromotive force into the circuit its~lfor into a nearby circuit, which force op-poses any introduction, charge, or d~scon-tinuance of the current. Inductance corre-spends, ~o inertia in matter. It is the prop-erty that causes a lag in time for a currentjust turned on to rise to its full value.(AFD)

INERT, adj. — Destitute of power to moveitself or actively to resist motion im-pressed; not having active properties; pow-erless for a desired effect.

INERTIA, n.— The property of matter bywhich it resists any change in its state of

rest of uniform motion in a straight line.(ND) ●

INFILTRATION, n.— 1. The flow of a fluidinto a substance through pores or smallopenings. It connotes Ro\v into a substancein contradistinction to the word percola-tion, which connotes flow through a poroussubstance. ( MD) 2. The downward entryof water into the soil. (SSS)

INFILTRATION CAPACITY — The maxi-mum rate at which the soil, when in agiven condition, can absorb falling rain ormelting snow. (ivIH)

INFILTRATION INDEX—An average rateof infiltration, in inches per hour, equal tothe average rate of rainfall such that thevolume of rainfall at greater rates equalsthe total direct runoff, (MH)

INFRA~.ED RADL4TION ~ Electromag-netic radiation in the wavelength regionbetween visible radiation and microwaveradiation; usually considered to begin at7600 A (0.76 mic_ron) and extend to- 1,000microns (1 mm), ●

INFRASONIC FREQUENCY — Frequencylying below the audio frequency range.(ASA)

INHERITED SOIL CHARACTERISTIC —Any characteristic of a soil that is duedirectly to the nature of the material fromwhich it formed, as contrasted to the char-acteristics that are wholly or partly theresult of soil-forming processes acting onparent material. For example, some soilsare red because the parent material wasred; although the color of most red soilsis due to soil-forming processes. (YA)

INHIBITOR, n. — 1. .h agent that slows orinterferes \vith a chemical action. 2. A sub-stance which effectively decreases the cOP,.ROSION rate of a metal when added insmall amouctts to the corrosive environ-ment. (ECS) ‘ 3. A substance added to cer-tain propell+mts to reduce hygroscopicityor the tendency to absorb moisture. (AFD)

74 ●


/“o INITIAL RADIATION — The nuclear radi-ation accompanying #, nuclear exp]o~ionand emitted from the resultant fireball;immediate radiation. (JD)

INLET, n.— A smalI, narrow bay or creek;a small body of water leading into alarger; a narrow strip of water runninginto the land or between islands. (GS )

IN PLACE — 1. Formed or accumulated onthe spot. A rock may decay and breakdown into small particles where it is firstexposed in the land surface. It is then saidto have weathered in place or in situ. (YA)2. AS a mass appears in the soil before anydisturbance, For example, the deeper partof a profile may be massive and show nosigns of structure in place but break downinto lumps of regular size and shape whenremoved. (YA)

INSELBERG, n.— A small mountain or hillstanding above a desert pediment or pene-plain. It is surrounded by more or less

●level rock surfaces or by debris derivedfrom and overlapping its slopes. (S&V)

INSOLATION, n.—l. In general, solar radi-ation received at the earth’s surface.(AMS) 2. The rate at which direct solarradiation is incident upon a unit horizontalsurface at any point on or above the sur.face of the earth, (AMS)

INSTRUMENT SHELTER — A Imx-likestructure designed to protect certain m<,e-orological instruments from exposure todirect sunshine, precipitation, and condm-eation, while at the same time providingadequate ventilation. Instrument sheltersare painted white, have louvred sides,usually a double roof, and are moul-.ted ona stand several feet above the ground withthe door side facing poleward. (AMS) *

INSULATE, v.t. — To separate or isolate aconducting body from its surroundings, bymeans of a nonconductor. as to nreventtransfer of electricity, l~eat, or” sound.(ND)

●INSULATION, n.— A material havi,;g rela-

75


tively high resistance to heat flow, elec-tricity, or sound.

INSULATION RESISTANCE — The meas-ured resistance of the insulation of a deviceor product. Thk measurement is takenalong the path over which the insulationis intended to be effective,

INTENSITY LEVEL (or SOUND-ENER-GY FLUX DENSITY LEVEL) — SeeSOUND INTENSITY LEVEL.

INTERFACE, n.—A surface separating twomedia across which there is a discontinuityof some property, such as density, velocity,etc., or of some derivative of one of theseproperties in a direction normal to theinterface, (NOO)

INTERFERENCE, n. — 1. Extraneous sig-nals, noises, etc. that hinder proper recep-tion, transmission, or recording of thedesired signal in eie,:tronic equipment.(ND) 2. The mutua! effect of two or moremeeting waves or vibrations of any kind.Sometimes called wave i?ztes-ference. (ND)3. The aerodynamic influence of two ormore budies on each other. (ND)

INTERFERENCE, ACOUSTIC — The com-bined action of two wavee moving simul-taneously through the same region. Twowaves of the same frequency, in phasewith each other, and moving in the samedirection, produce reinforcement. Twowaves of the same frequency, in phase op-position, and moving in the same direction,produce destructive interference; if furtherthey have equal amplitudes, the result isa complete annulment.

INTERFERENCE, OPTICAL — The com-bined action of two light rays, Unless thetwo paths are of identical optical length,the two beams may not be in phase, andcan destructively interfere at some points(dark) and constructively interfere atother points (bright ). The principle of theconservation of energy applies; and, there-fore, the energy missing in the darkpoints will be found in the bright points.


MIL-STD-116525 MARCH 1968

INTERFEROMETER, n. — An apparatusused to produce and show interference be-tween two or more wave trains comingfrom the same luminous area, and also tocompare wave lengths with observable dis-placements or reflectors, or other parts, bymeans of interference fringes. An interfer-ometer is frequently used to obtain quan-titative information on flow around bdiesin wind tunnels.

INTERFLOW, n.—The water, derived fromprecipitation, that infiltrates the soil iur-face and then moves laterally through theupper layers of soil above the water tableuntil it reaches a stream channel or re-turns to the surface at some point down-slope from its point of infiltration. (AMS)

INTERFLUVE, n. – 1. The area betweentwo rivers; especially, a more or lessundissected upland between two adjacentstreams flowirrg in more or Iesa par~elcourses. (S&W 2. The surface area ofALLUVIAL FANS between DRYWASHES.

INTERMEDIATE SCALE MAP — A map,normally of a scale from 1:200,000 to1:500,000, intended for planning strategicoperations, including the movement, con-centration, and supply of troops. (JD ) Seealso MEDIUM-SCALE Lhf.4P.

INTERMITTENT STREAM — A streamthat flows only part of the time. It may beeither an ephemeraI stream, which floysfor a few hours or days after rain, ‘or aseasonal stream, which flows for severalmonths, of the year, as during the rainyseason O! during the season of snow melt.

INTERTROPICAL CONVERGENCE ZONE— The axis, or a portion thereof, of thebroad trade-wind current of the tropics.This axis is the dividing line between thesoutheast trades and the northeast trades(of the Southern and Northern Hemis-phere, respectively). (AMS) *

INTRAPERMAFROST WATER — Groundwater within the PERMAFROST. (AD)

INTRAZONAL SOIL — Pedology. Any oneof the great groups of soils having moreor less “well-developed soil characteristicsthat reflect a dominating influence of somelocal factor of relief or of parent materialover the normal influences of the climateand the vegetation on the soil-formingprocesses. Such groups of soils may be‘geographically associated with two ormore Jf the zonal groups of soils havingcharacteristics dominated by the influenceof climate and vegetation. (YA)

INTREN”CHED MEANDER — A meanderinclosed by valley walls. (SW)*

INTRUSION, n.— The process of forcibleemplacement of one body of mobile rockmaterial into or between other rocks. Theterm generally refers to the invasion ofolder rocks at depth by molten rock ormagma; but it is also used to describe theplastic injection of salt domes into over-lying rocks. (S&V)

INTRUSIVE ROCK, n.— Igneous rock thathas ascended in a hot mobile state from thedepths of the earth, but that has beenarrested and cooled before reaching thesurface. The forms usually assumed byintrusive rocks are tabular or sheet-likedike’s and silf.s, cylindrical necks, and largermasses with steep walls and no apparentfloor, such as stocks and bathokths. (S&V)

INVERSION, n.— In meteorology, a depar-ture from the usual decrease or increasewith altitude of the value of an atmos-pheric property; also, the layer throughwhich this departure occurs (the “inver-sion layer”), or the lowest altitude atwhich the departure is found.. (the “baseof the inversion”). This term almost al-WaYSmeans, a temperature inversion; how-ever, a moisture inversion and precipita-tion inversion are also defined. (AIMS)

IONIZATION, n.— The process by whichneutral atoms or groups of atoms becomeelectrically charged, either positively ornegatively, by the loss or gain of electrons;or the state of a substance whose atoms or

76.


‘-0 groups of atoms have become thus charged.(ND)

IONIZATION CHAMBER — An instrumentconsisting essentially of a closed chamberor tube of air or gas with two electrodes,used for detecting and measuring nuclearradiation. Radiation passing through anionization chamber ionizes the air or gasin the chamber, permitting detection andmeasurement of the radiation by electricalmeans. (AFD)

IRRIGATION — The controlled applicationof water to arable lands to supply waterrequirements not satisfied by rainfall.(MH)

ISALLOBAR, n.— A line of equal changein atmospheric pressure during a specifiedtime interval; an isopleth of pressure ten-dency. (AMS) *

ISOBAR, n.— A line of equal or constantpressure; an isopleth of pressure. In mete-orology, it most often refers to a line

m

drawn through all points of equal atmos-pheric pressure along a given referencesurface, such as a constant-height surface(notably mean-sea-level on surface charts).(AMS) *

lSOHYET. n.— A line drawn through geo-graphical points recording equal amountsof precipitation during a given time periodor for a particular stcrrn. (AMS)

ISOLATION, n.— A reduction in the ca-

; pacity of a eystem to respond to an excita-tion attained by the use of a resilient sup-port. In steady-state forced vibration, iso-

1 lation is” expressed quantitatively as theI

complement of TRANSMISSIBILITY.(ASA)

ISOLATION EFFICIENCY — See TRANS-MISSIBILITY.

ISOLATOR — In shock and vibration me-chanics, a device or system which reduces(the magnitude of motion transmitted froma vibrating foundation to the equipment,

●or reduces the magnitude of force trans-

77


mitted from the equipment to its founda-tion. (SVH)

ISOPLETH, n.— 1. A line of equal or con-stant value of a given quantity, with re-spect to either space or time. (AMS) * 2.A line drawn through points on a graphat which a given quantity has the samenumerical value (or occurs with the samefrequency) as a function of the two co-ordinate variables. (AMS ) 3. A straightline along which lie corresponding valuesof a dependent and independent variable.(AMS)

ISOPYCNIC, adj. — Of equal or constantdensity, with respect to either space or time(AMS)”

ISOTHERM, n. — A line of equal or constanttemperature. (AMS)”

ISTHMUS, n.— A narrow strip of land con-necting two considerable bodies of land.(GS)

J

JAMMING, n. — Intentional transmissionor re-radiation of radio signals in such away as to interfere with reception of de-sired signals by the intended receiver.(ND)

JERK, n.— A vector that specifies the timerate of change of acceleration ‘with respectto an inertial reference frame. Jerk is thefirst derivative of the acceleration with re-spect to time. (1S0)

JETTY, n.— A structure, such as a wharfor pier, so located as to influence current orprotect the entrance to a harhr or river.A jetty extending into the seato protect thecoast from erosion is called a w-oh. A jettywhich breaka the force of the sea at anyplace is called a breakwater. A jetty, wall,or bank, often submerged, built to director confine the flow of a river or tidal cur-rent is called a training wall. A wall or em-



bankment along a waterfront, to resist en-croachment of the s-, is called a sea WUU.(NOO)

JOLT TEST — The application of repeatedshocks to equipment.

JUMBLE TEST — The application of re-peated tumbling to equipment in a boxbeing rotated around its diagonal axis.

JUNGLE, n. — A dense, tangled second-growth vegetation of grasses, shrube, smalltrees, and vines; generally associated withequatorial areas. The term is often usedimproperly as a synonym for TROPICALRAINFOREST, which is relatively clearof undergrowth.

K

K — Abbreviation for KELVIN TEMPERA-TURE SCALE.

K FACTOR (Also called MULTIPLICA-TION FACTOR) — The ratio of the num-ber of neutrons produced by nuclear fissionto the number of neutrons originally pres-ent in a fission reactor — in other words,the number of neutrona produced in a chainreactor for every neutron absorbed or other-wise lost. In order to obtain a useful con-trolled reaction, the multiplication factormust be kept at a value of k equal to orslightly greater than one.

KAME, n.— A fluvio-glacial deposit occur-ring as a mound, knob, or hillock in whichone or more sides were in contact with theglacier ice. Kames are diverse in size, shape,and composition and generally, but not uni-versally, consist of poorly sorted, poorlystratified material. (S&V)

KAME TERRACE, n.— Stratified drift de-posited by meltwater between glacier iceand adjacent higher ground and left as aconstructional terrace after disappearanceof the ice. (S&V)

KARST TOPOGRAPHY — Type of land-

form developed in a region of easily solu-ble limestone bedrock. It is characterizedby vast numbers of depressions of all sizes,sometimes by great outcrops of fluted lime-stone ledges, sinks and other solution pass-ages, almost total lack of surface streams,and large springs in the deeper valleys. Thetype locality is the Karst, a limestone pla-teau on the eastern coast of the AdriaticSea. (S&V)

KATABATIC WIND — 1. Any wind blow-ing down an incline; the opposite of ana-batic wind. If the wind is warm, it is called aFOEHN; if cold, it maybe a @J wind (suchas the bora), or a gravity or drainage wind(such as a mountain wind). (AMS) *

KELVIN TEMPERATURE SCALE (ab-breviated K) — Same as ABSOLUTETEMPERATURE SCALE (see ABSO-LUTE ZERO). In the Kelvin scale, thefreezing point of water is 273.15°K (zerodegree Celsius) and the boiling pointof water is 373.15°K (1OO”C).

KETTLE HOLE— A depression found inglacial drift believed to have originatedwhen a block of ice, left isolated by gen-eral melting away of a glacier, is partlyburied by sediments and later melts entire-ly away. Kettle holes are usually undrainedand the larger ones may contain lakes andponds. (S&V)

KNOT, n.— The unit of speed in the nauticalsystem; one nautical mile per hour. It isequal to 1.1508 statute miles per hour or0.5144 meters per second. (AMS)

KONIMETER, n.— An instrument for determining the dust content of a sample ofair. One form of the instrument consistsof a tapered metal tube through which asample of air is drawn and allowed to im-pinge upon a glass slide covered with aviscous substance. The particles caught arecounted and measured with the aid of amicroscope. (AMS) Also spelled CONIM-ETER.

78


L

LACUSTRINE DEPOSIT — Material depos-ited in lake water and later exposed eitherby lowering of the water level or by the ele-vationof the land. (SSS)

LACUSTRINE TERRACES—Benches orflata which markt hes horelines of ancientlakea or earlier high-water stsgts of exist-ing lakes. Nearly horizontal surfaces withrelatively steep slopes facing the centralportion of the lake characterize this land-form.

LAG, n.— 1. That part of the difference be-tween the output of an instrument and its

input which is due to the failure of the in-strument to respond instantaneously tovariations of the input signal. It is a func-tion of the instrument’s time constant.(AMS) 2. The difference in phase betweenthe voltage and the current it produces inan inductive circuit. (AMS) * 3. Variouslydefined as time from beginning (or centerof mass) of rainfall to peak (or center ofmass) of runoff. (MH)

LAGOON, n.— A shallow sound, channel,pond, or lake, bapecially one near, or com-municating with, the sea. (S&V)

LAKE, n.— 1. Any standing body of inlandwabw, generally of considerable size. (GS)2. A pod of a viscous material, such se oilor asphalt. (GS)

LAND, n.— The total natural and culturalenvironment within which production takesplace. Land is a broader term than SOIL. Inaddition to soil, its attributes include otherphysical conditions such as mineral depositaand water supply; location in relation tocenters of commerce, populations, and otherland; the size of the individual tracta orholdings; and existing plant cover, worksof improvement, and the like. (YA) *

LANDFORM, n.— The physical exurawion

‘oof the land surface. (F-M) -


LAND LOCOMOTION MECHANICS — Anengineering discipline which integratea psr-ametera of soil mechanics, vibration re-sponse and vehicle geometry into analythxdsystems for the design of off-road automo-tive vehicles Weeeeeing optimum perform-ance, ride, and handling characteristics.

LANDSCAPE, n.— The sum total of thecharacteristics that distinguish a certakrkind of area on the earth’s surface and giveit a distinguishing pattern in contrast toother kinds of areas. Any one kind of soilis said to have a characteristic naturallandscape, and under different uses it hasone or more characteristic cultural land-scapes. (YA)

LANDSCAPE TYPE — A region through-out which a specific assemblage of environ-mental factor classes occurs and throughoutwhich factor classes are related to eachother in a similar way. (WES)

LANDSLIDE, n.— The Wrceptible down-ward and outward movement of slope.form-ing materials composed of natural rock,soils, artificial fills, or combination there-of. Landslides move along surfaces of sepa-ration by falling, slidhg, or flowing, andare differentiated from eurtlcial creep bythis more definite and deeper-eeated surfaceof rupture and by a faster rate of motion.(s&v)

LANE, n.— A clear route through an otMta-cle. A single lane is normally 8 meters wideand suitably marked; a double lane is 16meters wide. (AD) *

LANGLEY, n.— A unit of energy equal toone gram-calorie per square centimeter.

LAPSE RATE — The deerease of an atmo-spheric variable with height, the variablebehg temperature, unless otherwise speci-fied. (AMS) *

LARGE-SCALE MAP — A map having ascale of 1:75,000 or larger. (JD)

LATENT HEAT — The heat released or ab-

79



sorbed per unit mass by a system in a re-versible, isobaric-isothermal change ofphase. In meteorology, the latent heats ofvaporization (or condensation), fusion, andsublimation of water substance are of im-portance. (AMS) *

LATERAL OBSTACLE — An insurmounta-ble terrain feature or combination of suchfeatures that forces a vehicle to deviatelaterally from a desired path. (WES)

LATERITIC SOIL — A suborder of zonsdsoils formed in warm, temperate, and tropi-cal regions and including the followinggreat soil groups: Yellow Podzolic, RedPodzolic, Yellowish-Brown Lateritic, andLateritic. (SSS)

LATERIZATION, n.— A complex chemicalwea+$ering process involving increase inalumma or iron oxides, or both, and re-moval of silica. (WV)*

LAVA, n. — Fluid rock, such as that which is-sues from a volcano or a fissure in theearth’s surface; also the same materialsolidified by cooling. (GS) *

LAVA FLOW — A stream of molten lavawhich has flowed over a part of the earth’ssurface. If it spreads out over a large areait is called a farm bed or a lava /iefd. Lavaflowa or lava beds may be nearly smoothand level or they may be extremely rough.(NAS)

LAYER PRINCIPLE — A technique ofclothing design which utilizes the principle.that two or more thicknesses of clothing,with intervening air space, provide gre,aterinsulation than the same thickness of cloth-ing of the same material in a single layer.(ADT) *

LEACHING — Tbe removal of materials insolution from the soil. (SSS)

LEAD, n.— A long narrow passage throughpack ice, navigable by a surface vessel andusually large enough to allow a submarineto surface in or through it. (IG) *

LENGTH OF RECORD — The period during

which observations have been maintainedat a meteorological statiori, and whichserves as the frame of reference for clima-tic data at that station. The standard lengthof record for the purpose of a normal hasbeen fixed by the World Meteorological Or-ganization as thirty years, which is a fairpractical average for the length of a homo-geneous record desirable for most of themeteorologicril elements. (AMS ) *

LEVEE, n. - An embankment sfong theshore of a river or arm of the sea to preventoverflow. A natural levee is one built by ariver in times of flood by deposition ofmaterial upon the banks. Natural levees arerelatively low and wide. (S&V)

LIANA, ,n. — A woody climbing plant withground roots.

LICHEN, n.—Any plant of the class Lichenesvarying in size, form, and color but alwayshaving a compound structure consisting ofan alga and fungus. A lichen is an air plantwhich lacks roots, stems, branches, leaves,and flowers; it reproduces by spores orthrough fragmentation. It is usually foundattached to rocks, soil, wood, or bark.(ADT)

LIGHTFASTNESS, n.— Ability of a coloror colored material to withstand exposureto radiant energy without change from theoriginal condition.

LIGHTNING — A luminous manifestationaccompanying a sudden electrical dischargewhich takes place from or inside a cloud or,less often, from high structures on theground or from mountains. (WMO)

LIME PAN — A PLLAY,A,the iuiface layerof which is cemented by calcium carbonateprecipitated as the water evaporates. (SSS)

LIMESTONE, n.— A bedded sedimentarydeposit consisting chiefly of calcium car-bonate which yields lime when burned. (Ina broader sense the term has been used forcombinations or mixtures with magnesiumcarboriate in which the proportion of cal-

80


ID

m

cium carbonate. ia le~ than half.) (S&V)”

LIQUID-IN-GLASS THERMOMETER — Athermometer in which the thermally sensi-tive element is a liquid contained in a grad-uated glass envelope. The indication of sucha thermometer depends u~n the differencebetween the coefficients of thermal expan-sion of the liquid and the glass. Mercury andalcohol are liquids commonly used in mete-orological thermometers. (AMS)

LIQUID LIMIT — Soil Mechanics. One of themeasures of soil consistency (see ATTER-BERG LIMITS). The water content, ex-pressed as a percentage of the weight of theoven-dried soil, at the boundary betweenthe liquid and plastic states. The water con-tent at this boundary is arbitrarily definedas the water content at which two halvesof a soil cake will flow together for a dis-tance of 0.5 inches along the bottom of thegroove separating the two halves, when thecup is dropped 25 times for a distance of1 cm (0.S937 inches) at the rate of twodrope per second, (S&V)

LITHOMETEOR, n.— A meteor consistingof an ensemble of particles most of whichare solid and non-aqueous. The particles aremore or less suspended in the air, or liftedby the wind from the ground. The litho-meteors which have more or lees the char-acter of suspensions in the atmosphere arehaze, dust haze, and smoke; they consist ofvery small dust particles, of sea-saltparticles or of combustion products (e.g.from forest fires). (WMO)

LITHOSOLS ——A great soil group of azonalsoils characterized by an incomplete solumor no clearly expressed soil morphology andconsisting of freshly and imperfectly wea-thered rock or rock fragments. (SSS)

LITHOSPHERE, n.— The outer, solid por-tion of the earth; the crust of the earth; us-ually used in contexts wherein the litho-sphere is said to make contact with theATMOSPHERE and the HYDROSPHERE.(AMS)


LITTORAL, adj. & n.— Oceunographv. Thebenthic zone between high and low watermarks. According to some authorities thebenthonic zone between the shore and wa-ter depths of approximately 100 fathoms(ZOOmeters). It ia also called the littoralbenthd which ia subdivided into the eWt-torcrl and the .w.tblittorat. The usage and in-terpretation of this term varies widely inthe literature. (NOO)

LIVE ROOM — A room characterized by anunusually small amount of sound absorp-tion, or stated conversely, a room that hasan appreciable reverberation time.

LOAD FACTOR — The factor by which theweight of a piece of equipment is multi-plied to determine the steady-state acceler-ation level to be applied through the equip-ment center-of-gravity, the vaIue and direc-tion of the factor being specified for thevehicle structure location at which the itemof equipment is to be installed.

LOAD RANGE — For a shock and vibra-tion ISOLATOR, or an insulating INTER-FACE material, the range of static load orunit load which the isolator or material isdesigned to support.

LOADED HEIGHT — For a shcmk or vibra-tion ISOLATOR or mounting base, thespecified or measured distance from itsvehicle installation INTERFACE to aspecified point on the equipment side of theresilient m~lum, when a specified percentof the rated load is applied.

LOAM, n, - The U.S. Department of Agri-culture textural class name for soil havinga moderate amount of sand, eilt, and clay.Loam soils contain 7 to 27 percent of clay,28 to 50 percent of silt, and less then 52percent of sand. (YA) ●

LOAMY SAND, n.— The U.S. Departmentof Agriculture textural class name for soilcontaining more than 70 percent sand andlees than 15 percent clay, and lees then 85percent sand at O percent clay and morethan 10 percent clay at O percent silt.

81



LOCAL RELIEF —The difference in eleva-tion between the higheat and lowest @nt4in a limited area. In terrain studies, it isusually one square mile. (FM) *

LOCAL WINDS — Winds which, over a smsllarea, differ from those which would be ap-propriate to the ~neral pressure distribu-tion, or which PGSSSS some other peculiar-ity. (AMS) *

LOCAL SPEED OF SOUND — The veleeityof propagation of acoustic waves over aemall region as determined by the conditionsthere. It is principally a frmction of tem-perature.

LOESS, n.— Geological deposit of relativelyuniform, ftne material, mostly silt, presum-ably transpwted by wind. Many unlikekkrds of soil in the United States have de-veloped from 10SSS blown out of alluvial>valleys and from other deposits during pe-riods of aridity. (YA)

LOGARITHMIC DECREMENT — In shockand vibration terminology, the natural lWgarithm of the ratio of any two successiveamplitudes of like sign’ in the decay of a$ir@e-frequency OecWation. (SVH)*

LOLLY ICE — See FRAZIL.

LONGITUDINAL DUNES — Long, narrowridges of sand, parallel to the diredion ofthe prevailing winds. They are wider andsteeper on the windward side and tap6r toa point on the leeward side. Characteristic.all y, they form behind topographic obsta-cles in areas where wind is strong andvaries little in direction, and where aired isplentiful. (S&V)

LONGITUDINAL OBSTACLE — A sur-mountable terrain feature (e.g., t.d; thickgrass ) that inhibik the movement of, asurface vehicle by forcing it to SIOWdownas the ftiture is negotiatd. (WES)

LONGSHORE CURRENT — The resultantcurrent produced by waves being deflectedat an angle by the shore. In this case thecurrent runs roughly parallel to the shor~line. The longshore current is capable of

82

carrying a certain amount of material de-pending upon ita velocity and the particlesize of the material; however, any obstruc-tion, such as a submarine rock ridge or a ●land mint cutting across the path of thecurrent will cause loss of velocity and con-sequent Ioas of carrying power. (NOO)

LOUDNESS, n.— The intensive attribute ofan auditory sensation, in terms of whichsounds may be ordered on a scale extend-ing from soft to loud. Loudness dependsprimarily upon the sound pressure of thestimulus, but it also depends upon the fre-quency and wave form of the stimulus.(ASA)

LOUDNESS CONTOUR — A curve thatshows the related values of sound pressurelevel and frequency required to produce agiven loudness sensation for the typical lis-te~er. (ASA)

LOW, n. —.—In metrology, elliptical for“area of low pressure,” referring to a min-imum of atmospheric pressure in two di-mensions (closed isobars ) on a constant-height chart or a minimum of height (closedcontours) on a constant-pressure chart.Since a low is, on a synoptic chart, always

●-iated with cyclonic circulation, theterm is used interchangeably with CY-CLONE. (AMS)

LUMINESCENCE, n.— Emission of lightother than incandescence: Emission as a re-sult of and only during absorption of radi-ation from some other source is called@07escence. (ND)*

LUMINOUS EFFICIENCY — For a givenwavelength of visible radiation, the ratioof the flux that is effectively s%ed by thehuman eye to the flux that is intrinsic inthe radiation. Also called luminosity.(AMS)*

LUNAR TIDE — That pertion of a tide whichis due to the tide-producing force of themoon. (AMS)

LYSIMETER — 1. A device for measuringpercolation and leaching losses from a col-


umn of soil under controlled conditions.(SSS) 2. A device for measuring gains(precipitation and condensation) and losses(evapotranspiration) bya column of soil.(sss)

M

MACKEREL SKY — An area of sky with aformation of rounded and isolated cirro-cumulus or altocumulus clouds resemblingthe pattern of scales on the back of amackerel. (ND )

MAGMA, n.— Hot mobile rock materialgenerated within the earth, from whichigneous rock results by cooling and crys-tallization. It is usually conceived of as apasty or liquid material, or a mush of crys-tals together with a noteworthy amountof liquid phase having the composition ofsilicate melt. (S&V)

MAGNETIC FIELD — Any space or regionin which magnetic forces are present, as inthe earth’s magnetic field, or in or abouta magnet, or in or about an electric current.(AF)

MAGNETIC VARIATION — The angulardifference between magnetic north andtrue north, as in the “magnetic variationof X is 5° east.” AISO sometimes calledmagnetic decliruztiw. Magnetic variationis preferred over magnetic declination toavoid confusion with declinat~n as usedin astronomy. (AFD) ●

MANGROVE, n.— One of a group of halo-phytic evergreen broadleaf trees andshrubs of tropical and subtropical coasts,typically growing in muddy areas, such aslagoons and estuaries, that are submergedperennially or at high tide by brackish orsalty water. Many species of mangrovehave prop roots or root knees ahove theground.

MANOMETER, n.— An instrument formeasuring differences of pressure. Theweight of a column of liquid enclosed in a


tube is balanced by the pressure appliedat its opposite ends, and the pressure dif-ference is computed from the hydrostaticequation. A MERCURY BAROMETER isa type of manometer.

MANTLE ROCK — The unconsolidated ma-terial lying upon and in most cases derivedfrom the bedrock; REGOLITH, (S&V)

MAP CHART — A representation of a land-sea area, using the characteristics of a mapto represent the land area and the charac-teristics of a chart to represent the seaarea, with such special characteristics asto make the map chart most useful in mili-ati operations, particularly amphibiousoperations. (JD)

MARGINAL SEA ICE ZONE — The bandof sea ice from the ice edge to 75 milesinside pack ice under which any submar-ine can operate with a minimum of specialsonar equipment. (Upward-beamed echosounders are sufficient to allow surfacingin lakes. ) (IG)

MARINE BORER — A marine organismwhich attacks submerged or floating woodstruct~res in salt or brackish waters. The,two general groups recognized are thecrustaceans and molluscan borers. (SAF)

MARITIME AIR — A type of air whosecharacteristics are developed over an ex-tensive water surface and which, there-fore, has the basic maritime quality ofhigh moisture content in at least its lowerlevels. (AMS)

MARL, n.— Soft and unconsolidated cal-cium carbonate, usually mixed with vary-ing amounts of clay or other impurities.(sss)

MARSH, n.— 1. In general, any area of con-tinuously saturated or spongy ground hav-ing poor drainage, hence synonymous withSWAMP. (ADT) 2. In botany, an open,treeless, meadowlike or tussocky, salt orfresh-water tract of wet or spongy land,usually with occasional open, shallow poolsof water, and with a vegetation of more or

83


M] L-STO-l 16525 MARCH 1968

less dense, erect, aquatic or amphibiousplants including cattails, grasses, sedges,reeds, rushes, or other succulent herbs.(ADT)

MASS, n.- In shock and vibration termi-nology, a rigid body whose acceleration,according to Newton’s second law, is pro-portional to the resultant of all forces act-ing upon it.

MASSIF, n.— 1. A principal mountain mass.(S&V) 2. A block of the earth’s crustbounded by faults or flexures and dis-placed as a unit without internal change;a large fault block of mountainous topog-raphy. An intrusive body of moderate size;a diameter of between 10 and 20 milesmay be regarded as typical. The term doesnot imply any opinion on the mode “offormation or emplacement of that mass.(s&v)“

MASS MOVEMENT — A general term fora variety of processes by which largemasses of earth material are moved bygravity either slowly or quickly from oneplace to another. The rapid translocationof material in avalanches, landslides, andrelated events is one phase of mass move-ment but the slower, less noticeable actionsof earth flowage, soil-creep, and solifluc-tion probably accomplish greater effects.(s&v) ●

MATURE SOIL — Pedology. Any soil withwell-developed soil horizons having charac-teristics produced by the natural processesof soil formation and in near equilibriumwith its present environment. (SSS)

MAXIMUM THERMOMETER — A ther-mometer in which the mercury, or the in-dicator used for registering ‘temperature,remains at the higliest point reached sinceits last setting. (AD)

“MAXIMUM WATER-HOLDING CAPACI-TY — The average moisture content of ‘adisturbed sample of soil, one centimeterhigh, which is at equilibrium with a watertable at its lower surface. (SSS)

MEANDER, n.— One of a series of some-what regular winding or loopiirg bends ina stream. (GS) *

MEAN ANNUAL RANGE OF TEMPERA-TURE — The difference between the abso-lute maximum and minimum temperaturesfor a year, averaged over a given numberof years.

MEAN DAILY MAXIMUM (MINIMUM)TEMPERATURE — Average of the max-imum (minimum) temperatures for eachday within a given period, usually a month,over a period of years.

MEAN HOURLY TEMPERATURE — Av-erage of the daily temperatures at a givenhour for an indicated period, generally amonth, averaged oi,er a period of years.

MEAN MONTHLY CLOUDINESS — Aver-age of the mean cloud cover of each daywithin a month, averaged o~rer a period of .years.

MEAN MONTHLY DEWPOINT-Averageof the mean dewpoints of each day (gen-erally computed from observations takenat equal time periods of 6 hours or lessapart) within a month, averaged over aperiod of years.

MEAN MONTHLY MAXIMUM (MINI-MUM) TEMPERATURE — The highest(lowest) temperature for a month, aver-aged over a period of years.

LMEAN MONTHLY RELATIVE HUMIDI-TY — Average of the mean relative hu-midities for each day o’f‘the month, a\rer-aged over a period of years.

MEAN MONTHLY TEMPERATURE-Av-erage of the mean temperatures of eachday within a month, averaged over a per-iod of years. Some weather services requirethat a prescribed length of record be avail-able before “mean” is used.

iMEAJN RADIA.NT TEMPER.4TURE-Thetemperature at \vhich an object, gives outas much radiation as it receives from itssurroundings. In a room it is approximate-

84

. .


m ly the mean temperature of the walls,floor, and ceiling. (AMS)

MEAN SEA LEVEL — The average heightof the surface of the sea for all stages ofthe tide, used as a reference for elevations,(JD)

MEAN SOLAR DAY — The duration of onerotation of the earth on its axis, with re-spect to the mean sun. The length of themean solar day is 24 hours of mean solartime or 24 hours 03 minutes 56,555 secondsof mean sidereal time. A mean solar daybeginning at midnight is called a civil day;and one beginning at noon, 12 hours later,is called an astronomical G!ZZV.(ND)

MECHANICAL-ACOUSTICAL COUPLING— The interconnection of mechanical andacoustical elements. An example would bethe production of noise by mechanicalvibration of a gear casing.

MECHANICAL ANALYSIS — See PAR-TICLE-SIZE ANALYSIS.

‘a

MECHANICAL SHOCK — Sudden changesof excitation that develop significant in-ternal forces in a system. Mechanical shockexists when an applied force is suddenlychanged so ae to excite mechanical transi-ence in a system. (1S0)

MEDIUM-SCALE MAP — A map having ascale larger than 1:600,000 and smallerthan 1:75,000. (JD)

MELTING POINT — The temperature atwhich a solid substance undergoes FU-SION, i.e., melts, changes from solid toliquid form. The melting point of a sub-stance should be considered a property ofits crystalline form only. (AMS) *

MERCURY BAROMETER (or MERCUR.IAL BAROMETER) ——A glass instru-ment, employing mercury in its verticalcolumn, which is used to measure atmos-pheric pressure. (AMS ) *

MESA, n. — A flat-topped mountain boundedon at least one side by a steep cliff; a pla-teau terminating on one or more sides in

MiL-STD-l 16525 MARCH1968

a steep cliff; a tsbleland. (GS)

MESOCLIMATE, n.— The climate of smallareas of the earth’s surface which may notbe representative of the general climateof the district. (AMS) *

MESOCLIMATOLOGY, n.— The study ofMESOCLIMATES: the climatology of re-latively small areas which may not beclimatically representative of the generalregion. The data used in mesoclimatologyare mostly standard observations. The sizeof the area involved is rather indefiniteand may include topographic or landscapefeatures from a few scres to a few squaremiles, such as a small valley, a forest clear-ing, a beach, a village site. (AMS )

METAL FATIGUE — A weakening in thestrength of a metal cawed by repeated orfluctuating stresses. (AFD)

METAMORPHIC ROCKS — One of thethree great groups of rocks. Metamorphicrocks are formed from original igneousor sedimentary rockg through alterationsproduced hy pressure, heat, or the infil-tration of other materials at depths belowthe surface zones of weathering andcementation. (S&V)”

METEOR, n .— 1. Commonly, the streak oflight observed when a nwteoroid (a bodyfrom space) enters the earth’s atmosphere.2. Meteorot. A phenomenon observed in theatmosphere or on the surface of the earth,which consists of a precipitation, a suspen-sion or a deposit of aqueous or non-aqueousliquid or solid particles, or a phenomenonof the nature of an optical or electri-cal manifestation. See HYDROMETER.(WMO) ●

Note: The WMO definition arbitrarily ax.chdes clouds, here considered as a type ofmeteor.

METEORITE, n.— That portion of a rela-tively large body from space (a meteoroid)which survives its passage through theatmosphere and reaches the earth’s sur-face. (AMS) *

85



METEOROLOGICAL CHECK POINT—Arbitrarily selected point for which me-teorological corrections are determined asa timesaving expedient. These correctionsare applied to any target located withintransfer limits of the meteorological checkpoint. (AD)

METEOROLOGICAL DATA —Meteorological facts pertaining to the atmosphere,such as wind, temperature, air density andother phenomena which affect militaryoperations. (JD)

METEOROLOGY, n. —The study dealingwith the phenomena of the atmosphere.This includes not only the physics, chem-istry, and dynamics of the atmosphere, butis extended to include many of the directeffecti of the atmosphere upon the earth’ssurface, the oceans, and life in general.The goals often ascribed to meteorologyare the complete understanding, accurateprediction, and artificial control of atmos-pheric phenomena. (AMS)*

MICROBAR (or DYNE PER SQUARECENTIMETER)— A unit of pressurecommonly used in ACOUSTICS. One mi-crobar is equal to one dyne per squarecentimeter. See BAR and MILLIBAR.(ASA)

Note: The ternr “bar” denotes a pre,sureof 10” dynes par square centimeter. Unfor.tumately, the bar was once used in acousticsto mean one dyne per square centimeter. Itis recommended, therefore, in respect tosound pressure that the less ambiguousterms “microbar” or “dyne per square cm.timeter” be used. (ASA)

MICROBIOLOGICAL DETERIORATION—Physical destruction or functional dis.turbance of materials or equipment causedby the biochemical action of microbiology.ical agents such as fungi and bacteria.

MICROCLIMATE, n.— The tine climaticstructure of the air space which extendsfrom the very surface of the earth to aheight where the effects of the immediatecharacter of the underlying surface no

longer can be distinguished from the gen-eral local climate (mesocl imate or micro-climate). (AkfS) *

MICROCLIMATOLOGY, n. — The study ofMICROCLIMATE. It includes the studyof profiles of temperature, moisture andwind in the lowest stratum of air, theeffect of the vegetation and of shelterbelts,and the effect of towns and buildings inmodifying the microclimate. (AMS) ●

MICROMETEOROLOGY – That portion ofthe science of IMETEOROLOGY thatdeals with the observation andexplanation of the smallest-scale physicaland dynsmic occurrences within the atmo-sphere. So far, studies in this field areconfined to the surface boundary layer ofthe atmosphere; that is, from the earth’ssurface to an altitude where the effects ofthe immediate underlying surface upon airmotion snd composition become neglig-ible. (AIMS)*

MI CRORELIEF, n — Small-scaled differ-ences in relief, such as small mounts,swales, or pits that are a few feet acrossand have differences in elevation of a fewinches to around three feet that are signi-ficant to soil-forming processes, to growthof plants, or to preparing the soil forcultivation. (YA)

MICROWAVE, n.— A very short radiowave, usually shorter than one meter. Awave shorter than 10 meters long is calledan uttra-skort wave. ( ND)

MILDEW, n.— Any fungus growth whichmay be unsightly but which is not usuallyaccompanied by severe degradation of thesubstrate (material) upon which it isgrowing.

MILITARY GEOGRAPHIC DOCUMENTA-TION — Military geographic informationwhich has ‘been evaluated, processed, sum-marized and published. (JD)

MILITARY GEOGRAPHIC II’JJORMA-TION — Comprises the information con-cerning physical aspects, resources, andartificial features which is necessary for

86


MlL-STD-l 165

planning and operations. (JD)

MILITARY GEOGRAPHY – The specializedfield of geography cleating with natural andman-made physical features that may affectthe planning and conduct of militaryoperations. (JD)

MILLIBAR, n.— A unit of pressure equalto 1,000 dynea per square centimeter, or1/1,000 of a BAR. The millibar is used aaa unit of measure of atmospheric pressure,a standard pressure, a standard atmos-phere being equal to 1,013.25 millibars or22.92 inches of mercury. (ND)

MINERAL, n.— A substance occurring ininorganic nature, though not necessarilyof inoWanic origin, which has (1) a clef.inite chemical composition or, more tom.mordy, a characteristic range of chemicalcomposition, and (2) distinctive physicalproperties or molecular structure. (S&V) ●

MINERALIZATION, n.— 1. Geology. Theprnceas or the result of an induced changein a body of rrxk that results in (a) a massof economic value, (b) a mass of potentialeconomic value, or (c) massea of rock thatare related to (a) and (b) in origin.(S&V) 2. Pedology. The conversion of anelement from an organic form to an inor-ganic state as a result of microbial decom.position. (SSS)

MINIMUM THERMOMETER — A ther-mometer which automatically registers thelowest temperature occurring since its lastsetting. (ND)

MIRAGE, n.— A refraction phenomenonwherein an image of some object is madeto appear displaced from ita true position.Simple mirages may be any one of threetypes, the infer%w mirage, the s-aperior mir-age, or the futeral mirage, depending, re-s~tively, On whether the spurious imageappeara below, above, or to one side of thetrue position of the object. (AMS) *

MIRE, n.— 1. A small muddy marah or bog.(GS) 2. Wet spongy earth. (GS) ‘3. Softdeep mud. (GS)

87

25 MARCH1968

MIST, n.— 1. According to international def-inition: a HYDROMETER consisting ofan aggregate of microscopic and more-or-1sss HYDROSCOPIC water droplets sus-pended in the atmosphere. It produces, gen-erklly, a thin grayish veil over the land-scape. It reduces visibility to a lesser axtentthan FOG. REIATIVE HUMIDITY withmist is often leas than 95 percent. Mlat iaintermediate in all respects between HAZEand fog. 2. In popular usage in the UnitedStates, same as DRIZZLE. (AMS)”

MIXING RATIO — In a eystem of moist air,the dimensionless ratio of the maaa of watervapor to the mass of dry air. For many pur-poses, the mixing ratio may be approxi-mated by the SPECIFIC HUMIDITY.(AMS) ●

MOBILITY, n.— A qupfity or capability ofmilitary forces which pernrita them h movefrom place to place while retaking theability to fulfill their primary miamion.(JD)

MOBILITY, MECHANICAL — ‘l’be ratio ofa velncity-like quantity to a forcdike quan-tity when the argumenta of the real (orimaginary) parts of the quantities increaselinearly with time. The reciprocal of IM-PEDANCE, MECHANICAL. (SVH)

MOCK FOG — A simulation of true fog byatmospheric refraction. (ND)

MOCKUP — A mass used to simulate a pieceof equipment, having the same weight, cen-ter-of-gravity location, radii of gyration,and mounting means se a real or possiblepiece of equipment.

MODEL ATMOSPHERE — Any tbeoretiealrepresentation of the atmosphere, particu-larly of vertical temperature dlatribution.(AMS)

MODES, COUPLED — MODES OF VIBRA-TION that are not independent but whichinfluence one another becnuse of energytranafer from one mode to the other. (SVH)

MODE OF VIBRATION — A characteristicpattern assumed by a system undergoingvibration in which the motion of every


MlL-ST&l 16525 MARCH 1968

particle is simple harmonic with the samefrequency. (SVH)

MODE OF VIBRATION, NORMAL — AMODE OF VIBRATION that is uncoupledfrom (i.e., can exist independently of)other modes of vibration of a system.(SVH)

MODE, RESONANT — A MODE OF VI-BRATION in which a condition of RESO-NANCE exists. (SVH)

MODE, UNCOUPLED — See MODE OFVIBRATION, NORMAL.

MODULATION, n.— 1. The process by whichthe amplitude, frequency, or phase of acarrier wave is modified in accordance withthe character of a sigiial. 2. The variationin the value of some parameter which char-acterizes a periodic oscillation. (SVH )

MODULATION, AMPLITUDE — A type ofmodulation in which the amplitude of acontinuous carrier wave is varied in ac-cordance with properties of a second, ormodulating, wave. (AMS)

MODULATION, FREQUENCY — A type ofmodulation in which the frequency of acontinuous carrier wave is varied in ac-cordance with the properties of a second(modulating) wave. (AMS)”

MODULATION, PHASE — A type of MOD-ULATION in which the phase of the car-rier wave is varied in accordance with theproperties of a second, or modulatirig,wave.

MODULUS OF ELASTICITY — The ratioof stress to corresponding strain below theproportional limit. (S&V)

MOISTURE CONTENT — Soil Mechani&.The water content of a soil expressed as apercentage of the dry weight of the soil.The weight of the water is determined bydifferential weighings before and afteroven-drying a sample (BR)

MOISTURE EQUIVALENT — The weightpercentage of water retained by a previ-

ously saturated sample of soil one centi-meter in thickness after it has been sub-jected to a centrifugal force of one thou-sand times gravity for 30 minutes. (SSS)

MOISTUREPROOF, adj. — Able to resisttransmission of water vapor.

MONITORING, n.— 1. The act of detectingthe presence of radiation and the measure-ment thereof with radiation measuringinstruments. (JD) 2. The act of observingand recording laboratory and field environ-ment test conditions, test specimen re-sponses, and performance parameters.

MONSOON, n.— A name for seasonal winds(derived from Arabic mausim, a season).It was first applied to the winds over theArabian Sea, which blow for six monthsfrom northeast and for six months fromsouthwest, but it has, been extended tosimilar winds in other parts of the world.The primary cause is the much greaterannual variation of temperature over largeland areas compared with neighboringocean surfaces, causing an excess of pres-sure over the continents in winter and adeficit in summer, but other factors suchas the relief features of the land have aconsiderable effect. In India the term ispopularly applied chiefly to the southwestmonsoon and, by extension, to the rainswhich it brings. (A.MS) *

MONSOON FOREST — Partially or whollydeciduous forest in a tropical region whererainy seasolis alternate with long dry sea-sons, the trees being more or less leaflessduring the dry season. Monsoon forestsare rich in woody \inelike plants, but thetrees are not as large as in rainforests.

MORAINE, n. — Any accumulation of loosematerial deposited by a glacier. (GS)

MORASS, n. — A swamp, marsh, or bog hav-ing rank vegetation and muddy or offen-sive appearance. (GS)

MOTTLED, adj. — Pcdology. Soil horizonsirregularly marked with spots of color. Acommon cause of mottling is imperfect or

88


,*impeded drainage although there are otherG+UseS,such ss soil development from anunevenly weathered rock. Different kindsof minerals may cause mottling. (YA)

MOUNTAIN AND VALLEY WINDS — Asystem of diurnal winds along the axis ofa valley, blowing uphill and upvalley byday, and downhill and downvalley bynight; they prevail mostly in calm, clearweather. The upvalley component or valleywind is due to the temperature differencebetween the air heated over the slopes andthat at the same height in the free air. Thedownvalley component or mountain windat night is due to nocturnal cooling and issomewhat weaker, up to 9 mph. ( AMS) *

MOUNTING BASE — A mounting systemfor the support of a piece of equipmentand for its protection against shock andvibration. It consists of hardware and faa-tening devices for attachment to the pieceof equipment and to the vehicle structure,and resilient members and media, if used.

● MOUTH, n.— The place of discharge of astream into the ocean or entrance to a bayfrom the ocean. (NOO),’

MUCK, n.— Highly decomposed organic soilmaterial developed from PEAT. Gener.ally, muck has a higher mineral or aahcontent than peat and is decomposed tothe point that the original plant parta can-not be identified. (YA)

MUD, n.— A slimy, sticky mixture of waterand finely divided particles of a solid suchas dirt, having little or no plasticity. (ND)

, MUDFLOW, n.— A well-mixed mass ofwater and alluvium which, because of itshigh viscosity and low fluidity as comparedwith water, moves at a much slower rate,usually piling up and spreading over thefan like a sheet of wet mortar or concrete.(MH)

MULL, n.— Pedolog#. A humus-rich layerof forested soils consisting of mixed organicand mineral matter. A mull blends into the

●uPPer mineral-laws without an abrupt

89

MlL-STD-l 165!25 MARCH 1968

change in soil characteristics. (YA)

MULTIPLE DEGREELOF-FREEDOM SYS-TEM — In shock and vibration terrninol-o~ a sYstem for which two or more Cwr.dmatea are required ti define completelythe configuration of the system at any in-stant. (SVH)

MUNSON TEST COUURSE — An extensivenet work of automotive test courses laid outat Aberdeen Proving Ground, Maryland.Each of the test courses has been engi-neered based on a specific requirement fortest operation. The course covers the fol-lowing: amphibious lands, rolling hills,mud, slopes (30° left and right), wash-board, straightaway, imbedded rock, ford-ing, wave course, soil dynamometer, cob-blestone, bowl, staggered bump, corduroy,loose rock,. shell hole, bridging device, ver-tical wall, gravel road, turning circles,slope grade of 5, 10, 15, 20, 30, 40, 50 and60 percent, and Belgian block.

MUSKEG, n. — That terrain which is madeup’of a living organic mat of mosses, sedgeaor grasses (with or without tree growth)underlain by an extremely compressiblemixture of partly disintegrated and decom-posed organic material. (NRCC)

N

NADIR, n.— That point on the celestialsphere directly beneath the observer anddirectly opposite the zenith. (AF)

NARROW(S), n. — (Usually used in theplural. ) 1. The contracted part of a stream,lake, or sea. (GS) 2. A strait connectingtwo iwdies of water. (GS)

NATURAL ENVIRONMENT — That partof the total environment which comprisesthe complex of conditions found in nature.The term ia looaelv used for an environ-ment dominated ~y natural ENVIRON-MENTAL FACTORS.



NAUTICAL MILE — A measure of distanceequal to one minute of arc on the earth’ssurface.. The United States has adopted, theInternationalN autical Mile equal to 1,852meters or 6,076.11549 feet. (JD) It isequivalent to.1.1508 statute miles.

NAUTICAL TWILIGHT (MORNING ANDEVENING) —That period during whichthe sun travels from a position”12 degreesbelow the horizon to its position.at sun-rise; that period during which the suntravels from its position at sunset to aposition 12 degrees below the horizon. Thisis a period when general outlines may bevisible, although the horizon probably can-not be distinguished. (AD)

NECK, n.—l. A narrow strip of land con-necting twolarger areasora narrow Lmdyor channel of water between two largerbodies of water. (S&V) 2. The narrowband of water flowing swiftly seawardthrough the surf. (NOO)

NETTLE, n.—l. Any of a genus of plants( flrtica), chiefly coarse herbs, armed withstinging hairs. 2. Loosely, any prickly orstinging plants.

NEUTRAL SOIL — Pedokgy. A soil that isneither significantly acid nor alkaline.Strictly, a neutral soil has PH of 7.0; inpractice, a neutral soil has a pH between6.6 and 7.3. (YA)

NEUTRALIZE, v.t. — To make harmlessanything contaminated with a chemicalagent. (AD )

NEUTRON INDUCED ACTIVITY — Ra-dioactivity. induced in the ground or anobject as a result of direct irradiation byneutrons. (JD)

NEWTON (Abbreviated N), n.— A unit offorce in the International System of Units(S1) ; a force which, when applied to abody having a mass of one kilogram, givesthe body an acceleration of one meter pereecond per second. One newton is equival-ent to 10fidynes.

NIVATION, n. – Erosion behind and perip-heral to a snowbank, caused by frost action,mass movement, transport by melt water,or other related processes. Nivation is mostnoticeable behind summer snowbankswhen nightly freezing alternates with day-time melting. (ADT)

NOISE, n.— 1. Any undesired sound. Byextension, noise is any unwanted disturb-ance ‘within a useful frequency band, suchas undesired electric waves in a transmis-sion channel or device. (ASA) 2. Anerrratic, intermittent, or statistically ran.dom oscillation (ASA)

NOISE, ‘AMBIENT — The all-encompass-ing noise associated with a given environ-ment, being usually a composite of soundsfrom many sources near and far. (ASA)

NOISE, AUDIBLE—See AUDIBLESOUND.

NOISE, BACKGROUND — The total of allsources of interference in a system usedfor the production, detection, measure-ment, or recording of a signal.

Note 1: Ambient noise detected, measured,or recorded with the signal becomes partof the background noise..Votc2: Included in this definition is the in-terference resulting from primary powersupplies, that separately is commonly de-scribed as hum. (ASA)

NOISE LEVEL — 1. The level of noise, thetype of which must be indicated by furthermodifier or context.

.Vofe: The physical quantity measured(e.g., voltage), the reference quantity, theinstrument used, and the band-width orother weighting characteristic must be in.dicated. (ASA)

2, For air-borne sound, unless specified tothe contrary, noise level is the weightedsound pressure level called sound level; theweighting must be indicated. (ASA)

NOISE, RANDOM — An oscillation whoseinstantaneous magnitude is not specified

90


,,.

\


● for any given instant of time. The instan-taneous magnitudes of a ~andom noise arespecified only by probabd ity distributionfunctions given the fraction of the totaltime that the magnitude, or some sequenceof magnitudes, lies within a specified range.(ASA) *

NOISE, THERMAL — 1. Random noise ina circuit associated with the thermodynamicinterchange of energy necessary to main-tain thermal equilibrium between the cir-cuit and its surroundings. 2. The noise pro-duced by thermal agitation of charges in aconductor. Also called Johnson Noise.

NOISE, WHITE — A noise whose spectrumdensity (or spectrum level) is substantiallyindependent of frequency over a specifiedrange. White noise need not be random.(ASA) *

NORMAL, n. Chrdot.- An average basedon a standardized period of record, e.g. a30-year normal.

● NORMAL IMPACT — Striking of a projec-tile against a surface that is perpendicularto the line of flight of the projectile. (AD)

NORMAL SOIL — Pedolog#. A soil having aprofile in near equilibrium with its environ-ment; developed under good but not ex-cessive drainage from parent material ofmixed mineral, physical, and chemicalcomposition. In its characteristics it ex-preeees the full effects of the forces ofclimate and living matter. (YA)

NORTHERN OPERATIONS — Northernoperations include hth Arctic and Sub-arctic. The terms cold weather operations,operations in the northern latitudes, andnorthern operations are all synonymousand for purposes of definition are com-bined under the all-inclusive term northernoperations. (AD) See also AREA OFNORTHERN OPERATIONS.

NUCLEAR AIRBURST — The explosion ofa nuclear weapon in the air, at a height

●greater than the maximum radiue of the

91

fireball. (JD) I

~~ INUCLEAR CLOUD — An all inclusive term

for the volume of hot gases, smoke, d~stand other particulate matter from, the n=-clear bomb itself and from its environ-ment, which is carried aloft in conjunc-tion with the rise of the fireball producedby the detonation of the nuclear weapon.(JD)

NUCLEAR SURFACE BURST — An explo-sion of a nuclear weapon at the surface ofland or water; or above the surface, at aheight less than the maximum radius ofthe fireball. (JD)

NUCLEAR UNDERGROUND BURST —The explosion of a nuclear weapon inwhich the center of the detonation lies ata point beneath the surface of the ground.(JD)

NUCLEAR UNDERWATER BURST—Theexplosion of a nuclear weapon in whichthe center of the detonation lies at a pointbeneath the surface of the water. (JD)

NUCLEAR YIELDS - The energy released inthe detonation of a nuclear weapon, meas-ured in terms of the kilotons or megatonsof trinitrotoluene (TNT) required to pro-duce the same energy release. Yields arecategorized as:

Very low .................... less than 1 kilotonLow ................... 1 kiloton to 10 kilotonsMedium ................ over 10 kilotons to 50

kilotonsHigh .................... over 50 kilotons to 500

kilotonsVery high .................... over 500 kilotons

NUCLEATION, n.— Any process by whichthe phase change of a substance to a morecondensed state (CONDENSATION, SUB-LIMATION, FREEZING) is initiated atcertain loci (see NUCLEUS) within theless condensed state. (AMS)

NUCLEUS, n. – 1. An agent of NUCLEA-TION. 2. In physical meteorology, a psrti-cle of any nature upon which, or the locus



locus at which, molecules of water or ice boundaries, the chemistry and physics ofaccumulate as a result of a phase change sea water, and marine biology. 2: In strictto a more condensed state. (AMS) 3. In usage oceanography is the description ofnuclear technology, the positively charged the marine environment, whereas oceano?- ●core of an atom. with rmactically the whole ogu is the study of the oceans and relatedmass of the atom bit occupy-ing only a . sc;ences. (NOO”)minute part of its tiolume.

NUNATAK, n.— In glacial geology, an iso-lated hill or peak which projects throughthe surface of a glacier, or which was for-merly surrounded but not covered byglacial ice. (ADT)

o

OASIS, n.— An isolated area within a DES-ERT, with GROUND WATER at or nearthe surface, resulting in a fertile or greenspot, varying in size from a small groveof palms to an area of over a hundredsquare miles. (GS ) *

OBSTACLE — A definable environmentalfeature that inhibits the movement of avehicle. (WES)

OCCLUDED FRONT — A composite of twoFRONTS, formed as a cold front overtakesa warm front or quasi-stationary front.This is a common process in the late stagesof wave-cyclone development, but is notlimited to occurrence within a wavecyclone. (AMS )”

OCCLUSION, n. – 1. Same as OCCLUDEDFRONT. (AMS) 2. In meteorology, theprocess of formation of an occluded front.(AMS)*

OCEAN CURRENT — A movement of oceanwater characterized by regularity, eitherof a cyclic nature, or more commonly asa continuous stream flowing along a“ de-finable path. (AMS) ●

OCEANOLOGY, n. —See OCEANOG-RAPHY

OCEANOGRAPHY, n. – 1. The study of thesea, embracing and integrating alf know-ledge pertaining to the sea’s physical

OCTAVE, n. — 1. The interval between twooscillations having a basic frequency ratioof two. (ASA)

OFF-ROAD, adj. — Away from terrain spe-cifically improved for vehicle use. (WES)

OFFSHORE BAR, n. — The narrow ridgeof sand deposited parallel to the shore inshallow water. Its accumulation is due tothe deposition of sand in the breaker zone.(s&v)”

OIL RESISTANCE — The ability of a ma-terial to withstand degradation by a speci-fied oil. Such degradation is usually char-acterized by swelling, softening, and lower-ing of mechanical properties.

OPEN IMPROVED STORAGE SPACE —Open area which has been graded and hardsurfaced or prepared with topping of somesuitable material so as to permit effective

ematerial handling operations. (JD)

OPEN UNIMPROVED WET SPACE —That water area specifically allotted to andusable for storage of floating equipment.(JD)

OPERATIONAL ENVIRONMENT — 1. kpertains to the military, it is a compositeof tbe conditions, circumstances, and in-fluences which affect the employment ofmilitary forces and which bear on thedecisions of the commander. (JD) 2. .@environment associated with the operationof a structure or equipment.

ORDER, n.— 1. Pedotogv. The highest cate-gory in soil classification. The three ordersare zonal soils, intnz:onal soils, and a:omz~soils. (YA) 2. A category in the classifica-tion of plants and animals, ranking belowthe ckzs.vand above the family.

ORGANIC SOIL — Perfology. A general


a term applied to a soil or to a soil horizonthat consists primarily of organic matter,such as peat soils, muck soils, and peaty soilIayers. (YA)*.

OROGRAPHIC PRECIPITATION — Preci-pitation which results from the lifting ofmoist air over an orographic barrier suchas a mountain range. Strictly, the amountse designated should not include that partof the precipitation, which would be ex-pected from the dynamics of the associatedweather disturbance, were the disturbanceover flat terrain. (AMS ) *

OSCILLATION, STABLE — An oscillationthat is either damped (i.e., continuallydecreasing in amplitude) or neutral (i.e.,maintains constant amplitude). (AMS ) *

OSCILLATION, UNSTABLE — Any oscil-lation which is not stable, i.e., an erratic,intermittent, non-self-sustaining oacilla.tion, or one which grows in magnitudeuntil it breaks down. (Definition not ac.cepted by Air Force.)

OSCILLATOR, n.— The general term foran electrical device which generates alter-nating currents or voltages. The oscillatoris classified according to the frequency ofthe generated signal. (AMS )

OSCILLOGRAPH, n.— A device for graph.ically recording or indicating oscillationsor changes in an electric current. (ND)

OSCILLOSCOPE, n.— An instrument forproducing a visual representation of oscil-lations or changes in an electric current.The face of the cathode ray tube used forthis representation is called a scope orscreen. (ND )

OUTCROP, n.— A part of a body of reckthat appears, bare and exposed, at theeurface of the ground. In a more generalsense the term applies also to areas wherethe rock formation occurs next beneaththe soil, even though it is not exposed.(s&v)

OUTLET, n.— 1. The lower end of a lake orpond. (GS) 2. The point at which a lake


or pond discharges into the stream whichdrains it. (GS)

OUTWASH, n.— 1. Stratified accumulationof water-deposited glacial drift (seeDRIFT, GLACIAL). The material is laiddown by the meltwater streams issuingfrom the face of the glacier ice. Usuallylaid out in nearly level plains. 2. Sometimesused to mean any water-deposited materialcarried and laid down by streams. (NAS)

OUTWASH PLAIN — A broad deposit ofdetrital material sloping gently away froma glacial terminus or terminal moraine.An outwash plain may merge downstreamwith the valley train. Alao called orhoashapron or outwa.sh fan. (ADT)

OVERLAND FLOW — The flow of rain-water or snowmelt over the land surfacetoward stream channels. After it enters astream, it becomes runoff. (MH)

OVERPACKAGING, n.— The use of more(quantitative or qualitative) preservation,packaging or packing materiala than isnecessary to protect an item adequately.This term should’ not be confused withOVERPACKING. (AD)

OVERPACKING, n.— Repacking of con-biners or items into more substantial andsuitable container to withstand ,handlingand transportation hazards, or the addi-tion of packing materials such as steelstrapping, waterproof caseliners, fiber-board sleeves onto fiberboard boxes, etc.,to render the existing container less sus-ceptible to damage or pilferage duringhandlin~, transportation and storage.(AD)

OVERPRESSURE, n.— The pressure re-sulting from the blast wave of an explos-ion. It is referred to as “poeitive” when itexceeds atmospheric pressure and “nega-tive” during the passage of the wave whenresulting pressures are less than atmoe-pberic pressure. (JD)

OXBOW, n. — 1. A river bend shaped likean oxbow with only a neck of land left

93



between two parta of the stream. (GS) 2.The crescent-shaped lake remaining in theabandoned channel after a river hasformed a cut-off and the ends of the orig-inal bend have been filled. (GS ) Also calledozbow lake.

OXIDATION, n.— 1. The change in a cornpound caused by an increase, in the propor-tion of the electronegative part or thechange of an element or an ion from alower to a higher positive vaience. 2. Lossof electrons by a constituent of a chemicalreaction. ( ECS )

OXIDATION, INTERNAL — The precipita-tion of one or more oxides of alloying ele-ments beneath the external surface of analloy as a result of oxygen diffusing intothe alloy from an external source.

OZONE, n. — A form of molecular oxygen,each molecule consisting of three atoms.Ozone has a characteristically pungentodor. It is formed by electrical discharge inair, but in the upper atmosphere is believedto be produced by the effect of ultravioletradiation from the sun on oxygen. (ND)

P

PACKAGING, n.— Application or use ofappropriate wrappings, cushioning, inte-rior containers and complete identificationmarking, up to but not including the exte-rior shipping container. (AD)

PACK ICE — Any area of sea ice other thanfast ice composed of a heterogeneous mix-ture of size and age types. Pack ice is usu-ally in motion and is often referred to asdr-i~t ice. The concentration of pack ice canbe of any degree. (IG)

PACKING, n.— Application or use of exte-rior shipping containers and assembling ofitems or packages therein, together withnecessary blocking, bracing, or cushioning,weatherproofing exterior, strapping andmarking of shipping containers. (AD)

PAHOEHOE, n. — Solidified lava that ischaracterized by a smooth, billowy, or ropysurface having a skin of glass a fractionof an inch to several inches thick. Pahoshoeia distinguished from the AA type by itssmooth surf ace. (S&V ) *

PALLOGRAPH, n. — A low frequency VI-BROGRAPH. (SVH)

PANCAKE ICE — Pieces of newly formedice, usually approximately circular, withraised rims and from 1 to 6 feet in diam-eter. ( IG)

PARTIAL NODE — The point, line, or sur-face in a STANDING.WAVE RESONANTSYSTEM where some characteristic of thewave field has a minimum amplitude differ.ing from zero. The appropriate modifiershould be used with the words “partialnode” to signify the type that is intended;e.g., displacement, velocity, partial pres-sure, etc. (SVH)

PARTICLE-SIZE ANALYSIS — Soil J’fe-chanics, Determination of the variousamounts of the different separates in a soilsample, usually by sedimentation, sieving,micrometry, or combinations of thesemethods. Formerly termed mechanical an-Ulyw”s. (sss) “

PARTING, n. — 1. Metallurgy. The wlectivecorrosion of one or more components of asolid solution alloy. (ECS) 2. Geology. Athin depositional layer separating thick de-posits, se shale in a coal seam; also a jointor fissure. (S&V)

PARTING LIMIT — The maximum concen-tration of a more noble component in analloy, above which PARTING does not oc-cur within a specific environment. (ECS)

PASS, n.— 1. A break in a mountain range,permitting easier passage from one side ofthe range to the other. Also called a cot.(ND) 2. A narrow connecting channel be.tween two bodies of water; also the inletthrough a barrier reef atoll or sand bar ora navigable channel at a river’s mouth.(NOO)

94

.,.



PASSIVE, adj. — A metal or alloy is passiveif it substantially resists corrosion in anenvironment where thermodynamicallythere is a large free energy decrease as-sociated with its paesage from the metallicstate to appropriate corrosion products.(ECS)

PATINA, n.— 1. A green coating consistingprincipally of basic sulfate and occasional-ly containing small amounts of carbonateor chloride, which forms on the surface ofcopper or copper alloys exposed to the at-mosphere a long time. (ECS) 2. Same asDESERT VARNISH.

PATTERNED GROUND—A collective termfor ground surface patterns resulting fromfrost action; the surface expression of soilstructures. It is common but not exclusiveto PermafrOSt regions; it includes alarge group of soil forms which have dis-tinct linear or polygonal elemente in groundplan, such as stone rings, stone nets, andstone garlands.

PEAK LEVEL — The maximum instantane-ous level that occurs during a specifiedtime interval. In acoustics, peak ‘soundpressure level is to be understood, unlesssome other kind of level is specified. (ASA)

PEAT, n. -An acid, dark-colored, soft, usually coarsely fibrous, unconsolidated soilwith a 96 to 99 percent content of partlydecomposed, somewhat carbonated plantmaterial accumulated under conditions ofexcessive moisture. (ADT ) *

PEAT BOG— An area of soft, wet, spongyground, consisting chiefly of decayed or de-caying moss and other vegetable matter,where PEAT is formed. See QUAKINGBOG AND SWAMP.

PEA’S SOIL — An organic soil containingmore than 50 percent organic matter. Usedin the United States to refer to the stageof decomposition of the organic matter,peat referring to the slightly decomposedor undecomposed deposits and muck to thehighly decomposed materials. (SSS)

PEBBLE, n.— A small stone worn smoothby the action of water, ice, sand, etc., or anystone between 4 and 64 millimeters (about0.16 to 2.5 inches) in diameter. (ND)

PEDALFER, n.— Pedology. A soil in whichthere has been a shifting of alumina andiron oxide downward in the soil profile butwith no horizon of carbonate accumulation.(S&V) (The term is considered obsoleteby SSS.)

PEDOCAL, n.— Pedokwy. A soil with awell-developed horizon of accumulated cal-cium carbonate or, more rarely, some othercarbonate. (S&V ) (The term is consid-ered obsolete by SSS.)

PEDESTAL ROCK — A reeidual or erosion-al rock supported by a relatively slendercolumn or pedestal. (S&V)

PEDIMENT, n.— A gently inclined erosionsurface of low relief typically developed inafid or semiarid regions at the foot of areceding mountain slope. The pedimentmay be bare or mantled by a thin layer ofALLUVIUM which is in transit to the ad-joining basin. Some pediments resembleALLUVIAL FANS in outward form.(s&v)●

PERCOLATION, n, — The movement, underhydrostatic pressure, of water through theinterstices of a rock or soil, except themovement through large openings such ascaveg. (MH )

PERELETOK, n.— An isolated layer offrozen ground between the thawed part ofthe active layer and a talik, uwally lastingonly a season or two and formed whenever,owing to excessive winter cold or to sub-normal summer temperatures, the summerthaw does not completely melt the activelayer. (AD)

PERIOD, n.— 1. The time interval neededto complete a cycle. (ND) 2. The smallestincrement of the independent variable forwhich the function repeats itself. ( ISO)

PERMAFROST, n. 1. Permanently frozenground. (JD ) 2. A thickness of soil, super-

95


MlL-STD-l 16S25 MARCH J968

ficial deposit, or bedrock of variable depthbeneath the surface of the earth in whichbelow-freezing temperature has existedcontinuously for a lonz time. Also calledperennially” frozen ~round, pergel~ol.(ADT) ●

PERMAFROST ISLAND – An area ofperennially frozen ground surrounded byunfrozen ground. (ADT)

PERMAFROST, PASSIVE — Ground pe-rennially frozen under climatic conditionscolder than those now present, which willnot refreeze as permanently frozen groundwhen once disturbed. (ADT) *

PERMAFROST TABLE – The surface thatrepresents the upper boundary ofperennially frozen ground. Sometimescalled ~rost line. (ADT)

PERMAFROST ZONE — The aggregate ofregions in which permafrost occurs.(ADT)

PERMEABILITY, n.— The property orstate of being permeable, of allowing fluidsand gases to pass through. The standardcoefficient of permeability used in the hy.drologic work of the U. S. Geological Sur.vey is defined as the rate of flow of waterat 60”F, in gallons a day, through a crosssection of one square foot, under a hydrau-lic gradient of 100 percent (S&V)

pH — A numerical designation of relativelyweak acidity and alkalinity as in soils andother biological systems. Technically, pH isthe common logarithm of the reciprocal ofthe hydrogen-ion concentration of a solu-tion. .4 pH of 7.0 indicates precise neutral.ity, higher values indicate increasing alka-Iinity,and “Ibwer values indicate increasingacidity. See HYDROGEN ION CONCEN-TRATION. (YA)

PHASE, n.— 1. A measure of the stage ofprogress in the cycle of any periodic” mo-tion, usually expressed as a phase angle,one complete cycle representing a phaseangle of 360 degrees; e.g., a phase angleof 90 degrees indicates that the cycle is one.

quarter completed. 2. In a propagating sinewave (simple harmonic wave) points ofequal phase are separated by a distance ofone wavelength.

PHON, n.— The unit of loudness level of asound, defined as numerically equal to themedian sound pressure level, in decibels,relative to ,0.0002 microbar, of a free pro-gressive wave of frequency 1000 cycles persecond presented to listeners facing thesource, which in a number of trials iijudged by the listeners to be equally loud.(ASA)”

PHOSPHORESCENCE, n. — Emission oflight without sensible heat, particularly asa result of but continuing after absorptionof radiation from some other source.(ND)*

PHOTOGRAMMETRY, n.— 1. The art, sci-ence, or process of making maps and scaledrawings from photographs, especially ofmaking maps from aerial photographs.(AFD) 2. The process of making precisemeasurements by the use of photography.(AFD)

PHYSICAL METEOROLOGY — Thatbranch of meteorology which deals withoptical, electrical, acoustical, and the ther-modynamic phenomena of the atmosphere,its chemical composition, the laws of radi.ation, and the explanation of clouds andprecipitation. (AMS) ●

PICKLE, n.— A solution or process used toloosen or remove corrosion products suchas scale and tarnish from a metal. (ECS)

PICKLE, v, tr. — To loosen or remove cor-rosion products such as scale and tarnishfrom a metal.

PICKUP, n.— See TRANSDUCER.

PINGO, n. — A form of frost mound; specifi-cally, a large mound of ice covered withsoil. Pingos are not uncommonly 100 feetor more in height, and are persistent,prominent latidscape features. The crestmay be broken which allows mud to oozeout during a thaw. (ADT) *

96 a


MlL-STD-l 165

PIN-HOLING — A film defect characterizedbv the uresence of tiny holes. The term is.rather generally appli~d to holes caused bysolvent bubbling, moisture, other volatilepraducts, or the presence of extraneousparticles in the applied film.

PITCH, n.—l. That attribute of auditorysensation in terms of which sounds may beordered on a scale extending from low tohigh. Pitch depends primarily upon the fre-auenc~ of the sound stimulus. but it alsa~epends upon the sound pressure andwaveform of the stimulus. (ASA) 2. Os-cillation of a missile, airplane, or shipabout a lateral axis, e.g., the alternate ris-ing and falling of the bow and stern of aship. (AF)

PITOT TUBE — An instrument for measur-ing the relative speed of a fluid. It consistsof a concentric pipe arrangement in #hichthe inner pipe is open at one end and theouter pipe is perforated and closed at bothends; each pipe ia connected to a manome-ter. The unit is operated with the open endpointing upstream, so that the inner pipemeasures the total pressure and the outerpipe measures the static pressure. The dif-ference in these pressures, the d~micpressure, is proportional to the square ofthe fluid speed. (AMS)

PITOT-TUBE ANEMOMETER — A pres-sure-tube anemometer, consisting of aPitot tube mounted on the windward end afa wind vane and a suitable manometer tomeasure the developed pressure and cali-brated in units of wind speed. (AMS)

PITTING FACTOR—The depth of the deep-est pit resulting from corrosian divided bythe average penetration as calculated framweight loss. (ECS)

PLAIN, n.— A comparatively flat, smcdh,and level tract without noticeable hills,mountains, or valleys. To some geologiststhe notian of underlying horizontal strutture is essential to the definition, but mostwriters consider only the surface configu-ration. (S&V)

25 MARCH1968

PLANIMETRIC MAP — A map represent-ing only the horizontal position of fea-tures. Sometimes called a line map. (JD)

PLANE-WAVE TUBE — A type Of acousti-cal testing facility in which impingementof acoustic energy upon a test specimenis inherently unidirectional.

PLANKTON, n.— The passively floating orweakly swimming animal and plant life ofa body of water.

PLANOSOL, n.— Pedology. An intrazonalgraup of soils with eluviated surface hori-zons underlain by claypans or fragipans,developed on nearly flat or gently slopinguplands in humid or subhumid climates.(YA)

PLANT GROWTH REGULATOR—A chem-ical arrtiplant agent which regulates or in-hibits plant growth. (AD)

PLANT NUTRIENT — Any elerrwnt takenin by a plant, essential to its growth, andused by it in elaboration of its food andtissue. (YA)

PLASTIC LIMIT — Soil Mechanics. One ofthe measures of soil consistency (see AT-TERBERG LIMITS). The lowest moisturecontent, expressed as a percentage of theweight of the oven-dried soil, at which thesoil can be rolled into threads one-eighthinch in diameter without the thread break-ing into pieces. (S&V) *

PLASTICITY, n.— The property of a mate-rial that enables it to undergo permanentdefamation without elastic rebound, andwithout rupture. (S&V) *

PLASTICITY INDEX — The difference inthe water content of a soil at its LIQUIDLIMIT and at its PLASTIC LIMIT. Clayeysoils, for example, have higher plasticityindexes than non-clay soils, because theyremain plastic over a wider range of watercontent.

PLATEAU, n.— L A level on which little orno change takes place; a representation ofthis on a graph. Used especially of trends,

97



materiel requirements, learning process,etc. (AFD) 2. A tableland or flat-toppedarea of considerable extent elevated abovesurrounding country on at least one side.A plateau is larger and more extensivethan a MESA but the two cannot be strict-ly separated. The surface may be fairlysmooth but not necessarily so, large moun.tairr masses may rise above it, and deepcanyons may he cut into it. (S&V) *

PLATY SOIL STRUCTURE — Soil aggr~gates with thin vertical axes and long hori-zontal axes. Flat, tabular; a three-dimen-sional object that has one dimension muchsmaller than the other two. (YA )

PLAYA, n.— The flat or nearly flat, low partof an enclosed basin or temporary lakewithout outlet; also known as a dry fake.Includes dry, moist, crystal body, com-pound, LIME PAN, and artificial playae.

PLAYA LAKE — A lake occupying a playa.Such lakes are usually very shallow andtemporary in nature, (S&V)

PLUCKING, n.— The process by which rockfragments are detached from’ bedrock bythe movement of glacial ice. Also calledquamying. (ADT)

PLUTONIC ROCKS — See IGNEOUSROCKS.

PODZOL, n.— Pedology. A zonal group ofsoils having surface organic mats and thin,organic-mineral horizons above grayleached horizons that rest upon illuvialdark-brown horizons developed under co-niferous or mixed forests or under heathvegetation in a cool-temperate, moist cli-mate. (YA )

PODZOLIZATION, n. — Pedology. The proc-ess by which soils are depleted of bases,become more acid, and develop leached sur.face layers from which clay has been re-mdved. (YA)

POLAR AIR — In the Bergeron system ofair mass classification, air typical of thesubpolar high pressure areas. Abbreviatedas P.

.Note: Polar air in this u$age actuallymeans subpolar air, thus a polar air massusually originates fm-tber south than anarctic air mass. (ADT)

POLAR ICE — Extremely heavy sea ice upto ten feet or.more thick and of more thanone winter’s growth. Heavily hummocked,it may ultimately be reduced by weather-ing to a more or less even surface. ( IG )”

POLARIZATION, n.— The state of an elec-tromagnetic wave in which the electric(and magnetic) field vector vibrates in astraight line in the plane perpendlcuIar tothe direction of wave propagation (planepolarization) or rotates periodically, sweep-ing out an ellipse or circle in the perpen-dicular plane (eUipticat or eireufar pobzr--zation).

POLAR REGIONS — Those parts of theearth’s surface which have an average tem-perature of the warmest month of less than32 degrees Fahrenheit. (AD)

POLDER, n.— Land reclaimed from the seaor other body of water by the constructionof an embankment to restrain the water.(ND)

POLYGONAL SOIL — More or less regularsided ground surface patterns created byfrost action, by thawing or ground icewedges, or both. A widespread phenomenonover the permafrost area indicating poordrainage. (AD)

POLYNYA, n.—Any enclosed sea water areain pack ice, other than a le~d, not largeenough to be called open water-. In summerit may be referred to as a lake; in winterwith a covering of relatively thin ice itmay be called an ice skylite. (IG)

POND, n. — A relatively small body of water,usually surrounded on all sides by land. Alarger body of water is called a take. ( ND)

PONDAGE, n. —Small-scale storage at awaterpower plant to equalize daily or week-ly fluctuations in river-flow or to permitirregular hourly use of the water for po~vergeneration to accord with fluctuations inload. (MH)

9a



POOL, n.— 1. Any enclosed relatively smallsea area in pack ice or drift ice other thana lead or a land. (NOO)” 2. A small bodyof water, usually smaller than a pond, es-pecially one that is quite deep, One leftby an ebb tide is called a tide pool. (ND)3. A small and comparatively still, deeppart of a larger body of water such as ariver or harbor. (ND)

POROSITY, n.— The property of a rock ofcontaining intemtices without re~rd tosize, interconnection, or arrangement Ofopenings. It is expressed se percentage oftotal volume occupied by interstices. (S&V)

POROSITY, SOIL — The degree to whichthe soil mass is permeated with pores orCsvitiw. Porosity can be generally expressedas a percentage of the whole volume of asoil horizon that is unoccupied by solidparticles. J (YA) *

POTENTIAL EVAPOTRANSPIRATION—Water loss that will occur if at no timethere ia a deficiency of water in the soil foruse of vegetation. (MH)

POTENTIAL NATURAL WATER LOSS-The water loss during years when the an-nual precipitation greatly exceeds the aver-age water loss. It represents the approxi-mate upper limit to water loss under thetype and density of vegetation native to abasin, actual conditions of moisture sup-ply, and other baain characteristics where-as potential evapotranspiration representathe hypothetical condition of no deficiencyof water in the soil at any time for use ofthe type and density of vegetation thatwould develop. (MH)

POTENTIOMETER, n.—An instrument formeasuring differences in electric potential.Essentially, this instrument balancea theunknown voltage against a variable knownvoltage. Potentiometers are frequentlyused in conjunction with thermocouples formeasuring temperature. (AMS) *

POTHOLE, n.— A more or less circular holeformed in the rocky beds of rivers by thegrinding action of stones or gravel whirled

around by the water in a particular spot.(s&v)

POWER SPECTRAL DENSITY — The lim-iting mean-square value (e.g., of accelera-tion, velocity, displacement, stress, or otherrandom variable) per unit bandwidth; i.e.,the limit of the mean-square value in agiven rectangular bandwidth divided by thebandwidth, as the bandwidth approacheszero. (SVH )

POWER SPECTRAL DENSITY LEVEL —At a particular frequency, the level inDECIBELS of that part of a specified sig-nal contained with a band one cycle persecond wide, centered at the particular fre-quency. Ordinarily, this has a significanceonly for a signal having a continuous dis-tribution of components within the fre-quency range under ~deration. (SVH)

PRAIRIE SOILS — Psdology. A zonal greatsoil group consisting of soils formed undertemperate to cool-temperate, humid regionsunder tall graw vegetation. (SSS )

PRECIPITABLE WATER — The total at-mospheric WATER VAPOR contained ina vertical column of unit cross-sectionalarea extending between any two specifiedlevels, commonly expressed in terms of theheight to which that water substance wouldstand if completely condensed and collectedin a vessel of the same unit cross-section.(AMS) *

PRECIPITATION, n. (see HYDROME-TER) — 1. Any or all of the forms ofwater particles, whether liquid or solid,that fall from the atmosphere and reach theground. Precipitation includes DRIZZLE,RAIN, SNOW, SNOW PELLETS, SNOWGRAINS, ICE CRYSTALS, ICE PEL-LETS, and HAIL. (AMS ) * 2. The amount,usually expressed in inches of liquid waterdepth, of the water substance that hasfallen at a given point over a specifiedperiod of time. (AMS) *

PRECIPITATION EFFECTIVENESS — Ingeneral, the actual efficacy of precipitationin plant growth. The dependence of the

w



effect of precipitation on TEMPERA-TURE or EVAPORATION has been ex-pressed in many ways, such as Ktippen’sformulas for defining desert climate andThomthwaite’s precipitation effectivenessindex, (AMS) *

PRECIPITATION STATIC — Radio inter-ference (static) to aircraft communicationcaused by CORONA DISCHARGE fromradio antennas or other protuberances onaircraft flying through clouds containingice particles. (AMS) *

PRESERVATION, CYCLIC - The repre-sentation, repackaging, or repacking ofmaterial in store on which previously ap-plied protective measurea have subsequentlymatured or deteriorated to a state whererenewal of protection is necessary. ,

PRESSURE, n.— 1. A type of stress charac-terized by uniformity in all directions. Indynamic+ it is that part of the stress tensorthat is independent of VISCOSITY and de-pends only upon the molecular motion ap-propriate to the local temperature and den-sity. It is a scalar quantity expressed inunits of force per unit area. (AMS ) * 2.In meteorology, commonly used for AT-MOSPHERIC PRESSURE. (AMS)

PRESSURE, ABSOLUTE — The pressurereferred to that of a perfect vacuum. It isthe sum of the GAGE PRESSURE andATMOSPHERIC PRESSURE.

PRESSURE ALTITUDE — 1. The altitude,in the STANDARD ATMOSPHERE atwhich a given pressure will be observed. Itis the indicated altitude of a pressure alti-meter at an altimeter setting of 29.92inches of mercury (1013.2 mb) ; therefore,it is the indicated altitude above the 1013.2mb constant-pressure surface. (AMS) 2.The simulated altitude condition created inan altitude chamber by changing (usuallyby lowering) the pressure in the chamber.(NASA)

PRESSURE, DYNAMIC — The differencebetween static and Pitot pressure due torelative motion of a fluid when compressi-

bility of the fluid is not considered. Pitotpressrme is the pressure at the open end ofa PITOT TUBE. (ND)*

PRESSURE FRONT—See SHOCK FRONT.

PRESSURE, G.IGE — The pressure above .atmospheric (barometric) pressure.

PRESSURE, HYDROSTATIC (or GRAVI-TATIONAL PRESSURE)—The pressurein a fluid in hydrostatic equilibrium, i.e.,the pressure at a point due solely to theweight of fluid above. (AMS) *

PRESSURE, IMPACT — The pressure ex-erted when one object strikes another, con-sisting of pressure derived from bothSTATIC and DYNAMIC PRESSURE.(AFD) *

PRESSURE, PARTIAL — The pressure ex-erted by one constituent of a mixed gas.The sum of the partial pressures of eachconstituent of the mixture equals the totalgas pressure,

PRESSURE, RECOVERED — The pressureactually obtained when the static pressureis increased by the conversion of a portionof the kinetic energy in the stream of gasto pressure energy. The maximum recov-ered pressure would be STAGNATIONPRESSURE were it not for losses in theconversion urocess.

PRESSURE, REFLECTED — The pressurefrom an explosion, which is reflected backfrom a solid object or surface, rather thandissipated in the air. Said especially of anairburst bomb. (AFD)

PRESSURE, SATURATION—The pressureat a given temperature where vapor andliquid, or vapor and solid, can exist instable equilibrium.

PRESSURE SPECTRUM LEVEL-The ef-fective sound pressure level for the soundenergy contained within a band one cycleper second wide, centered at the specifiedfrequency. Ordinarily this has significanceonly for sound having a continuous distri-bution of ener~v within the frequency


range under consideration, The referencepressure should be explicitly stated.

PRESSURE, STAGNATION — The staticpressure that could be realized if the flowcould isentropically be brought to rest. Itdepends upon the STATIC PRESSURE,the MACH NUMBER, and the kind of gas.At low Mach numbers, it approaches thesum of the static pressure and the incom.pressible velocity head, but is increasingly~eater than this sum at higher Mach num-bers.

PRESSURE, STATIC — 1. The pressure ex-erted upon an object by air or other fluidby virtue solely of its own molecular ac-tivity resulting from its density and tem-perature, no gain tilng due to outsidework. (AFD) * 2. Acoustics. The pressurethat would exist at a mint in the absenceof sound waves. (ASA) * 4

PRESSURE TENDENCY (or BAROMET-RIC TENDENCY) —The character andamount of atmospheric pressure change fora three-hour or other specified period end-ing at the time of observation. (AMS)*

PRESSURE, TOTAL — The resultant of allcom~nents of pressure acting at a point.In relation to a PITOT TUBE, the expre%sion may be used at the equivalent of Pitotpressure. (ND)

PRESSURE, VELOCITY — 1. The pressurecapable of causing an equivalent velocity ina moving fluid if applied to move the samefluid through an orifice so that ail pressureenergy expended is converted into kineticenergy. 2. See PRESSURE, DYNAMIC.3. See WIND PRESSURE.

PREVAILING WIND DIRECTION — Thewind direction most frequently observedduring a given period. The periods mostfrequently used are the observational day,month, season, and year. (AMS) *

PROBABILITY FORECAST — A forecastof the probability of occurrence of one ormore of a mutually exclusive set of weathercontingmcies, as dktinguished from a

MIL-S7D-I 16525 MARCH1968

series of categorical statements. (AMS)

PROFILE, n.— A geometric representationof a terrain surface as an elevation-distancecurve. (WES)

PROGRAM CAM — In a process-control eya-tem wherein a controlled parameter (e.g.,dry-bulb or wet-bulb temperature) must bevaried in a periodic manner at specifiedrates between specified limits, a cam ro-tated at a constant speed and shaped suchthat the cam follower causes the controlledparameter to vary in accordance with thespecified program.

PROPAGATION, n.— The traveling of aradio wave, pressure wave, electric current,or the like through or along a medium, theact of sending such wavea or forcee throughor along a medium. (AFD)

iPSYCHROMETER, n.— An inetmment for

measuring the water vapor content of air.It is a type of HYGROMETER with twothermometers, one a wet-bulb and the othera dry-bulb. (AMS) *

PSYCHOMETRIC CHART—A nomographfor graphically obtaining RELATIVE HU-MIDITY, ABSOLUTE HUMIDITY, andDEW POINT from wet- and dry-bulb ther-mometer readings. (AMS)

PULSE, n.— A variation of a quantity whosevalue is normally constant (often zero),the variation being characterized by a riseand a decay. A common example is a veryshort burst of electromagnetic energy.(ND)

PULSE LENGTH — 1. The interval of timefrom the beginning to the end of a pulseof transmitted radiation, the puke dura-tion. (AFD) 2. The linear distance occu-pied by a pulse of electromagnetic radiationon a radar screen, the pulse width. (AFD) *3. The pulse duration multiplied by thespeed of light. (AMS) *

PUMICE, n.— A general name for highlysiliceous igneoue glasses that are so ex-tremely light and frothy that they will float

101



on water, The open spaces are minute vesi-cles formed originally by the expulsion ‘ofwater vapor or other gas from highlyheated lava. (S&V) ●

PUTTY GAGE — A type of STEP GAGEwhich provides an indication of peak accel-eration. It consists of a number of spring-Ioaded masses whose motion results. in theindentation of a putty-like material.(SVH)”

P WAVE (Also called COMPRESSIONWAVE, LONGITUDINAL WAVE, PRES-SURE WAVE) — A seismic body wave,advancing by alternating compressions andrarefactions in an elastic medium. It is thetype of wave which carries sound.

PYRHELIOMETER, n. — General term forthe class of instruments which measure the

; intensity of direct solar radiation. The in-strument consists of a radiation sensingelement enclosed in a casing which is closed.except for a small aperture, through whichthe direct solar rays enter, and a recorderunit. (AMS) *

Iates with the impact of a person walkingon it. (ADT) 2. A late vegetation] stagein the filling of a lake or pond by ericroach-ing, floating mats of plants and plant de-bris. (ADT)

QUAQUAVERSAL, adj. — Dipping from acenter toward all points of the compass, asin a dome. (S&V)

QUARTZ, n. — Crystalline silica. In its mostcommon form it is colorless and transpar-ent, but it takes a large variety of formsof varying degrees of opaqueness and col-or. It is the most common solid mineral.(ND)”

QUICKSAND, n, – Submerged, ssturatedsand into which a heavy object easily sinks.The sand is held in a very loose, unstablepacking such that a shock moves the grainsto a smaller bulk volume. The lack of bearing power may be due to seepage pressureof water percolating through the sand in anupward direction or it may be due to in-herent instability of the structure of thesand, unaided by seepage pressure. (S&V)

Q WAVE (Also called LOVE WAVE) — 1. ●Q

Q (QUALITY FACTOR) - A measure ofthe sharpness of resonance, or frequencyselectivity, of a resonant vibratory systemhaving a single degree of freedom eithermechanical or electrical. (1S0)”

QUADRANGLE, n.— A unit area that isstandardized as to form and orientation forthe purpose of systematic mapping. It isbounded on the east and, west by lines oflongitude. (meridians) and on the northand south by lines of latitude (parallels).(s&v) *

QUAGMIRE, n.— A saturated area with asurface of soft mud, or, at best, a surfaceproviding a shaky and precarious footing.(ADT)

QUAKING BOG — 1. A peat deposit so wetand unconsolidated that the surface oscil.

A transverse wave propagated along theboundary of two elaatic media, both ofwhich have rigidity; that is, both mediamust be capable of propagating transversewaves. 2. Seismology. A surface seismicwave in which the particles of an elasticmedium vibrate transverse to the directionof the wave’s travel with no vertical com-ponent. (NOO)”

R

RABAL, n.— Meteorol. 1. A method of de.termining wind speeds and directions atvarious heights, in which the height dataare obtained from RADIOSONDE observa-tions and the speed from visual tracking ofthe ballcon. (.>MS) * 2, Determination ofvarying atmosi~heric conditions by use ofa RADIOSONDE balloon. Rabals are re-ports obtained in this manner. (AD)

102


RAD, n.— Unit of absorbed dose of radia-tion. It represents the absorption of 100erga of nucledr (or ionizing) radiation pergram of the absorbing material or tissue.(JD)

RADAR, n. – Radio detection and rangingequipment that determines the distanceand usuafly the direction of objects bytransmission and return of electromagneticenergy. (JD)

RADAR, PULSED — A type of radar, de-signed to facilitate range measurement,in which the transmitted energy is emittedin periodic short pulses. The distance toany target causing a detectable echo canbe determined by measuring one half thetime interval between transmitted pulseand received echo and multiplying thisnumber by the speed of light. This is byfar the most common ty~ of radar. (AMS)

RADARSONDE, n. — A system in whichRADAR techniques are used to determinethe range, elevation, and azimuth of a ra-dar target carried aloft by a RADIO.SONDE. (AMS) ●

RADIAC, adj. — A term devised to d~ignatevarious types of radiological measuring in.struments or equipment. (This term is de.rived from the words “radioactivity detee.tion, indication, and computation”, and isnormally used as an adjextiva) (JD)

RADIAC DOSIMETER — An instrumentused to measure the ionizing radiation ab.sorbed by that instrument. (JD)

RADIANT-ENERGY THERMOMETER —An instrument which determines theBLACKBODY temperature of a substanceby measuring its THERMAL RADIA-TION. (AMS) ●

RADIANT INTENSITY — The radiantpower (flux) per unit solid angle emittedby a source of electromagnetic energy.

RADIATION, n. — See ELECTROMAG-NETIC RADIATION.

MIL-ST~l 16525 MARCH 1968

RADIATIONAL COOLING — In meteorolo-gy, the coOling of the earth’s surface andadjacent air, accomplished (mainly atnight) whenever tbe earth’s surface suffersa net loss of heat due to TERRESTRIALRADIATION. (AMS)

RADIATION DOSE — The total amount ofionizing radiation absorbed by material ortissue. (JD)

RADIATION DOSE RATE — The radiationdose (dosage) absorbed per unit of time.(JD)

R4DIATION FOG – A major type of FOG,produced over a fand area when RADIA-TIONAL COOLING reduces the air tem-perature to or below its DEW POINT.Thus, a strict radiation fog ia a nighttimeoccurrence, afthough it may begin to formby eventig twilight and’ often does notdissipate urrtif after sunrise. (AMS)*

RADIATION INTENSITY — 1. The radia-tion ddse rate at a given’ time and place. Itmay be used coupled with a figure to de-note the radiation intensity used at a givennumber of hours after a nuclear burs~ e.g.,R13 is the radiation intensity 3 hours afterthe time of burst. (JD) 2. Commonly, butinaccurately, used as a synonym for thefluz denait~ (power per unit area) of abeam of radiation or particles.

RADIATION SCATTERING — The diver-sion of radiation (thermal, electromagnet.ie, or nuclear) from ita original path aaa result of interactions or collisions withatoms, molecules, or larger particles inthe atmosphere or other media betweenthe source of radiation (e.g., a nuclear ex.plosion) and a point at some distanceaway. As a result of scattering, radiation(especially gamma rays and neutrons) willbe received at such a point from many di-rections instead of only from the directionof the source. (JD)

RADIOACTIVE FALLOUT — The eventualdescent to the earth’s surface of radioac-

103



tive matter placed in the atmosphere by anatomic ‘ or thermonuclear explosion.(AMS)*

RADIOACTIVE FALLOUT PLOT—Areasplotted on a map that outline when andwhere radioactive fallout is likely to beobserved. (AMS)

RADIOACTIVITY, n. —Spontaneous emis-sion of nuclear radiation (charged parti-cles, neutrons, and gamma rays) as a re-sult of disintegration”of a nucleus. Somenatural elements are radioactive, e.g., radi-um and uranium. Induced radioactivitycan be produced in other elements by vari-ous processes (popularly called nuclearbombardment) which create artificial iso-topes of the natural element.

RADIOLOGICAL SURVEY-The directedeffort to determine the distribution anddose rates ofradiation in an area. (JD)

RADIOMETER, n. —Any of a variety ofinstruments used to measure thermal radi.ant energy or the energy of electromagnet-ic radiation at wavelengths longer thanvisible radiation, i.e., infrared, microwave,and radio wave regions. See ACTINOME-TER.

RADIOSONDE, n. — An instrument car-ried aloft by a free, unmanned balloon andequipped with elements for determiningtemperature, pressure, and relative humid-ity and automatically transmitting themeasurements by radio. (ND)*

.RAIN, n.— PRECIPITATION of liquid wa-

ter particles, either in the form of dropsof more th,an 0.5 mm. (0.02 in. ) diameteror of smaller widely scattered drops. SeeHYDROMETER. (WMO)

RAINBOW, n.— A group of concentric arcswith colors ranging from violet to red, pr-duced on a “screen” of water drops (rain-drops, droplets of DRIZZLE or FOG) inthe atmosphere by light from the sun ormoon. This phenomenon is mainly due torefraction and reflection of light. (WMO )

RAINDROP, n.— A drop of water of diam-eter greater than 0.5 mm falling throughthe atmosphere. In careful usage, fallingdrops with diameters lying in the interval0.2 to 0.5 mm are called drizz~e drops rath-er than raindrops. (AMS) *

RAINFALL EXCESS — The volume of rain-fall available for direct runoff. It is equalto the total rainfall minus interception, de-pression storage, and absorption. (MH)

RAINFALL FREQUENCY — The numberof times, during a specified period of years,that precipitation of a certain magnitudeor greater occurs or will occur at a station.(AMS)*

RAINFOREST, n. — Generally, a forestwhich grows in a‘ region of heavy annualprecipitation. (AMS) *

RAIN, FREEZING — Rain that falls in liq-uid form but freezes upon impact to forma coating of GLAZE upon the ground andon exposed objects. When encountered byan aircraft in flight, freezing rain cancause a dangerous accretion of CLEARICING. (AMS) ●

RAIN GAGE — An instrument designed tomeasure the amount of rain that has fallen.Rain gages are classified accprding to theiroperation in the following manner: (a) re-cording rain gage, (b) nonrecording raingage, and (c) rain-intensity gage. (AMS)

RAINOUT, n.— Radioactive material in theatmosphere brought down by precipitation.(JD)

RAIN SHADOW — The region, on the leeside of a mountain or mountain range,where the precipitation is noticeably lessthan on the windward side. (AMS) *

RANDOM MOTION — The motion of mole-cules, atoms, or ions (or other extremelysmall particles) resulting from incessantrandom collisions within a fluid.

RANKINE TEMPERATURE SCALE — Atemperature scale with the degree of theFAHRENHEIT TEMPERATURE

104


SCALE and the zero point of the KELVINTEMPERATURE SCALE. The ice pointis thus 491.67 degrees Rankine and theboiling point of water is 671.67 degreesRankine. (AMS) ●

RAOB, n.— An observation of temperature,pressure, and relative humidity, obtainedby means of a RADIOSONDE. The nameraob is derived from the words radiosondeobservation. (ND )

RAPID, n.— A portion of a stream in swiftdisturbed motion, but without cascade orwaterfall. Usually used in the plural. (ND)

RAVINE, n.— A depression worn out byrunning water, larger than a GULLY andsmaller than a VALLEY; a small gorge orcanyon, the sides of which have compara-tively uniform steep slopes. (GS) ●

RAWIN, n.— Winds aloft observation madeby ballon and electronic methods withoutoptical aid. (AD )

RAWINSONDE, n.—Observation of temper-ature, pressure, humidity and winds aloft,made by electronic means. (AD)

RAYLEIGH WAVE — 1. A two dimensionalbarotropic disturbance in a fluid having oneor more discontinuities in the vorticity pr~file. 2. A wave propagated along the surfaceof a semi-infinite elastic solid, and bearingcertain analogies to a surface gravity wavein a fluid. (AMS)

REACH, n.— 1. An arm of the sea extend-ing into the land. 2, A straight section ofrestricted waterway of considerable extent:may be similar to a NARROWS, exceptmuch longer in extent. (NOO)

REAUMUR TEMPERATURE SCALE (Ab-breviated R) — A scale with the ice pointat zero degrees and the boiling point at 80degrees. with pressure of one atmosphere.(AMS)

RECIPROCITY, n.— A methud of calibra-tion wherein two measuring devices, suchas accelerometers, are compared while be-ing used in opposing positions, The devices

MII.-STD-1 16525 ~CH 1968

are then reversed in these positions and thecomparison is repeated<

RED EARTH — Highly leached, red clayeysoils of the humid tropics, usually with verydeep profiles that are low in silica and highin seaquioxides. (SSS)

REED GAGE (FRAHM’S REEDS) -An in-strument which measures the frequency atwhich an object is vibrating.

REEF, n.— A rucky or coral elevation at ornear enough to the surface of the sea to bea danger to surface vessels. A BARRIERREEF roughly parallels land but is somedistance offshore with deeper water inter-vening; a FRINGING REEF is closelyattached to a shore. (ND)

REFLECTION, n.— The return or change inthe direction of travel of particles, radiantenergy, sound waves, or other longitudinalwaves which impinge on a surface but donot enter the substance providing the re-flecting surface. (ND) *

REFLECTION, DIFFUSE — Any reflectionpruceea in which the reflected radiation issent out in many directions usually bearingno simple relationship to the angle of inci-dence. (AMS)”

REFLECTION INTERVAL, RADAR—Thetime interval between the transmission ofa radar pulse or wave and the reception ofthe reflected wave at the point of trans-mission. (AFD)

REFRACTION, n.— The process in whichthe direction of energy propagation ischanged as the result of a change in den-sity within the propagating medium, or asthe energy passes through the interfacerepresenting a density discontinuity be-tween two media. (NOO)

REFRACTION OF WATER WAVES — 1.The process by which the direction of awave moving in shallow water at an angleto the contours is changed. That part ofthe wave advancing in shallower watermoves more slowly than the other part still

105



advancing in deeper water, causing thewave crest to bend toward alignment tiththe underwater contours. 2. The bendingof wave crests by currents. (NOO)

REFRACTION, ACOUSTIC — The processby which the direction of sound propaga-tion is changed due to spatial variation inthe speed of sound in the medium. (ASA)

REG, n.— An extensive, nearly level area ina desert with a smooth floor consisting ofa layer of stones toa large to be moved bythe wind. The “desert pavement” of stonesis commonly only one stone thick and mayoverlie loose unconsolidated material.

REGULATION, n. — A twofold process inwhich a localized region on the surface ofa piece of ice melts when pressure is ap-plied to that region and then refreezeswhen the pressure is reduced. (AMS ) *

REGIMEN OF A STREAM — The systemor order characteristic of a stream; in otherwords, its habita with respect to velocityand volume, form of and changes in chan-nel, capacity to transport sediment, andamount of material supplied for transpor-tation. (MH)”

REGIONAL BOUNDARIES — Lines whichdelineate geographical areas of tbe worldfor broad planning purposes. (JD)

REGOLITH, n.— The unconsolidated mantleof weathered rock and soil material on theearth’s surface; the loose earth materialsabove solid rock. Only the upper part ofthis, modified by organisms and other soil-building forces, ia regarded by soil scien-tists as SOIL. {YA)

REGOSOLi n. — Pedology. Any one of anazonal group of soils which have under-gone little or no pedological development,lack clear-cut soil morphology, and consistmainly of unconsolidated material such asaand or silt. (ADT)

RELATIVE HUMIDITY — 1. The ratio, ex-pressed in Wrcent, of the amount of watervapor in a given volume of air to the

amount the volume of air would contain ifsaturated, (MIL-STD 21OA) 2. The ratio,expressed in percent, of the actual partialpressure of the water vapor in a given ●mixture of air and water vapor to the sat-uration pressure of pure water at the sametem~rature. (NASA)

RELAXATION TIME—In general, the timeinterval required for a system exposed tosome discontinuous change of environmentto undergo the fraction (l-e-l), or about63 percent, of the total change of statewhich it would exhibit after a period ofindefinite length. Occasionally, the fraction9/10th is used in place of (l-e-’), SO COn-texts must always be checked, to be certainof the definition employed in a given case.The relaxation time of an instrument iscommonly called ite time constant or lugcoefia”ent.

RELIEF, n.— The irregularities of the landsurface. (FM )

RENDZINA, n.— A great soil group of theintrazonal order and calcimorphic suborderconsisting of soils with brown or blackfriable surface horizons underlain by light ●gray to pale yellow calcareous material; de-veloped from soft, high!y calcareous parentmaterial under grass vegetation or mixedgrasses and forest in humid and semiaridclimates. (SSS)

RESEARCH, n.— All effort directed towardincreased knowledge of natural phenomenaand environment and toward the solutionof problems in all fields of science. This in-cludes basic and applied research. (JD)

RESIDUAL MATERIAL — Unconsolidatedand partly weathered parent material fromsoils presumed to have developed from thesame kind of rock as that on which it lies.The term resrifual is sometimes incorrectlyapplied to soils, but it can be applied cor-rectly only to the material from whichsoils are formed. (SSS)

RESIDUAL MOISTURE — Moisture held inmaterials or surfaces, such as building,

1S6


o framework, packaging materials, cordage,and painted surfaces, after the materialsare in equilibrium with the relative humidi-ty maintained in the storehouse.

RESIDUAL RADIATION — Nuclear radia-tion caused by fallout, radioactive materialdispersed artificially, or irradiation ss aresult of a nuclear explosion. (JD)

RESISTANCE THERMOMETER — A typeof electrical thermometer in which thethermal element is a substance whose elec-trical resistance varies with the tempera-ture. (AMS) *

RESONANCE, n.— 1. In general, a termapplied tO a variety of phenomena, all ofwhich involve an abnormally large responseof a system to a relatively small stirrmluswhich has the same, or very nearly thesame, frequency (or vibration period ) asthe natural frequency (or free vibrationperiod) of the system. 2. The phenomenonof amplification of a free wave or oscilla-tion of a system by a forced wave or oscilla-tion of exactly equal period. The forcedwave may arise from an impressed forceupon the system or from a boundary con-dition. The growth of the resonant ampli-tude is characteristically linear in time.(AMS) 3. Mechanics. The condition thatexista in a body m system undergoingforced vibration if any change, howeversmall, in the frequency of excitation causesa decrease in the response of the body orsystem.

Note: Velocityresonance,for example, mayoccur at a frequency different from that ofdisplacement rewmance.

RESONANT DWELL — A condition of sus-tained VIBRATION at an applied frt?quen-cy equal to a resonant frequency of a testspecimen.

RESPONSE, n.— The motion (or other out-put) resulting from an excitation (stimu-lus) under specified conditions.

Note 1: Modifying phrases must be pre.fixed to the term response to indicate whatkinds of inDut and OUtDUtare beine utilized.

107


Note 2: The response characteristic, oftinpresented graphically, gives the response asa function of some independent variablesuch as frequency or direction. For suchpurposes it is customary to assume thatother characteristics of the input (forexample,voltage) are held constant. (ASA)

RESPONSE, HARMONIC—The periodic re-sponse of a vibrating system exhibiting thecharacteristics of RESONANCE at a fre-quency that is a multiple of the excitationfrequency. (SVH)

RESPONSE, MOTION — The ratio of thedisplacement amplitude of an isolated sys-tem to the quotient obtained by dividingthe excitation force amplitude by the staticstiffness of the isolator. (SVH)

RESPONSE, SUBHARMONIC – The periodicresponse of a mechanical system exhibitingthe characteristic of resonance at a fre-quency that is a submultiple of the periodicexcitation. (ASA)

RESULTANT WIND — In climatology, thevectorial average of all wind directionsand speeds for a given level at a given placefor a certain period, as a month. (AMS) *

REVERBERATION, n.— 1. The persistenceof SOUND in an enclosed space, as a resultof multiple reflections after the soundsource has stopped. (ASA) 2. The soundthat persists in an enclosed space, as aresult of repeated reflection or scattering,after the source of the sound has stopped.(ASA)

REVERBERATION TIME — The time thatwould be required for the mean-squaresound pressure level, originally in a steadystate, to decrease 60 db after the source isstopped, (ASA)

REVERSE SLOPE — 1. Any slope whichdescends away from a given point of ref-erence. 2. In military usage a elope whichdescends away from the enemy. (AD) ●



REVERSING CURRENT -- A tidal currentwhich flows alternately in approximatelyopposite directions, with periods of slackwater at each reversal. (AMS) *

RIA, n. — A long narrow arm of the oceanpenetrating the coastline more or le~ at iright angle and narrowing gradually in-land. (S&V)

RIA SHORELINE — A shoreline character-ized by numerous RIAS; such shorelinesmay, form by the submergence of a landdissected by normal river valleys. (S&V)

RIDGE, n.— 1. A long, narrow, and usuallysharp crested land form that may be moreor less independent or a part of a largemountain or hill. (S&V) ● 2. In meteorol-ogy, an elongated area of relatively highATMOSPHERIC PRESSURE, almost al-ways associated with and most clearlyidentified as an area of maximum anticy -clonic curvature of wind flow. (AMS) ●

RIFFLE, n.— A rapid in a stream. (MH)

RIFT VALLEY - An elongate narrowtrough or valley formed by the sinking ofa strip of the earth’s crust between twomore or less parallel normal FAULTS. SeeGRABEN. (S&V)

RIME, n.— A white or milky and opaquegranular deposit of ice formed by the rapidfreezing of supercooled water drops asthey impinge upon an exposed object.(AMS) *

RIME, HARD — Opaque, granular masses ofRIME deposited chiefly on vertical sur-faces by a dense supercooled fog. Hardrime is rhore compact and amorphous thanSOFT ‘RIME, and may build out into thewind as glazed cones or feathers. (AMS ) *

RIME, SOFT — A white, opaque coating offine RIME deposited chiefly on verticalsurfaces, especially on pointa and edges ofobjects, generally in supercooled fog.(AMS) ●

RIP-RAP — Protective work on the slopingbank of a river or canal, generally consist-ing of stones, either arranged or j tistdumped.

RIPARIAN, adj. — Pertaining to the banksof a stream. (MH)

RISE TIME, PULSE — The interval of timerequired for the leading edge of a pulse torise from some specified small fraction tosome specified larger fraction of the maxi-mum value. (ASA)

RIVER BASIN — The total area drained bya river and its tributaries. (AMS)

RIVER LINE — 1. Water’s edge on the de-fender’s side of a stream. (AD) 2. Anytactical line marked by a stream. (AD)

RIVER WASH — Barren alluvial land, usu-ally coarse-textured, exposed along streamsat low water and subject to shifting duringnormal high water. (SSS)

ROCK — Civil Engimeeting. Firm and coher-ent or consolidated earth material that can-not normally be excavated by jnanual meth-ods alone.

ROENTGEN, n.— The unit of measure oftbe total quantity of x or gamma radiationabsorbed in air. This is technically definedas the amount of x or gamma radiation,which as a result of ionization, will pro-duce in one cubic centimeter of dry air atstandard conditions of temperature andpressure, ions carrying one electrostaticunit of electricity of either sign. (AD)

ROLLING GROUND or LAND — Any un-dulating land surface; a succession of lowhills giving a wave effect to the surface. Aland surface much varied by small hills andvalleys. ((X3)

ROOM. CONSTANT — A value equal to theproduct of the average absorption coeffici-ent of the room and the total internal areaof the room divided by the quantity oneminus the average absorption coefficient.(ASA) *

ROT, n. — The decomposition of organic sub-stances by microorganisms, commonly fun-gi and bacteria.

ROTTEN ICE — Floating ice or fast ice inan advanced stage of disintegration, char-acterized by honeycomb structure, weakbanding between crystals or the presence

108


I

of meltwater or sea water between grains.Also called spring sludge. (ADT)

ROUGH BROKEN LAND — Land with verysteep topography and numerous intermit-tent drainage channels but usuafly coveredwith vegetation. (SSS)

RUBBLE, n.— An unconsolidated accumula-tion of angular, rough rock fragmentscoarser than sand, broken from largermasses either by natural forces or arti-ficially by quarrying or blasting. (S&V) ●

RUBBLE LAND – Land areas with 90% ormore of the surface covered with stonesand boulders. (SSS)*

RUNOFF CYCLE — The part of the HY-DROLOGIC CYCLE undergone by waterbetween the time it reaches the land asPRECIPITATION and its subsequentEVAPOTRANSPIRATION or dischargethrough stream channels. (AMS)

RUSTING, n.— CORROSION of iron re-sulting in the formation of rrroducts on thesurface consisting largely of hydrous fer-ric oxide. (ECS)

RUST INHIBITOR — See INHIBITOR.

sSABIN, n.— A unit used in measuring or ex-

pressing the capability of a surface to ab-sorb sound, equivalent to one square footof a perfectly absorptive surface. (AFD)

SADDLE, n.— A low point on a ridge orcrestline, often at the upper ends of valleys,extending from it in opposite directions; aridge connecting two higher elevations.(GS)

SAFE BURST HEIGHT – The height ofburst at or above which the level of fall-out, or damage to ground installations isat a predetermined level acceptable to themilitary commander, (JD)

SAG AND SWELL TOPOGRAPHY — The

●undulating topography characteristic of

109


sheets of TILL. The till usually is thickenough to completely obliterate all traces offormer topography, and the postglacialdrainage is then controlled by the surfaceconfiguration of the till. (S&V)

ST. ELMO’S FIRE — A luminous dischargeof electricity from pointed objects such asthe masts and yardarms of ships, lightningrods, steeples, etc., occurring when there isa considerable atmospheric difference in po-tential. (ND)

SALINE SOIL — A nonalkali soil containingsufficient soluble salts to impair its produc-tivity. This name was formerly applied toany soil contilning sufficient soluble saltsto interfere with plant growth. (SSS)

SALINITY, n.— A measure of the quan-tity of dissolved calts in sea water. It isformally defined as the total amount ofdissolved solids in sea water in parts perthousand by weight when alI the carbonatehas heen converted to oxide, the bromideand iodide to chloride, and all organic mat-ter is completely oxidized. These qualifica-tions result from the chemical difficulty indrying the salts in sea water. In practice,ealinity is not determined directly but iscomputed from chlorinity, electrical con-ductivity, refractive index, or some otherproperty whose relationship to salinity iswell established. (NOO)

SALINOMETER, n.— An instrument fordetermining the salinity of a liquid. In itsmost common form it consists of a hydrom-eter graduated to indicate the percentage ofsalt in the solution. (ND)

SALT FOG — An atomized saline solution ofspecified concentration, recirculated withinan enclosure containing a test specimen andused to determine the corrosion resistanceof the specimen.

SALT HAZE — A haze created by the pres-ence of finely divided particles of sea saltin the air, usually derived from the evap-oration of sea spray. (ND)

SALT MARSH—F!at, poorly drained coaatal


MIL-STD-116S25 MARCH 1968

swamps which are flooded by most hightides. (NOO)

SALT PAN—1. A pool used for obtainingsalt by the natural evaporation of sea wa-ter. (ND) 2. Any undrained natural de-pression as an extinct crater, tectonic baain,or the like, in which water gathers andleaves a deposit of salt on evaporation.(s&v)

SALTATION, n. — The movement of soil andmineral particles by intermittent leaps fromthe ground when the particles are beingmoved by wind or water. (YA)

SAND, n.— 1. Soil mechanics. In the UnifiedSoil Classification System, defined as a soilthat contains more than 50 percent parti-cles greater than 0.074 mm and more than50 percent of that fraction less than 4.76mm. Types are identified as SW (well-graded sand), SP (poorly graded sand),SM (silty sand), and SC (claw sand). 2.Individual rock or mineral fragments insoils having diameters ranging from 0.5mm to 2.0 mm. Usually sand grains consistchiefly of quartz, but they may be of anymineral composition. (YA) 3. F’edotogy.The U. S. Department of Agriculture tex-tural class name pf any soil that contains85 percent or more of sand and not more”than 10 percent of clay. (YA)

SAND BAR — A ridge of sand built up to thesurface or near the surface of a river oralong a beach. (S&V)

SAND DUNE — A mound, ridge, or hill ofsand piled up by the wind on the shore orin a desert. (ND) See DUNE.

SANDS, DRY — Sandy deposits, with lowwater-holding capacity, in which there hasbeen no clear development of soil character-istics since deposition. (YA)

SAND SNOW — Snow that has fallen at verycold temperatures (of the order of —25” C).A surface cover of this snow has the con-sistency of dust or light dry sand. (AMS)

SANDSTONE, n. — A consolidated rockcomposed of sand grains cemented together.

The size range and composition of the con-stituents are the same as for sand and theparticles may be rounded or angular.(s&v)* e

SANDSTORM, n.— A strong wind carryingsand through the air, the diameter of mostof the particles ranging from 0.08 to 1 mm.In contrast to a DUSTSTORM, the sandparticles are mostly confined to the lowestten feet, and rarely rise more than fiftyfeet above the ground. (AMS) *

SANDY CLAY — Soil of the U.S. Depart-ment of Agriculture textural class contain-ing 35 percent or more of clay and 45 per-cent or more of sand. (YA) *

SANDY CLAY LOAM — Soil of the U.S. De-partment of Agriculture textural class con-taining 20 to 35 percent clay, less than 28percent silt, and 45 percent or more ofsand. (YA) *

SANDY LOAM — Soil of the U.S. Depart-ment of Agriculture textural class that con-tains either 20 percent clay or less, and thepercentage of silt plus twice the percentageof clay exceeds 30, and 52 percent or moresand; or less than 7 percent clay, less than ●50 percent silt, and between 43 percent and52 percent sand. (SSS) *

SAPLING, n.— A young tree, three feet orover in height and less than four inches indiameter,

SASTRUGI, n., PI. (SASTRUGA, Sing. ) —Wavelike ridges of hard snow formed on alevel surface, often having a steep wallwith an overhanging crest on the windwardand a long, even slope on the lee side. Theiraxes are perpendicular to the direction ofthe wind causing them.

SATURATED AIR — MOIST AIR in a stateof equilibrium with a plane surface of purewater or ice at the same temperature andpressure; i.e., air whose VAPOR PRES-SURE is the S.4TURATION VAPORPRESSURE: its RELATIVE HUMIDITYis 100 percent. (.4MS)

SATURATION, n.—l. The condition or state

110


.

*

I

of something holding something else to itsfullest capacity. (AFD) * 2. Meteorol. Thecondition in which the partial pressure ofany atmospheric constituent (usually wa-ter vapor) is equal t.o the maximum pos-sible under the existing environmentalconditions. See SUPERSATURATION.(AMS)” 3. Chemistry. Impregnation ofone substance with another until no morecan be received; combination of two Sub-stances until they neutralize each other. 4.The degree of purity of a color, se ,meaauredby the absence of an admixture of whitelight.

SATURATION DEFICIT — 1. The differ-ence between the actual VAPOR PRES-SURE and the SATURATION VAPORPRESSURE at the existing temperature.(AMS) 2. The additional amount of watervapor needed to preduce saturation at thecurrent temperature and pressure, ex-preaadd in grams per cubic meter, (AMS) ●

SATURATION OF DESICCANT—The con-dition of a desiccant which exista when ithaa absorbed sufficient moisture to be inequilibrium with saturated (100 ~. relativehumidity) air. This condition is never at-tained in proper dehumidification machineoperation.

SATURATION, PERCENTAGE OF — Tberatio of the actual weight of water presentin a given weight of dry air to the weightof water which would be present in thesame weight of dry air at saturation (100percent relative humidity) expressed aa apercentage.

SATURATION VAPOR PRESSURE — TheVAPOR PRESSURE of a system, at agiven temperature, wherein the vapor of asubstance is in equilibrium with a planesurface of that substance’s pure liquid orsolid phase; that is, the vapor pressure of asystem that has attained SATURATIONbut not SUPERSATURATION. (AMS) *

SAWTOOTH WAVE — A periodic wave theamplitude of which varies linearly withtime between a minimum and maximum


value but the time interval to increase fmmminimum to maximum is not equal to thetime interval to decrease from maximum tominimum.

SCALE, n.— The ratio between the dis-tance on a map or chart and the tom+spending distance on the earth’s surface.(AD) “

SCALE FACTOR – Value by which an actualground distance is multiplied in order tocompensate for map distortion when deter-mining the ground distance as representedon a map. (AD)

SCALING, n.— The formation at high tem-peratures ofpartially adherent layers of cor-rosion products on a metal surface. (ECS)

SCARP, n. — An escarpment, cliff, or steepslope of some extent along the margin ofa PLATEAU, MESA, TERRACE, orBENCH. (GS)

SCATTERED ICE — 1ss that covers fromone-tenth to five-tenths of the observed seasurface. (IG) ●

SCATTERING, n.— Meteorot. The processby which air molecules and particles sus-pended in the atmosphere diffuse radiationby reflecting it in different directions: thediffusive effects of changes in the refractiveindex of air layers are sometimes incIudedin the term scattering. Energy is not absorbed, but the direction, and hence thespatial distribution, of the radiation ischanged by scattering. (AMS) *

SCHIST, n.— A crystalline METAMOR-PHIC ROCK that has closely spaced folia-tion and tends to split readily into thinflakes or slabs. There is complete gradationbetween slates and schists on the one handand schiste and gneissea on the other.(s&v) *

SCINTILLATION COUNT — A count of thetotal number of light flashes produced in aphosphor by a given ionizing event.

SCORIA, n.— Rough, cinderlike, more orleas vesicular LAVA thrown out by an ex-

111



plosive eruption or ,appearing on a lavastream. The expansion and escape of en-closed gases produce the typical structure.The term is usually restricted to basaltic orclosely allied lavaa. (S&V)*

SCORIA LAND — Areas of slaglike clinkers,burned shale, arid fine-grained sandstone;characteristic of burned-out coal beds. Suchareas commonly support a sparse cover ofgrasses, but are of low agricultural value.(sss)

SCREE, n. —Same as TALUS. (GS)*

SCRUB FOREST - [n general, any area“partiafly or completely covered withcrowded bushes or stunted trees. Morespecifically, (a) the marginal forest onwind-exposed locations and on high eleva-tions, composed of short, wind-trainedtrees or low shrubs forming a transitionalzone afong the upper tirnberfine (ADT);and (b) the tropical or subtropical (Medit-erranean cfirnate) forests associated withsubhumid or semiarid climatic conditions.

SEA BREEZE — A coastal local wind thatblows from sea to land, caused by the tem-perature difference when the sea surface iscolder than the adjacent land. Therefore, itusually blows on relatively calm, sunnydays, and alternates with the oppositely di-rected, a nighttime land b~eeze. (ALMS)*

SEA FOG — A type of ADVECTION ‘FOGformed when air that haa been lying overa warm water surface is transported overa colder water surface, resulting in coolingof the lower layer of air below its dewpoint. (AMS)

SEA ICE —. Any form of ice at sea which hasoriginated from the freezing of sea water.(IG)

SEA-LEVEL PRESSURE — The ATMOS-PHERIC PRESSURE at MEAN SEALEVEL, either directly measured or, mostcommonly, empirically determined fromthe observed station pressure. (AIMS)”

SEASON CRACKING — Cracking resultingfrom combined CORROSION and internal

stress: A term usually applied to stress cor.rosion cracking of brass. (ECS)

SECONDARY FRONT — .4 FRONT whichmay form within a baroclinic cold air masswhich itself is separated from a warm airmass by a primary frontal system. Themost common type is the secondary coldfront. (AMS)

SEDIMENT, n.— Material carried in sus-pension by water; or deposits of water-borne materials. (AkfS)

SEDIMENT.4RY ROCK — Those rocks com-posed of sediment: mechanical, chemical,or organic. They are formed through theagency of water, wind, glacial ice, or or-ganisms and are deposited at the surface ofthe earth at ordinary temperatures.(s&v) *

SEDIMENT DISCHARGE — 1. The rate atwhich dry weight of sediment passes a sec-tion of a stream. (MH) * 2. The quantity ofsediment, as measured by dry weight, orby volume, that is discharged in a giventime. (MH)

SEEP; n.— A more or less poorly definedarea where water or oil oozes from theearth in small quantities. (S&V)

SEEP, v.- To appear or disappear, as wa-ter or other liquid, from a poorly definedarea of the earth’s surface. (S&V)*

SEEPAGE, n.— Water or other liquid thathas oozed or seeped through porous ma-terial. Also, the amount of such materialexpressed in terms of volume.

SEISMOGRAPH — An instrument used tomeasure and record earthquake vibrationsand other earth tremors. (AMS )

SEISMOLOGY, n.— The science of observ-ing and recording the generation and prop-agation of elastic waves in the earth re-gardless of whether these are of earth.quake or artificial origin. (S&V)

SEMIDIURNAL TIDE — The type of tidehaving two high waters and two low waterseach tidal day, with small inequalities be-

11.2


tween euceeseive high and successive lowwater heighta and durations. It is the mostcommon type of tide throughout the world.(NOO)”

SENSIBLE TEMPERATURE—The tem-perature at which “average indoor air” ofmoderate humidity would induce, in alightly clothed person, the same sensationof comfort as that induced hy the actualenvironment. (AMS)*

SENSITIVITY —Soil Mechanics. The effectof remolding on the consistency of a clay,regardless of the physical nature of thecauses of the change. The degree of sensi-tivity is different for different clays, and itmay also be different for the same clay atdifferent water contents. (S&V)

SENSOR, n.— A technical means to extendman’s natural senses, including such de-vices as VELOCITY PICKUPS, AC-CELEROMETERS, THERMOMETERS,THERMOCOUPLES, etc.; a piece of equipment which detects and indicates terrainconfiguration, the presence of military tar-gets, and other naturaI and manmade ob-jects and activities by means of energyemitted or reflected by such targeta or ob-jeets. (AD)*

SERAC, n.— A sharp ridge or pinnacle of.ice among the crevasses of a glacier. (ND)

SERIES, n.— Cartogr@~. A collection ofsheets having the same scale and carto-graphic specification collectively identifiedby the producing agency. (AD)

SETBACK, n.— Rearward jerk, caused byinertia, of free moving parta in a projectilewhen it is fired. This force is used to pushback a spring or plunger in a time fuse andeta-t the operation of the fuze. (AD)

SETTLED SNOW — Fallen snow which haslost all traces of its original crystallinestructure and has reformed into grainswhich are not usually bonded together; atype of oZdsnow. (ADT)

SFERICS, n.— The study of ATMOSPHER-ICS, especially from a meteorological point

MlL-STD-l 1652S MARCH 196S

of view. This involve9 techniques of locat-ing and tracking atmospherics sources andevaluating received signals (waveformfrequency, etc.) in terme of source. (AMS)

SHAKER, n.— See VIBRATION MA-CHINE.

SHAKER, DIRECT DRIVE — A type of VI-BRATION MACHINE consisting of a ro-tating eccentric or cam driving a positivelinkage connection which forces a displace-ment between the base and table of the ma-chine. (SVH )

SHAKER, ELECTRODYNAMIC — A typeof VIBRATION MACHINE consisting ofa table and armatum assembly with a signalcurrent driver coil which is caused to movein the annular air gap of a base assemblyforming the maghetic circuit of a directcurrent field coil. (SVH )

SHAKER, ELECTROMAGNETIC — A typeof VIBRATION MACHINE consisting ofa table and laminated iron armature aaaem-bly which is moved by magnetic attractionand repulsion from the poles of a laminatediron electromagnet core upon which a sig-nal current coil is wound, the latter asaem-bly Ming the base of the machine. (SVH)

SHAKER, HYDRAULIC — A type of VI-BRATION MACHINE which transformspower in the form of a high-pressure flowof fluid from a pump to a reciprocating mo-tion of a table, an eleetrohydraulic valveresponding to excitation signals to deliverthe high pressure fluid alternatively to OPposite sides of an actuator piston to whichthe table is mounted. (SVH)

SHAKER, PIEZOELECTRIC - A type ofVIBRATION MACHINE in which the tableis coupled on the base by means of a stackof piezoelectnc or ferroelectric ceramiccrystaIe, the table being moved by theadditive crystal strains when an excitationvoltage is applied to the electric terminalsof the crystals. (SVH)

SHAKEIt, REACTION — A type of VIBRA-TION MACHINE consisting of a softly

113



suspended table to which is attached oneor more unbalanced rotating masses andwhich is caused to vibrate due to the unbal-anced force reaction of the table, withoutforce reaction against the machine base.

SHALE, n.— A general term for lithifiedmuds, clays, and silts that are fissile andbreak along planes parallel to the originalbedding. A typical shale is so fine grainedas to appear homogeneous to the unaidedeye. (S&V)”

SHALLOW FORDING — The ability of avehicle or gun equipped with built-in wa-terproofing with its suspension in contactwith the ground, to negotiate a water ob-stacle without the use of special waterproofing kit. (JD)

SHEAR — The variation (usually the direc-tional derivative) of a vector field along agiven direction in space. The most frequentcontext for this concept is WIND SHEAR.(AMS)

SHEAR CRACK — A crack in eea ice causedby two different, simultaneous forces actingin parallel but oppoaitg directions on adj a-scent portions of the ice. The sheared partsundergo a displacement parallel to theplane of the crack. (NOO)

SHEAR STRESS — Geob~. An action orstress, resulting from applied forces, whichcauses or tenda to cause two contiguousparts of a body to slide relative to eachother in a direction parallel to their planeof contact. The term is often used synony-mously with couple, and may be employedto describe the sliding of rocks paat eachother along fractures. (S&V)”

SHEET, n.— Cartography. An individualmap or chart, either complete in itself orpart of a series. (AD)

SHEET ICE — Ice formed in a thin, smoothlayer over a water surface. (ND)*

SHELF BERG — A large mass of floating orstranded ICE broken away from an ICESHELF. The size varies from a few thou-sand square yards to 250 square miles or

more in area; in the Arctic the thicknessvaries from about 50 feet to more than 200feet. Arctic >$elf bergs are characterizedby a regularly undulating surface which

●gives them a ribbed appearance from theair; they are often referred to as ICEISLANDS. (IC)

SHELTERBELT, n.— A belt of trees orshrubs arranged as protection againststrong winds; a type of windbreak. Thetrees may be specially planted or leftstanding when the original forest is cut.(AMS)*

SHIELDING — 1. Material of suitable thick-ness and physical characteristics used toprotect personnel from radiation duringthe manufacture, handling, and transporta-tion of fissionable and radioactive materi-als. (JD) 2. Obstructions which tend toprotect personnel or materials from the ef-feet of a nuclear explosion. ( JD)

SHINGLE, n.— Small, rounded, water-worn stones. Shingle is similar to GRAVEL,but with the average size of stones gener-ally larger. (ND)

SHOAL, n.— A submerged RIDGE, BANK, ●or BAR consisting of or covered by uncon-solidated sediments (mud, aand, gravel)which is at or near enough to the watersurface to constitute a danger to naviga-tion. If composed of rock or coral, it iscalled a REEF. (NOO)”

SHOCK, n.— See MECHANICAL SHOCKand THERMAL SHOCK.

SHOCK FRONT — The twundary betweenthe pressure disturbance created by an ex-plosion (in air, water, or earth) and theambient atmosphere, water, or earth. (JD)

SHOCK ISOLATOR — A resilient supportthat tends to isolate a system from a shockmotion. (SVH)

SHOCK MACHINE — A device for subject-ing a system to controlled and reproduciblemechanical shock. (1S0 )

SHOCK MOTION — Any motion causing, orresulting from, a shock excitation. (1S0)

114


....‘“o SHOCK PULSE — A form of shock excita-tion characterized by a rise and decay ofacceleration in a relatively short perfed oftime. The major valuea of accelerations fora shock pulse are in one direction. (ISO)

SHOCK PULSE DURATION — The time re-quired for the acceleration of the pulse torise from some stated fraction of the maxi.mum amplitude and to decay to this value.(SVH)

SHOCK SPECTRUM (or SHOCK RE-SPONSE SPECTRUM) — An approxi-mate expression of the maximum respmrses(displacement, velocity or acceleration) ofan assembly of single-degree-of-freedomsystems to a sheck excitation. The r~spmrses are expressed as a function of thenatural frequencies of the systems. A shockspectmm exists for every shock excitation,whether service-induced or applied in thelaboratory. (1S0)”

SHOCK TUBE - A test device consisting ofa controlled atmosphere tube in which ashock wave is used as a driving force toproduce a high math number of very shortduration (order of milliseconds). Theshock tube is of interest in environmentsother than high-speed propulsion since theshock wave causes a tremendous increase inthe temperature of the gas.

SHOCK, VELOCITY — A mechanical shockresulting frem a sudden non-oscillarychange in velocity. (1S0) *

SHOCK WAVE — 1. The continuously prop-agated pressure pulse formed by the blastfrom an explosion in air by the air blast,underwater by the water blast, and under-ground by the earth bleat. (JD) 2. A pres-sure disturbance; which is received by theear as a noise or clap. (NASA)*

SHORE, n.— The land bordering any bedyof water. (GS)

SHORE LINE — The boundary line’ betweena body of water and the land. The shoreline shown on char-h generally approxi-mates the mean high water line. The in-

115


stantmreous line marking the junction ofwater and land, or the height of wateralong the hull of a vessel, is called waterline.

SHOWER, n.— Precipitation from a con-vective cloud. Showers are characterized bythe suddenness with which they start andstop, by the rapid cbangee of intensity, andusually by rapid changes in the ap~anceof the sky. (AIKS) *

SHRINKAGE LIMIT – Soil Mechonics. Thatmoisture content, expressed as a percent-age of the weight of the oven-dried soil,at which a reduction irr the amount ofwater will not cause a decrease in thevolume of the soil mass, but at which anincrease k, the amount of water will causean increase in the volume of the soil mass.(s&v)*

SHRUB, n.— A perwnnial plant which differsfrom a perennial herb in having persistentand woody stems; it differs from a tree inhaving low stature and a habit of branchingfrom the base.

SIEF DUNE — A LONGITUDINAL SANDDUNE of great height and length. IrI croea-section it hai a knife-edge crest, one sideof which is rounded arrd the other side ofwhich falls abruptly se a collapsing frontfacing normal to the axis of the dune. Theside on which the frent occurs depends onthe side to which the wind has temporarilyveered out of iti prevailing direction.

SIEROZEM, n. — ~edotig~. A zonal greatsoil group consisting of soils with palegrayish “A” horizons grading into calcar-sous material at a depth of one foot or leas,and formed in temperate to cool, srid cli-mates under a vegetation of desert planta,short grass, and scattered brush. (SSS)

SIGMA, n.— In random vibration terminol-Ogy, the ratio of the maximum peak accel.eration of a random acceleration time his-tory to ib3 root-mean-square acceleration.

SIGNATURE — The visible, identifyingcharacteristics of a weapon or vehiclecaused by operating in a specific envirmn-



ment. For example, the dust cloud caused byBACK BLAST of a recoilless rifle or thedust generatad by an armor column in thedesert.

SILICA GEL — A highly porous form ofsilica havitrg great surface area, whichgives it the ability to abaorh large percent-Zm of water vapor. Hence, it is a gooddesiccant, drier, or dehydrating agent,

SILT, n. — 1. Soil mechanics. The UnifiedSoil Classification System defines silt as atine-grained soil posaeaeing low plasticityin relation to the liquid limit. Types areidentified as ML (inorganic silt of lowphaticity), OL (organic silt of low plastic-ity), and MH (inorganic silt with liquidlimit greater than 50). 2. Individual min-eral particles of soil that range in diameterbetween the upper size of clay, 0.002 mm,and the lower size of very fine aand, 0.05mm. (YA) 3. Pedolog~. Soil of the U.S. De-partment of Agriculture textural class con-taining 80 percent or more of silt and leasthan 12 percent of clay. (YA) 4. Sedlmentadeposited from water in which the individ-ual grains are approximately the size ofsilt. (YA) ●

SILT LOAM — Sail of the U.S. Departmentof Agriculture textural class having (1)50 percent or more of silt and 12 to 27percent of clay or (2) 50 to 80 percent ofsilt and Iesa than 12 “~rcent of clay. (YA )

SILTY CLAY — Soil of the U.S. Departmentof Agriculture textural class having 40 per-cent or more of clay and less than 20 per-cent of sand. (YA) *

SILTY CLAY LOAM — Soil of the U.S. De-partment of Agriculture textural class hav.ing 27 to 40 percent of clay and less than20 percent of sand. (YA)

SIMPLE TONE (or PURE TONE) — 1. Asound wave, the instantaneous sound pres-sure of which ia a simple sinusoidal func-tion of the time. (ASA ) 2. A sound sensa-tion characterized by ita singleness or pitch.(ASA) 3. A sound wave of only one sinu-soidal frequency.

SIMULATED ALTITUDE — A set of airconditions maintained within a room orchamber that duplicates certain of the con-ditions, commonly pressure and tempera-ture, that usually occur at some given alti-tude. (NASA)

SIMPLE HAR.MONIC MOTION—A motionsuch that the DISPLACEMENT is a sinu-soidal function of time. (SVH )

SINGLE-DEGREE-OF-FREEDOM SYS-TEM — In shock and vibration terminol-ogy, ~ sYstem for which only one coordi-nate M required to define completely theconfiguration of the system at any instant.(SVH)

SINK (or SINKHOLE) — A depression thathas subsurface drainage only, through nat-ural hoh?s and caverns in limeetone or byseepage into a lower table (GS)

SINKAGE — The depth of soil-penetrationrequired to achieve equilibrium between ve-hicle forces and soil forces; loosely, thedepth of the rut made by a vehicle operatingoff-the-road.

SITE, n.— An area, considered as to itsecological factors with reference to ca-pacity to produce forests or other vegeta-tion; the combination of biotic, climatic,and soil conditions of an area. (SAF)

SKIMMING, n. — The diversion of waterfrom a stream or conduit by a shallowoverflow used to avoid diversion of sand,silt, or other debris carried aa bottom load.(MH)

SKIRT FOG — The cloud of steam and waterthat surrounds the engines of a missilebeing launched from a wet emplacement.(AF)

SKY TEMPERATURE — The effective tem-perature of the sky, used in determiningthe heat lost from the earth’s surface byradiation to the sky. (MIL-STD 210A)

SLEET, n. — See ICE PELLETS. (.ANIS)

SLING PSYCHROMETER — A PSY-CHROMETER in which the wet- and dry-

116


MlL-STD-l 16S

e bulb thermometers are mounted upon aframe connected to a handle at one endby means of a bearing or a length of chain.Thus, the psychrometer may be whirled byband in orxier to provide the necessary ven-tilation. (AMS)

SLIME, n.— Soft, fine, oozy mud or othersubstance of similar consistency. (NOO)

SLIP TABLE — An auxiliary assembly ucaifor horizontal vibration testing, consistingof a ta)ie coupled to a vibration exciter, anda large stationary maw, the table beingsupported on the mass by a hydrostaticfilm of lubricating oil.

SLIPPAGE RATIO — The ratio wbicb ex-pres.es the linear velocity of advanca of anautomotive vehicle aa a fraction or per-centage of the peripheral linear vebcity ofits wheels, tracks, or other tractive devices.

SLIPPERINESS — A soil condition of defi-cient traction capacity in a thin surfacelayer of a soil wbicb ie otherwise traSica-

.’0bli.

SLOPE, n. — The inclined surface of a hill,mountatn, plateau, plain, or any part ofthe surface of the earth; the angle at whichsuch surfacea deviate, from the horizontal.(GS) A S1OPSof 45 degrees is a slope of Ion 1, or 100 percent.

SLUDGE, n.— 1. Spongy whitish ice lumpsa few centimeters acroea. They consist ofshah, snow slush, and sometimes of spongyice lumps formed on the bottom of a sbal-low em and emerging at the surface. 2. Anaccumulation of ice crystals which remainseparate or only slightly frozen together.It forma a thin layer and gives the seasurface a grayish or leaden-tinted color.With light winds no ripples appear on thesurface. (NOO) 3. A mixture of oil andsolid patilcnlate generated during internalcombustion engine operation.

SLUSH, n.— Snow or ice on the ground thathas been reduced to a soft watery mixtureby rain, warm temperature, or chemical

2S MARCH 1948

SLUSHING COMPOUND — A nondryingoil, grease, or similar organic compoundwhich when coated over a metal, affordaat least temporary protection against COR-ROSION. (ECS)

SMALL HAIL — See ICE PELLETS.

SMALIACALE MAP — A map having ascale smaller than 1:600,000. (JD)

SMOG, n. — A natural FOG contaminatedby industrial or other pollutant, often oc-curring over urban aress during the preva-lence of TEMPERATURE INVERSIONS.

Note: Smog, a term coined in 1906 by DsaVOsux, originally meant a mixture of fogand smoke. Although the tsrm has expe.risncsd s rscent rim in acceptance, m ferit hea not besn sivsn prscise definition.(AMS) ●

SMOKE, n. — Foreign psrticulati matter inthe atmosphere resulting from combustionproceaaee; a type of LITHOMETEOR.When smoke is present, the disk of the sunat sunrise and sunset appears very red, andduring the daytime has a reddish tinge.(AMS)’

SMOKE AGENT — A substance wbicb,through its chemical or physical properties,produces a screening or eignsl smoke. (AD)

SMOKE, ARCTIC — Same as STEAM FOG.

SMOKE BLANKET — Dense concentrationof smoke eatabliebed over and aroundfriendly areas to protect them from airvisual observation and visual precisionbombing attack or eatabliahed over enemyareas to protect attackhg aircraft fromair defense fire. (AD)

SNAG, n. — 1. A standing dead tree fromwhich the leaves and most of the brancheahave fallen, or a standing section of thestem of a tree broken off at a height of 20feet or more. If less than 20 feet, properlytermed a Wub. (SAF) 2. A sunken log ora submerged stump. (SAF)

SNOW, n.— PRECIPITATION composed ofwhite or translucent ICE CRYSTALS,

treatment. (AMS)

●chiefly in complex branched hexagonal form

117



and often agglomerated into SNOW-FLAKES. See HYDROMETEOR. (AMS)*

SNOW ACCUMULATION (or SNOWDEPTH) —The actual depth of snow onthe ground at any instant duringa storm,or after any single snowstorm or series ofstorms. (AMS)

SNOW BLINK - See BLINK.

SNOW CONCRETE — Snow which has beencompressed at low temperatures and whichsets into p tough substance of considerablygreater strength than uncompressed sriow.(ADT) *

SNOW COVER — 1. The areal extent ofsnow-covered ground, usually expressed aspercent of total area in a given region.(AMS) 2. In general, a layer of snow onthe ground surface. (AMS) 3. The depthof snow on the ground, usually expressedin inches or centimeters. (AMS )

SNOW DENSITY — The ratio between thevolume of melt water derived from a sam-ple of snow and the initial volume of theeample. This is numerically equal to thespecific gravity of the snow. See WATEREQUIVALENT OF SNOW. (MH)

SNOWDRIFT, n. — Snow deposited behindor in front of obstacles or irregularities ofthe surface, or collected in heaps by eddiesin the wind. (AMS) *

SNOWFIELD, n. — 1. Generally, an exten-sive area of snow-covered ground or ice,relatively smooth and uniform in appear-ance and composition. This term is oftenused to describe such an area in otherwisecoarse, mountainous, or’ glacial terrain.(AMS) 2. In glaciology, a region of p+x-manent snow cover, more specificallyy ap-plied to the ACCUMULATION AREA ofglaciers. (AMS)

SNOWFLAKE, n. — An ICE CRYSTAL or,much more commonly, an aggregation ofmany crystals which falls from a cloud.Simple snowflakes (single crystals) exhibitbeautiful variety of form, but the symmet-rical shapes reproduced so often in photo-

micrograuhs are not actually found fre-quent~ ii snowfalls. (AMS)i

SNOW GAGE — An instrument for measur- ●ing the vertical depth of snow. (AMS) *

SNOW GRAINS—PRECIPITATION in theform of very small, white opaque particlesof ice; the solid equivalent of DRIZZLE.They resemble SNOW PELLETS in ex-ternal appearance, but are. more flattenedand elongated, and generally have diame-ters of leas than 1 mm.; they neither shat-ter nor bounce when they hit a hard surface.(AMS)*

SNOW, HARD PACKED — Snow which hasbeen packed by vehicular or other traffic orpossibly by the forces of nature.

SNOW LINE — In general, the outer boun-dary of a snow-covered area. It has at leasttwo specific applications: (a) the actuallower limit of the snow cap on high terrainat any given time; (b) the ever-changingequatorward limit of SNOW COVER, par-ticularly in tbe Northern Hemisphere win-ter. (AMS)

SNOW, NEW — Snow made up of crystalswhich retain all or most of their dendritic ●stmcture.

SNOW, OLD — Snow made up of roughlyunidimensional, or spherical grains. Itusually includes the various kinds of crusts.

SNOW PELLETS — Precipitation consistingof white, opaque, approximately round(sometimes conical ) ice particles having asnow-like structure, and about 2 to 5 mm indiameter, Snow pellets are crisp and easilycrushed, differing in this respect from.SNOW GRAINS. (AMS) *

SNOW, POWDER — A dry snow composedof crystals or grains which lie loosely,e.g., new powder snow, settling powdersnow, and settled powder snow.

SNOW, QUALITY OF — The ratio of heatof melting snow, in calories per gram formelting pure ice at O“C. A “quality” of 90percent means that the snow has 10 percentliquid water stored in the matrix.

118


“’m SNOW, SETTLED — Snow which has lostall traces of dendritic structure. It is xen-—erally the early stage of OLD SNOW, ‘andits grains are smaller than thoee of oldsnow.

SNOW SURVEY — The process of determin-ing depth and water content of snow atrepresentative points, for example, along asnow course. Snow surveys are usuallymade for hydrologic or water supply fore-casting. (AMS) *

SNOW, WET — Snow which is moist, un-compacted, and which will easily pack oradhere to equipment.

SNUBBER, n. — A cushion applied to oneof two non-resilient members of a shockand vibration isolator or mounting whichundergu relative motion. It is d~igned toprevent non-resilient impact.

SOAK, n.— The exposure of equipment to agiven temperature for a period of timelong enough for the temperature of theequipment to reach that of the environment

a in which the equipment is to be operated.(AFD)

—SOFT HAIL — See SNOW PELLET.

SOFTWOOD, n.— Generally, one of the tM-tanical group of treea that in most caseshave needle or scale-like leaves; the coni-fers; also, the wood produced by such trees.(SAF)

SOIL, n.—l. The unconsolidated mineral ma-terial on the immediate surface of theearth that serves as a natural medium forthe growth of land plante. (SSS) 2. Theunconsolidated mineral matter on the sur-face of the earth that has been subjectedto and influenced by genetic and environ-mental factors of: parent material, cli-mate (including moisture and temperatureeffects), macro- and microorganisms, andtopography, all acting over a peried of timeand producing a product ——soil — that dif-fers from the material from which it isderived in many physical, chemical, biologi-cal and morphological properties, and char.acteristics. (SSS)

MII.-STD-1 1652S MARCH 1968

SOIL AIR — The soil atmosphere; the gase-ous phase of the soil, being that volumenot occupied by solid or liquid. (SSS)

SOIL ASSOCIATION — Pedolegy. 1. Agroup of defined and named taxonomic soilunite occurring together in an individualand characteristic pattern over a geo-graphic region, comparable to plant seao-ciations in many ways. (SSS) 2. A map=ping unit used on general soil maps, inwhich two or more defined taxonomic unitsoccurring together in a characteristic pat-tern are combhd because the scale of themap or the purpose for which it is b&ngmade does not rwquire delineation of theindividual soils. (SSS)

SOIL BIN — A laboratory container in whichvarious soils and soil-vehicle relatkmshipsran he investigated un&r controlled con-ditions; analogous to wind tunnels or navaltowing tanks in aircraft and ship practke.

SOIL CATEGORY — Any one of tbe ranksof the system of soil classification in whichcoils are grouped on the basis of theircharacteristics (SSS)

SOIL CHARACTERISTIC — A feature of asoil that can IM seen and/or measured inthe field or in the laboratory on soil sam-ples. Examples include soil slope and stoni-ness as well se the texture, structure, color,and chemical composition of soil horizons.(YA)

SOIL CREEP — The imperceptibly slowdownward movement of slope-forming soilor rock under shear stress less than thatrequired to produce shear failure. Seasonalcreep in response to freesing and thawing,thermal expansion, or ‘changes in watercontent is confined to the upper layers ofground. (S&V)

SOIL FAILURE MODEL — A mathematicalequation describing the stress and strainstates developed in natural soils, or labora-tory soil simulating materials, when sub-jected to various external loadings that ex-ceed the failure strength.

119


MIL-STW116525 MARCH 1968

SOIL FAMILY — Psdofogy. In soil classifi-cation, one of the categories intermediatebetween the great soil group and soil series.(sss)

SOILFORMATION FACTORS — The vari-able, usually interrelated natural agenciesthat are active in and responsible for theformation of soil. The factors are usuallygrouped into five major categories as fol-lows: parent rock, climate, organisms, to-pography, and time. (SSS)

SOIL GENESIS — The mode of origin of thesoil with special reference to the processesor soil-forming factors responsible for thedevelopment of the solum, or true soil,from the unconsolidated parent material.(sss)

SOIL HORIZON — Pedohgy. A layer of soilor soil material approximately parallel tothe land surface and differing from adja.cent genetically related layers in physical,chemical, and biological properties or char-acteristics such as color, structure, texture,

consistency, kinds and numbers of organ-

isms present, degree of acidity or alka-

linity, etc. See ABC SOIL. (SSS)

SOIL “MOISTURE — Water diffused in thesoil, the upper part of the ZONE OF AER-ATION from which water is dischargedby the transpiration of plants or by soilevaporation. (MH )

SOIL MORPHOLOGY — The constitution ofthe soil including the texture, structure,consistency, color, and. other physical,chemical, and biological properties of thevarious soil horizons that make up the soilprofile. (YA)

SOIL PHASE — Pedology. Tbe subdivisionof a soil type or other claesificational soilunit having variations in characteristicsnot significant to the classification of thesoil in its natural landscape but significantto the use and management of the soil.Examples of the variations recognized byphases of soil types include differences inslope, stoniness, and thickness because ofaccelerated erosion. (YA )

SOIL REACTION — The degree of acidityor alkalinity of a soil, usually expressed asa pH value. Descriptive terms commonly *esswiated with certain ranges in pH are:extremely acid, <4.5; very strongly acid,4.5-5.0; strongly acid, 5.1-6.5; moderatelyacid, 5.6-6.0; slightly acid, 6.1-6.5; neutral,6.6-7.3; slightly alkaline, 7.4-7.8; moder-ately alkaline, 7.9-8.4; strongly alkaline,8.5-9.0; and very strongly alkaline, >9.1.See HYDROGEN ION CONCENTRA-TION and PH. (SSS)

SOIL SERIES — Pedology. The basic unitof the U. S. Department of Agriculture coilclassication being a subdivision of a familyand consisting of soils which are essentiallyalike in all major profile characteristicsexcept the texture of the “A” horizon.(sss)

SOIL, STABILIZED — Soil hardened by ad-dition of a binder such as cement. (AD)

SOIL STRUCTURE — The combination ofarrangement of primary soil particles intosecondary particles, units, or peals. Thesesecondary units may be, but usually arenot, arranged in the profile in such a man.ner as to give a distinctive characteristicpattern. (SSS)

SOIL TEXTURE — The relative proportionsof the various size groups of individual soilgrains in a mass of soil. Specifically, in theU. S. Department of A~iculture classifi-cation system it refers to the proportionsof sand, silt, and clay. (YA) *

SOIL TRACTIONABILITY — The capacityof a soil to provide trsction for nontrackedmilitary vehicles. (AFD)

SOIL TRAFFICABILITY—The capacity ofa soil to withstand traffic, especially thetraffic of militsry vehicles. (AFD)

SOIL TYPE — Pedology. The lowest unitin the natural system of the U, S. Depar-t-ment of Agriculture soil classification; asubdivision of a soil series and consistingof or describing soils that are alike in allcharacteristics including the texture of the“A” horizon. (SSS)

120


\

SOIL VALUES — A set of empirically de-termined mathematical parameters whichdescribe the measured horizontal and ver-tical stress-deformation curves of naturalsoils or laboratory soil simulating mate-rials.

SOLAR CONSTANT - The power per unitarea received from the sun outaide theearth’s atmosphere on a surface normal tothe direction of the sun at the earth’s meandistance from the sun; solar irradiance priorto ATTENUATION by the earth’s atmos-phere.

SOLARIZATION, n.— An active effect ofsunlight or ultraviolet upon glass whichresults in a reduction of transparency, andsometimes permanent coloration. A reversalor gradation sequence in a dense photo-graphic image as a result of gveat overex-posure.

SOLAR NOISE — Electromagnetic radiationfrom the atmosphere of the sun at radiofrequencies. (AF)

SOLAR RADIATION — The total electro-magnetic radiation emitted by the sun. Toa first approximation, the “sun radiates asa BLACK-BODY at a temperature of about5700”K; hence about 99.9 percent of itsenergy output falls within the wavelengthinterval from 0.20 microns to 11.0 microns,with peak intensity near 0.47 microns.(AMS) *

SOI,AR SPECTRUM — The relative poweror flux density of solar radiation per unitwavelength (or frequency) interval as afunction of wavelength (or frequency).

SOLIFLUCTION, n. – The slow downslopeflow or creep of saturated soil, ofteninitiated and augmented by frost action inhigh latitudes and at high elevations. Alsocalled soil flow. (ADT)*

SOLONCHAK, n.— Pedo20gy. A great soilgroup of the intrazonal order and halo-morphic suborder, consisting of soils withgray, thin, salty crust on the surface, andwith fine granular mulch immediately be-

MIL-STb-l 1652S MARCH 1968

low being underlain with grayish, friable,salty soil; formed under subhumid to arid,hot or cool climate, under conditions ofpoor drainage. (SSS) *

SOLONETZ — Pedofogy. A great soil groupof the intrazonal order and halomorphicsuborder, consisting of soils with a verythin, friable, surface soil underlain by adark, hard columnar layer usually highlyalkaline. (SSS) *

SOLOTH — Pedofogy. A great soil group ofthe intrazonal order and halomorphic sub-order having a gray, leached surface hori-zon, which rests upon a fine-textured,brown or dark-brown horizon, developedunder grass or shrub vegetation, mostly ina subhumid or semiarid climate. (NAS) ●

SOLUM, n. (PI. SOLA) — The upper andmost weathered part of the soil profile; the“A” and “B” horizons. (SSS)

SONE, n.— A unit of loudness. By definition,a simple tone of frequency 1000 cycles persecond, 40 decibels above a listener’s thresh-old, produces a loudness of one sone.(ASA)*

SONIC ALTIMETER — An absolute alti-meter which determines height above theterrain by measuring the time interval be-tween transmission of a sound and the re-turn of its echo. (ND)

SONIC BOOM—A noise caused by a SHOCKWAVE that emanates from an aircraft orother object traveling at or above the speedof sound. (NASA)*

SONIC THERMOMETER—A THERMOM-ETER based upon the principle that tbevelocity of a SOUND WAVE is a functionof the temperature of the medium throughwhich it passes. The velocity of a soundwave also depends upon the velocity of themedium through which it passes; therefore,this quantity must be known. (AMS ) ●

SONNE PHOTOGRAPH—Continuous stripphotography. A photograph of a strip ofterrain in which the image remaina un-broken throughout its entire length, being

121



produced by a moving film passing anaperture of extremely narrow width andsynchronized with the speed of the aircraft.(AD)

SORPTION, n.— Process of taking up andholding gas, liquid or solid particles by ab-sorption (internal solution) and/or by ad-sorption (surface adhesion ) ; specifically,the action of activated charcoal and chemi-cal agent vapors. (AD)

SOUND, n.— 1. An oscillation in pressure,stress, particle displacement, particle ve-locity, etc., in a medium with internalforces (e.g., elastic, viscous), or the super-position of such propagated oscillations.(ASA) 2. An auditory sensation evoke<by the oscillation described above. (ASA)

SOUND ABSORPTION — The change ofsound energy into some other form, usuallyheat,l in passing through a medium or onstriking a surface. (ASA)

SOUND ATTENUATION—The diminutionof sound; for instance, pressure or velocity,from one point to another due to sphericalpropagation, reflection, or dissipation.

SOUND INTENSITY (SOUND-ENERGYFLUX DENSITY or SOUND-POWERDENSITY) —The average rate of soundenergy transmitted in the specified direc-tion through a unit area normal tot hisdirection at the point considered. (ASA)”

SOUND INTENSITY LEVEL — The inten-sity level, in decibels, of a sound is 10times the logarithm to the base 10 of theratio of the intensity of this sound to thereference intensity. The reference intensityshall be stated explicitly. (ASA) *

Note: In discussing sound measurementsmade with pressure or velocity microphones,especially in enclosures involving normalmodes of vibration or in sound fields con-taining standing waves, caution should beobserved in using the terms “intensity” and“intensity level”.

SOUND LEVEL’—.4 weighted sound pres-sure level, obtained by the use of meteringcharacteristics and the weighings A, B,

or C specified in American Standard SoundLevel Meters for Measurement of Noiseand Other Sounds, 224.3-1944. (ASA)*

SO.UND POWER LEVEL — In decibels, tentimes the logarithm to the base 10 of theratio of a given power to a reference power.The reference power must be indicated.(ASA)

SOUND PRESSURE LEVEL — In decibels,twenty times the logarithm to the base 10of the ratio of the pressure of a sound tothe reference pressure. Tbe reference pres-sure must be indicated. (ASA)*

SOUND SOURCE, SIMPLE — A source thatradiates sound uniformly in all directionsunder free-field conditions. (ASA)

SOUND WAVE — A mechanical disturbanceadvancing with finite velocity through anelastic medium and consisting of longitudi-nal displacements of the ultimate particles

, of the medium, i.e., consisting of compres-sional and rarefactional displacementsparallel to the direction of advance of thedisturbance; a longitudinal wave. (AMS) *

SOUND WAVES, INTERFERENCE OF —See WAVE INTERFERENCE.

SOURCE REGION, AIR-MASS — An exten-sive area of the earth’s surface over whichbodies of air frequently remain for a suf-ficient time to acquire characteristic tem-perature and moisture properties impartedby that surface. (A MS) *

SPACE CHARGE — Any net electricalcharge that exists in a given region ofspace. In atmospheric electricity, spacecharge refers to a preponderance of eithernegative or positive ions within any givenportion of the atmosphere. (AMS ) *

SPALL, n.— A chip or fragment of rockbroken off by hammering or by naturalagencies. The thin curved pieces split offby exfoliation are examples. (S&V)

SPALLING, n. — The chipping or fragment-ing of a surface or surface coating caused,for example, by differential thermal ex-

122


.

,:*

pansion or contraction. See EXFOLIA-TION. (ECS)

SPECIES, n.— A group of plants or animalswhich have many distinctive characteris-tics in common and which produce off.spring with the same distinctive charac-teristics. (ADT)

SPECIFIC HEAT — The heat capacity of asystem per unit mass, i.e., the ratio of theheat absorbed (or released ) by unit masaof the system to the corresponding tem-perature rise (or fall). (Ahfj)*

SPECIFIC HUMIDITY — In a system ofmoist Air, the (dimensionless) ratio of themass of WATER VAPOR to the total massof the system. The specific humidity maybe approximated by the MIXING RATIOfor many purposes. (AMS) ●

SPECTRUM, n. – 1. A description of aresolution into components, each of dif-ferent frequency and (usuafly) differentamplitude and phase. (ASA) 2. A con-tinuous range of components, usually widein extent, within which waves have someSPecified common characteristic; e.g.,audio- frequency spectrum (ASA) 3. Therelative energy, power, or flux density perunit frequency (or wavelength) interval as afunction of frequency (or wavelength). 4.A graphical representation of any distribu-tion function.

SPEECH INTERFERENCE LEVEL — Theaverage, in decibels, of the sound pressurelevels of a noise in the three octave bandsof frequency 300-600 CPS, 600-1200, 1200-2400, and 2400-4800 cps.

SPEED OF SOUND — 1. The speed at whichsound travels in a given medium underspecified conditions. The speed of sound atsea level in the International Standard At-mosphere is 1108 ft/second, 658 knots,1215 km/hour. (JD) 2. In the UnitedStates’ Standard Atmosphere, 1962, andthe atmosphere adopted by the Internatio-nal Civil Aeronautics Organization, the

speed Of sound in air at zero altitude is340.294 m/see or 1116.45 ft/sec.


SPILLOVER, i.—That part of OROGRAPH-IC PRECIPITATION which is carriedalong by the wind so that it reaches theground in the nominal RAIN SHADOW onthe lee side of the barrier. (AMS)

SPIT, n.— A small point of land or narrowshoal projecting into a body of water fromthe shore. (GS)

SPORADIC PERMAFROST — One or moredeposits of perennially frozen ground sur-rounded by ground which is not perenniallyfrozen. Sporadic permafrost occurs alongthe southern limits of regions where sum-mer frost conditions are usual. (ADT)

SPOUT, n.— A phenomenon consisting ofan often violent whirlwind, revealed by thepresence of a cloud column “or invertedcloud cone (funnel cloud), protruding fromthe base of a cumulonimbus, and of a“bush” composed of water droplets raisedfrom the surface of the sea or of dust, sandor litter, raised from the ground. (WMO) *Spout includes both TORNADO and WA-TERSPOUT.

SPRAY, n. -An ensemble of water dropletstom by the wind from the surface of anextensive body of water, generally fromthe crests of waves, and carried up a shortdistance into the air. (WMO) *

SPRING, n.— A place where water issueznaturally from the rock or soil upon theland or into a body of surface water. (GS)

SPRING SNOW — A coarse, granular, wetsnow, resembling finely chopped ice, gen-erally found in the spring. Also calledcorn snow. (ADT)

SQUALL, n.— 1. A strong wind character-ized by a sudden onset, a duration of theorder of minutes, and a rather sudden de-crease in speed. (AMS) * 2. A severe localstorm considered aa a whole, that ia windsand cloud mass and (if any ) precipitation,thunder, and lightning. (AMS) *

SQUALL LINE — Any non-frontal line ornarrow band of active THUNDER-

123


MlL-STD-l 165

, .

25 MARCH 1968

STORMS (with or without SQUALLS) ;a mature instability line. ( AMS) *

STACK, n.— A lofty, isolated mass of rockleft standing in the sea by the quarryingand erosive action of the waves. (S&V)

STAGE, n.— The height of a water surfaceabove an established datum plane. (MH )

STAGE-CAPACITY CURVE — A graphshowing the relation between the surfaceelevation of the water in a reservoir, usual-ly plotted as ordinate, against the volumeb+low that elevation, plotted as abscissa.(MH)

STAGE-DISCHARGE CURVE (or RATINGCURVE) – A grsph showing the relationbetween tbe gage height, usually plotted asordinate, and the amount of water flowingin a channel, expressed as volume per unitof time, plotted as abscissa. (MH) i

STAGNATION TEMPERATURE — Thetemperature created on the leading edgesof an aircraft or spacecraft travelingthrough the atmosphere. Refers to thecomplete standstill of air molecules on theleading edges of the craft. (AF)

STAIN, n.— A discoloration of wood causedby fungus or chemical agencies. This ,in-cludes blue stain, iron-tannate stain, min-eral stain, weather stain, wound stain, etc.(SAF) “

STANDARD ARTILLERY Atmosphere— A set of values describing atmosphericconditions on which ballistic computationsare based, namely: no wind; a surface tem-perature of 15°C; a surface pressure of1000 millibars; a surface relative humidityof 787. ; and a lapse rate which yields aprescribed density-altitude relation. (AMS)

STANDARD ARTILLERY ZONE — A vertical subdivision of the STANDARD AR-TILLERY ATMOSPHERE; it may be con-sidered a layer of air of prescribed thick-ness and altitude. (AMS)

STANDARD ATMOSPHERE — See AT-MOSPHERE, STAND.4RD.

STANDARDIZE,comuare with, a

v,t. — To reduce to, orstandard; to calibrate. In

the ‘environmental field, the verificationprocess by whatever steps are necessary,to assure that all investigators in a given .field are performing in a similar mannerand will produce similar results.

STANDARD PRESSURE — In meteorology,the arbitrarily selected atmospheric pres-sure of 1000 mb to which adiabatic proc-esses are referred for definitions of PO-TENTIAL TEMPERATURE, equivalentpotential temperature, etc. Other pressuresmay be used as standard for specific pur-poses. (AMS)

STANDARD TEMPERATURE—ln physics,usually the ice point (O°C) ; less frequent-ly, the temperature of maximum waterdensity (4” C). In meteorology, this has nogenerally accepted meaning, except that itmay refer to the temperature at zero pres-sure-altitude in the STANDARD ATIv[OS-PHERE ( 15°C). (AMS)

STANDARD TEMPERATURE AND PRES-SURE — A phrase used in physics to in-dicate a temperature of O“C and a pres-sure of one STANDARD ATMOSPHERE.(AMS)

STANDING WAVE — A periodic wave(time-wise) having a fixed amplitude dis-tribution ii space. A standing wave can beconsidered to be the result of interferenceof progressive waves of the same fre-quency and kind. (1S0) ●

STANDING-WAVE RESONANT SYSTEX— 1. A resonant system terminating at anode. 2. A traveling-wave transmissionsystem terminated by a retlectmg elementin such manner that some characteristic ofthe reflected wave field will be in phasewith that of the transmitted wave field ata resonant frequency, resulting in stand-ing maxima and minima.

STAR DUNE — An eolian deposit normallycomposed of a large peak from which fouror more ridges radiate. The cross-sectional

124


,0,’ shapes may include combinations of roll-ing and crested.

~ ,0

STATE-OF-THE-GROUND CODE — Astandardized surface synoptic observationwhich describes the conditiou of the groundsurface. Basically, the states-of-thegroundare recognized as dry, moist, wet frozen,and ice or snow covered. The system hasbeen used by the World Meteorological Or-ganization since ita creation in 1950 andby ita predecessor, the International Mete-orological Organization, since 1923.

STATIC DEHUMIDIFICATION — The de-humidification of a space accomplished byplacing a predetermined quantity of desic-cant in a space to take up the moisture con.tained therein without forced air circula.tion through the desiccant.

STATIC ELECTRICITY — A negative orpositive charge of electricity that an objectaccumulates, which charge creates a sparkwhen the object comes near another objectto which it may transmit its charge, orfrom which it may receive a charge.(AFD) *

STEAM FOG — FOG formed when watervapor is added to air which is much colderthan the vapor’s source; most commonly,when very cold air drifts across relativelywarm water. (AMS ) ●

STEP GAGE — A type of instrument whichindicates that motion of a specified severityhas occurred, Generally, the severity of themotion is defined in terms of a value ofmaximum acceleration which has beenreached or exceeded. (SVH )

STEPPE, n.— A term of Russian origin fora level or rolling, treeless land, where tem-perature ranges usually are extreme.(ADT)

STEREOCOMPARAGRAPH, n. — Stereo-scopic instrument used for the preparationof topographic maps to determine groundelevations by measuring the displacement

●of their images on photographs. (AD)

125


STEREOPHOTOGRAMMETRY, n. — Pho-.togrammetry, with the aid of stereoscopicequipment and methods. (AD)

STEREOPLANIGRAPH, n.— A very accu-rate stereoscopic photogrammetric map-ping instrument with mechanical draftingattachment, capable of providing a stereo-scopic picture from overlapping photo-graphs, regardless of angle at which theywere taken. (AD)

STICKINESS — The ability of soils to clingto and build up on the running gear ofvehicles.

STIFFNESS — The ratio of change of force(or torque) to the corresponding changein translational (or rotational) deflectionof an elastic element. (SVH )

STONE, n.— A rock fragment greater thanten inchex+ in diameter if rounded, andgreater than fifteen inches along the great-er axis if flat. (SSS)

STORAGE, n. — 1. Water artificially im-pounded in surface or underground reser-voirs, for future use. The term regulationrefers to the action of this storage in modi-’fying STREAMFLOW. (MH) 2. Waternaturally detained in a drainage basin,such se GROUND WATER, channel stor-age, and depression storage. (MH) ●

STORM, n.— 1. Any disturbed state of theatmosphere, especially as affecting theearth’s surface, and strongly implyingdestructive or otherwise unpleasant weath-er. (AMS) * 2. In the BEAUFORT WINDSCALE, a wind whose speed is 56 to 63knots (64 to 72 mph). (AMS)

STORM CENTER — The area of lowest at-mospheric pressure of a CYCLONE. Thisis a more general expression than EYEOF THE STORM, which refers only to thecenter of a well-develo~d tropical cyclone,in “which there is a tendency of the skies toclear. (ND)

STORM TRACK — The path followed by acenter of low atmospheric pressure. (AMS)



STRAIN, n.— Deformation caused by stress.Technically, strain is the elongation orshortening per unit of original length of abody under tension or compression, or thedistortion in angle between two planes ina body under shear stress. (S&V)

STRAND LINE — Driftwood scattered alonga river bank or a sea coast which indi-cates the flood level or high tide mark.(ADT)

STRAIT, n.— A relatively narrow body ofwater connecting two larger bodies. (GS )

STRATIFICATION, n. – The characteristicstructural feature of sedimentwy rocksproduced by the deposition of sedimentsin beds, layers, strata, laminae, lenses,wedges, and other essentially tabularunits. (S&V)*

STRATOCUMULUS, n.— A principal cloudtype (cloud genus), predominantly strati-form, in the form of a gray or whitishlayer or patch, which nearly always hasdark parts and is non-fibrous. Its elementsare tessellated, rounded, roll-shaped, orundulatory. (AMS) *

STRATUS, n. — A principal cloud type(cloud genus) in the form of a gray layer

with a rather uniform base. Stratus doesnot usually produce precipitation, but whenit does occur it is in the form of minut?particles, such as DRIZZLE. (AMS) *

STREAM, n.— 1. A course of water flowingbetween approximately parallel banks,such as a river. (ND) 2. A long narrowarea of drift ice, usually consisting of smallfragments detached from the main belt anddrifting under the influence of wind or cur-rent. (ND) 3. A steady flow of a fluid,small solid particles, or radiant energy.

(ND)

STREAM CHANNEL — The bed where anatural stream of water runs; the trenchor depression washed in the surface of theearth by running water; a wash, arroyo,or eoulee. (GS )

STREAMFLOW, n.— The discharge thatoccurs in a natural channel. Although theterm discka~ge can be applied to the flowof a canal, the word strewnflow uniquelydescribes the discharge in a surface streamcourse. Streamflow may be applied to dis-charge whether or not it is affected by di-version or regulation. (MH) ●

STREAM GAGING — The process and artof measuring the depths, areas, velocities,and rates of flow in natural or artificialchannels. (MH)

STREAMLINE, n.— A line whose tangentat any point in a fluid is parallel to the in-stantaneous velocity of the fluid at thatpoint. (AMS)

STREAMLINE FLOW — A steady flow. offluid past a body in which the fluid remainssmooth and relati@ly unchanged, as inLAMINAR FLOW. (AFD)

STREAM ORDER — A method of number-ing streams as part of a drainage basinnetwork. The smallest unbranched mappedtributary is called first order, the streamreceiving the tributary is called secondorder, and so on. (MH)”

STRESS, n.— 1. In general, a resultant con-dition of applied force. 2. Mechanics, a. Acondition existent in a body when its in-ternal structure or surfaces resist a forcethat produces or tends to produce deforma-tion in the body. b. Molecular resistance tochange in shape or size. (AFD) *

STRESS, ALLOWABLE — The permissiblemaximum stress used in the design of astructure or component which takes intoaccount efficiency in the use of material anduncertainties in expected conditions ofservice, in properties of the material andin stress analysis.

STRESS, CLIM.4TIC — The stresses whichare components of the climatic phase of theenvironment, such as temperature, mois-ture, solar radiation, atmospheric pressure,wind, rain, etc.

●

126


STRESS CORROSION CRACKINACrack-ing resuiting from the combined effmt ofCORROSION and STRESS. (ECS)

STRESS, DYNAMIC — STRESS induced inan elastic element by the dynamic deflec.tion applied to it.

STRESS ENDURANCE LIMIT—The valueof alternating stress, repetitively appliedto an elastic element, below which the ele.ment is not expected to experience fatiguefailure after an infinite (or extremelylarge) number of stress reversals.

STRESS, ENVIRONMENTAL - The com-ponent force of an ENVIRONMENT.(Temperature, humidity, solar radiation,etc. are environmental streeses).

STRESS, INDUCED — A stress which is acomponent of the man-made phase of theenvironment, such as acceleration, shock,and vibration.

STRESS, STATIC — Stress induced in anelastic element by the static deflection ap-plied to it.

STRIKE, n. — The direction of a line formedby the intersection of a bedding plane, vein,fault, slaty cleavage, schietosity, or similargeologic structure, with a horizontal plane.It is at right anglea to the dip. (S&V)

STRUCTURE, SOIL — The arrangement ofprimary soil particles into compound par.titles or clusters that are separated fromadjoining aggregates and have propertiesunlike those of an equal mass of unaggre-gated primary soil particles. (YA) ●

SUBARCTIC, n.— 1. A region of variablewidth immediately south of the arctic.Within this area the mean temperature ofthe warmest 4-month period is lese than50 degrees Fahrenheit. (AD) 2. Those landareae which extend south from tbe north-ern limit of forest to the northern limitof the developed transportation net are con.sidered operationally to be subarctic. ALthough treeless, such coastal areas as the

MlL-STD-l 1652S MARCH ! 968

Aleutians are subarctic rather than arctic.(AD)

SUBLIMATION, n. — The transition of asubstance from the solid phaee directly tothe vapor phase, or vice versa., withoutpassing through an intermediate liquidphase. (AMS) ●

SUBLIMATION NUCLIINJS — Any particleupon which an ICE CRYSTAL may growby the process of SUBLIMATION. (AMS)*

SUBSCALE FORMATION — The precipi-tation of one or more oxides of alloying ,elements beneath the external surface ofan alloy as a result of oxygen diffusing in-to the alloy from an external source. (ECS)

SUBSIDENCE, n. — 1. Bfeteorot. A descend.ing motion of air in the atmosphere, USU.ally with the implication that the conditionextends over a rather broad area. (AMS)2. Geol. A sinking of a large area of theearth’s crust. (S&V) 3. Soil Meeham”c.c.A settling of eurface soils, particularlyunconsolidated materials, either by the in-troduction of moisture into upper layersand resulting lubrication, or by removal ofmoisture (either by pumping or loweringthe water table) from lower strata, leavingvoids filled by weight of the overburden,

SUBSOIL, n. — Pedotogg. The “B’ horizonsof soils with distinct profiles. In soils withweak profile development, the subsoil canbe defined se the soil below the plowed soil(or its equivalent of surface soil), in whichroota normally grow. (YA)

SUBSONIC, adj.-of or pertaining to speedaless than the speed of eound. (JD)

SUBSURFACE RUNOFF — That part ofprecipitation which infiltrates the surfacesoil, snd moves toward the streams asephemeral, shallow, perched ground wa-ter above the main ground-water level.(MH)*

SUBSURFACE WATER — Water that ex-ists below the surface of the LITHO-SPHERE. It may be in liquid, solid, or

127



gaseous state. See GROUND WATER andSOIL AIR. (S&V)

SUBTERRANEAN STREAM — A body offlowing water that passes through a verylarge interstice, such as a cave or cavern,or a group of large communicating inter-aticee. (S&V)

SUBTROPICAL HIGH — One of the semi-permanent anticyclonea of the subtropicalhigh-pressure belt. They appear as centersof action on mean charts of surface pres.sure. They lie over oceans, and are bestdeveloped in the summer season. (AMS)

SUCCESSION, n. — The replacement of oneplant community by another. (SAF) *

SUMMIT, n. — The highest point of any un-dulating land, as of a roljing plain; a moun-tain. The apex, the top, ~r the highest pointof any landform. (GS) ,

SUNSCALD, n.— 1. Localized injury tobark and cambium often resulting inwounds and caused by a sudden increasein exposure of a stem to intense sunshineand high temperatures. (SAF) 2. A blanch-ing of surface tissuee of leaves from sud.den exposure to hot sun. (SAF)

SUNSHINE, n.— Direct radiation from thesun, se opposed to the shading of a locationby clouds or by other obstructions. (AMS)*

SUPERCOOL, v.t. — To cool below the freez-ing point without solidification.

SUPERCOOLED CLOUD — A cloud com-posed of supercooled liquid water drops.The importance of such clouds lies in theirunstable compositions, since natural orartificial addition of ice crystals or otherice nuclei will initiate the rapid phasechange to a mixed cloud or to an ice crystalcloud. (AIMS) “

SUPERCOOLING, n.— Tbe reduction oftemperature of any liquid below the melt-ing point of the substance’s solid phase;that is, cooling beyond ite nominal FREEZ.ING POINT. (AMS) *

SUPERSATURATION, n.— In meteorolo-gy, the condition existing in a given por-tion of the atmosphere (or other space)when the RELATIVE HUMIDITY isgreater than 100 percent, that is, when itcontains more WATER VAPOR than isneeded to produce SATURATION with re-spect to a plane surface of pure water orpure ice. (AMS) ●

SUPERSONIC, adj. — Of or pertaining tospeed in excess of the speed of sound.(JD)

SUPRAPERMAFROST LAYER –Thicknessof ground above the PERMAFROST, con-sisting of ACTIVE LAYER, TALIK, andalso the PERELETOK, wherever present.(AD)

SUPRAPERMAFROST WATER–GROUNDWATER above the PERMAFROST table.(ADT)

SURFACE GEOME,TRY — The three-di-mensional configuration of the terrain sur.face. (WES)

SURFACE INVERSION — A TEMPERA-TURE INVERSION based at the earth’ssurface; that is, an increase of tempera-ture with height beginning at the groundlevel. This condition is due primarily togreater radiative loss of heat at and nearthe surface than at levels above. (ALMS)*

SURFACE RUNOFF — That part of therunoff which travels over the soil surfaceto the nearest stream channel. It is alsodefined as that part of the runoff of a drain-age basin that has not pas;ed beneath thesurface since precipitation. (MH)

SURFACE SOIL—The soil ordinarily movedin tillage, or its equivalent in uncultivatedsoil, about five to eight inches in thickness.(YA)

SURFACE STORAGE — The part of preci-pitation retained temporarily at the groundsurface as interception or depression stor-age so that it does not appear as infiltra-tion or surface runoff either during therainfall or shortly thereafter. (AMS)

128


‘o SURFACE WATER — Water on the surfaceof the earth. (MH)

SURVEY, GEODETIC — That survey whichtakes into consideration the size and shapeof the earth; implies a reference spheroidwhich represents the geoid and the hori.zcmtal and vertical control datums. (AD)

SURVEY METER — A portable instrument,such as a Geiger counter or ionizationchamber, used to detect nuclear radiationand to measure the dose rate. (AD)

SURVEY, PLANE — That survey in whichthe effect of the curvature of the earthis almost entirely neglected, and compu-tations of the relative positions of the sta-tions are made using the principles of planegeometry and trigonometry, (AD)

SWALE, n.— A slight depression in gener.ally level land, usually covered with a rankgrowth of grass and often marshy. (NAS)*

SWAMP, n.— 1. In general, any area of con-

‘0

tinuously saturated or spongy ground hav-ing poor drainage; therefore synonymouswith MARSH. 2. In botany, an area ofcontinuously saturated ground, supportinglarge aquatic plantg having submerged orfloating leafy shoots, often dominated byshrubs and trees. (ADT)

S-WAVE (Also called SECONDARY WAVE,SHEAR WAVE, TRANSVERSE WAVE)— A transverse body wave which travelsthrough the interior of an elastic medium.Originally applied to earthquake seismolo-gy where it was the second (hence: S) typeof wave to arrive at a recording station.

SWAY SPACE — The total space occupiedby all parts of a resiliently supportedbody during all of its possible translationaland rotational elastic excursions from itsstatic or quiescent position.

SWEAT, n.— Condensed water vapor on arelatively cold surface, similar tQ DEW.The term dew usually refers to condensedvapor on natural objects such as leaves

●and grass when they are cooled during the

129

MIL-ST>l 16525 MARCH 1968

night, while sweat refers more specificallyto condensed vapor on a man-made object,such as a pipe or an instrument, at anytime. (ND)

SWEEP, n.— An increase or decrease of .applied vibration test frequency betweentwo frequency limits, the rate of changeof frequency being a particular functionof time or frequency.

SWEEP RATE — In vibration teeting, (a)the rate of change of applied frequency,expressed se a function of time or frequen-CY; (b) the instantaneous value of the rateof change at a particular time or fre-quency.

SWELL, n.— 1. Ocean waves which havetraveled out of their generating area. Swellcharacteristically exhibits a more regularand longer period and has flatter creststhan waves within their FETCH. 2. A long,broad elevation that rises gently and gen-erally smoothly from the sea floor. (AIsocalled RISE. ) (NOO)”

SWELL-AND-SWALE — The type of tmpo%raphy characteristic of the ground moraineof a continentii glacier. Gentle, well-round-ed hills alternate with corresponding sub-dued depressions. (S&V)

SWELLING, n.— The expansion of woodcaused by the sorption of swelling liquids,such as water, when the liquid content ofthe material is below the fiber-saturationpoint for the liquid sorbed. (SAF) ●

SWIMMING CAPABILITY — As applied tovehicles, the ability of a vehicle to negoti-ate water obstacles by propelling itselfacross, without being in contact with thebottom. (AD)

SYMBOLIC FORM — Conventiona of ar-rangement used by international agree-ment for transmitting weather informa-tion in order to conserve time and expense.(AD)

SYNOPTIC CLIMATOLOGY — The studyand analysis of CLIMATE in terms of syn-


MlL-STD-l 165 ‘2S MARCH 1968

optic weather information principally inthe form of synoptic charta. The infor-mation thus obtained gives the cIimate ofa given locality in a given synoptic situa.tion, rather than the usual climatic param-eters which represent averages over allsynoptic conditions. (AMS ) ●

SYNOPTIC METEOROLOGY—The studyand analysis of synoptic weather informa-tion (synoptic charts, synoptic weather ob-servations). (AMS)

SYNOPTIC WEATHER CHART — A chartof any extended portion of the earth’s sur-face on which are delineated the weatherconditions at different points observed attheeame moment of actual time. (AD)

r

TABLELAND, n.— A flat or undulating ele-vated area; a plateau or mesa. (GS)

TABULAR ICEBERG — A mass of ice, witha flat tablelike surface and an upper portionformed of stratified snow or firn, which hascalved from an ice shelf. (See ICE IS-LAND and SHELF BERG). (ADT)

TACTICAL LOCALITY — An area of ter-rain which, b+cause of its location or fea-ture9, possessea a hctical significance inthe particular circumstances existing at aparticular time. (JD)

TAIGA, n, — A term of Russian origin forthe circumboreal or circumpolar forest beltof the Northern Hemisphere. The predomi-nant trees of the taiga are conifers, prin-cipally pine, fir, spruce, and larch; hard-wood apeciea also occur, as birch, aspen,and alder. (ADT)”

TALIK, n . — A Russian term applied to per-manently unfrozen ground in regions ofPERMAFROST. It usually applies to alayer which lies above the permafrost, butbelow the active layer. (AD)

TALUS, n.— A collection of fallen disinte-grated material that has formed a slope at

the fcwt of a steeper declivity, (GS)

TANGENTIAL ADFREEZING STRENGTH— The resistance to the force r~uired tosheer off an object which is frozen to theground, and to overcome the friction a!ongthe plane of contact between the groundand the object. (ADT)

TARN, n. — A small mountain lake or pool.(GS)

TARNISH, n.— Discoloration of a metalsurface due to a formation of an adherentcontinuous film of corrosion products.(ECS)

TELEMETER, n.— The measuring, trans-mitting, receiving, and indicating appara-tus for obtahing the value of a quantity ata distance. The RADIOSONDE system isa meteorological example of a telemeter, ortelemeteorograph. (AMS)

TELEMETRY—The science concerned withmeasuring a quantity or quantities, trans-mitting the results to a distant station,and interpreting, indicating, or recordtngthe quantities measured. (NASA) ●

TEMPERATE CLIMATE — Very generally,the climate of the “middle” latitudes; thevariable climate between the extremes ortropical climate and polar climate. (AMS) ●

Note: This term has no precise meaningand cannot be used ta delimit a particularrange of climatic conditions.

TEMPERATE RAINFOREST — A ty~ offorest which exists in cool but generallyfrost-freee regions of heavy annual pre-cipitation. (AMS) *

TEMPERATURE GRADIENT — The rateof change in temperature between one pointand another. ( AFD )

TEMPERATURE INVERSION—A layer ofair in which temperature increases withaltitude. The principal characteristic of aninversion layer is its marked static sta-bility. so that very little turbulent exchangecan ‘occur within- it. (AMS) *

130


TEMPERATURE, MEAN RADIANT—Thetemperature at which an objeet gives outss much radiation as it receives from i~surroundings. (AMS)*

TEMPERATURE, SURFACE—L In m+teorology, the temperature of the air nearthe surface of the earth, almost invariablydetermined by a thermometer in an IN-STRUMENT SHELTER. (AMS) AISOcalled shelter temperature. 2. h oc~nogra-phy, the temperature of the layer of seawater nearest the atmosphere. It is gener-ally determined either as bucket tempera-ture or injection temperature. (AMS)

TEMPERATURE SHOCK — I. A sudden,severe change in the temperature of a piweof equipment. 2. An environmental teat in-tended to simulate the effect of such achange.

TERMINAL MORAINE - A rampart ofdrift, predominantly TILL, deposited atthe terminus of a glacier. Also called anend moraine, frontal waitw. (ADT) ●

TERMINAL VELOCITY — Hypotheticalmaximum speed a body could attain alonga speeified flight path under given condi-tions of weight and thrust if diving through

an unlimited distance in air of specifieduniform density. (JD)

TERRACE, n. ——1. A BERM, or dieeontinu-ous segmentg of a berm, in a valley at someheight shave the flood plain, representing aformer abandoned flood plain of the streaml(MH) 2. A relatively narrow plain orbench on the side of a slope terminating ina short declivity; a plain, natural or arti-ficial, from which the surface descends onone side and ascends on the other. (GS)

TERRAIN, n.— An area considered se toits extent, and man-made and natural fea-tures in relation to its use for militaryoperations. (FM)

TERRAIN ANALYSIS — The procwa of in-te~reting a geographical area to determinethe effect of the natural and man-madefeatures on military operations. This in-

MIL-STW1 16525 MARCH 1968

eludes the influence of weather and climateon time featurea. (FM)

TERRAIN ANALYZER — A mobile instru-ment developed by the I+nd LocomotionLaboratory for rapid measurement andautomatic reduction of coil strength andterrain profile data, and consisting of amounting vehicle, a Bevameter, a gyroreferenced two point profile follower, andelectronic components.

TERRAIN ESTIMATE — That portion ofan analysis of the area of operations whichconcerns the description of the terrain,the military aspecte of the terrain, and theeffects of the characteristics of terrain onenemy and friendly courses of action, in-cluding their influence on the response tonuclear weapon effects. (FM)

TERRAIN EVALUATION — The valuationand interpretation of an area of probablemilitary operations to determine the effectof the terrain on the lines of action open taopposing forces in this area. (AD)

TERRAIN FACTOR — A specific attributeof the terrain that cm be described inquantitative terms. (WES)

TERRAIN INTELLIGENCE — Processedinformation on the military significanceof natural and man-made characteristicsof an area. (JD )

TERRAIN PROFILE — A geometric repre-sentation of the earth’s surface as an am-plitude distance curve.

TERRAIN STUDY — An analysis and inter-pretation of natural and man-made fea-tures of an area, their effects on militaryoperations, and the effect of weather andclimate on these features. (JD)

TERRAIN TRAFFICABILITY — The abil-ity of terrain to support the passage ofvehicles. (WES )

TERRAIN TYPE — A region throughoutwhich a specified assemblage of factora oc-curs. (WES)

131



TERRESTRIAL RADIATION (or EARTHRADIATION) — The total INFRAREDRADIATION emitted from the earth’s sur-face; to be carefully distinguished fromeflective terrestrial radiation, atmosphericradiation, and INSOLATION. (AMS)

TEST, ACCELERATED — A test designedto shorten testing time by increasing theseverity of the tqst. This includes whatmight be termed “aggravated” testingwhere the limits are extended so as to in-troduce a greater degree of severity.

TEST, DESTRUCTIVE, n. — 1. A test inwhich materiel or equipment is subjectedto environmental conditions which are in-herently damage-producing or destructive.2. A test in which materiel or equipmentis intentionally damaged to determine itsdamage or fatigue resistance.

TEST, ENDURANCE - A dynamic fatiguetest (e.g., vibration test) usually conductedat accelerated stress levels.

TEST, ENVIRONMENTAL FIELD—A testin which a piece of equipment or an entiresystem ia expoaed or operated under naturalenvironmental conditions.

TEST, ENVIRONMENTAL SIMULATION— A test in which a piece of equipment oran entire system is exposed or operatedunder simulated service conditions, usuallyin a laboratory.

TEST, NONDESTRUCTIVE — 1. A test inwhich materiel or equipment is subjectedto environmental conditions which are in-herently non-damaging or non-destructive.2. A test in which materiel or equipment issubjected to inherently damage-producingconditions, but the stress levels or exposuretimes are intentionally reduced to preventequipment damage or destruction.

TEST, SIMULATED SERVICE — A con-trolled test, usually conducted in a labora-tory, designed to produce results havinga meaningful relationship to those pro-duced in service under natural environ-mental conditions.

TEXTURAL CLASS — Pedology. Kinds ofsoil material according to the proportionsof sand, silt, and clay. The principal U. S.Department of Agriculture textural classesin soil, in increasing order of the amountof silt and clay, are as follows: sand, loamysand, sandy loam, loam, silt loam, silt,sandy clay loam, clay loam, silty clay loam,sandy clay, silty clay, and clay. (YA) *

THALWEG, n. — GeoL 1. The line followingthe lowest part of a valley, whether underwater or not. 2. The line of continuous msx-imum descent from any point on a landsurface, or that cutting all contours atright angles. (S&V) *

THAW, n.— A weather condition occurringwhen the temperature rises abave the freez-ing point and ice and snow melt. (ADT)

THAWING INDEX — The number of de-gree days (above and below 32°F) be-tween the lowest and highest points onthe cumulative degree days time curve forone thawing season. It is used as a measureof the combined duration and magnitudeof above-freezing temperatures occurringduring any given thawing season. (ADT)

THEORETICAL GRAVITY — The value ofgravity at the earth’s surface if the earthwere a perfect sphere with no variation inmass to induce anomalies. (AF)

THERMAL, n.— A relatively small-scale,rising current of air produced when theatmosphere is heated enough locally bythe earth’s surface to produce absolute in-stability in its lowest layers. For example,glider pilots seek out and ride “thermals,”showing how strong and persistent thethermal updraft may be.

THERMAL BARRIER—.1. A popular termfor flight speed limitations imposed byaerodynamic heating. Also called the heat-banier. (NASA) 2. An insulation wall,layer, blanket, enclosure, or heat exchangerdesigned to protect equipment from theeffects of high temperatures.

THERMAL CONDUCTIVITY — An intrin-

132


sic physical property of a substance, de-

‘*scribing its ability to conduct heat as aconsequence of molecular motion. (AMS ) *

THERMAL DETERIORATION — Impair-ment of physical properties due to effectsof high or very low temperatures.

THERMAL EFFICIENCY—In climatolo-gy, an expression of the effectiveness oftemperature in determining the rate ofplant growth, assuming sutlicient mois-ture. (AMS)*

THERMAL EXPOSURE — The total nor-mal component of thermal radiation strik-ing a given surface throughout the courseof a detonation; expressed in the units:calories per square centimeter. (AD)

THERMAL HEATING – Aerodynamic heat-ing produced by supersonic snd hyperson-ic travel through the atmosphere; transferof heat from a laminar or turbulent flowaround the nose of a re-entry body as itloses kinetic energy. (AF)

THERMAL INSTABILITY — 1. The insta-

● bility resulting in free CONVECTION ina fluid heated at a boundary. (AMS) * “2.In meteorology, the instability of a bodyof air with respect to its temperature dis-tribution. (AFD) *

THERMAL LOAD — Stresses imposed upona missile structure because of expansionor contraction (or both) of certain struc-tural elements by aerodynamic heatingduring flight and re-entry, by exposure tothe heat of a rocket flame, or by coolingeffects of liquid o~ygen in the oxidizersystem. (AF )

THERMAL RADIATION — 1. The heat andlight produced by a nuclear explosion. (JD)2. Electromagnetic radiation emitted byany substance as a result of thermal ex-citation of its molecules.

THERMAL SHOCK — See TEMPERA-TURE SHOCK.

THERMISTOR, n.— A device whoss elec-trical resistance varies markedly and mon-

MIL-STD-1 16525 MARCH 1968

otonically and which possesses a negativetemperature coefficient of resistivity. Thethermistors used in meteorology are com-posed of solid semi-conducting materialswhose resistance decreases 4 percent per(7?. They are constructed in a variety ofsizes, and may be obtained with thermaltime-constants of a mini-second or less.Meteorological applications include THER-MOMETERS, ANEMOMETERS, a n dBOLOMETERS. (AMS)

THERMOCOUPLE, n. — A temperature-sensing element which converts thermalenergy directly into electrical energy. Inits basic form it consists of two dissimilarmetallic electrical conductors connected ina closed loop. One pair of junctions form athermocouple, several pairs form a thermo-pile. If electrical energy is passed througha thermocouple it creates “cold” (Peltiereffect) which can be used for refrigeration.

THERMOGRAM, n. — The record” of aTHERMOGRAPH. (AMS)

THERMOGRAPH, n. — + self-recordingTHERMOMETER. The thermometric ele-ment is most commonly either a bimetalstrip or a BOURDON TUBE tilled with aliquid. (AMS) *

THERMOKARST, n, — Karst-like topo~graphic features produced by the meltingof ground ice and the subsequent settlingor caving of ground, characterized by anuneven topography with short ravines, sinkholes, funnels, and caverns similar to thoseproduced in a limestone tei-rain by thesolvent action of water. (AD)

THERMOMETER, n.— An instrument formeasuring temperature by utilizing thevariation of the physical properties of sub-stances according to their thermal states.(AMS) *

THERMOMETER. SONIC — A thermome-ter based on the”principle that the velocityof a sound wave is a function of the tem-perature of the medium through which itpasses.

133


MlL-STD-l 16S25 MARCH 1968

THIN NATURAL SCREEN — Naturalgrowth left in front of entrenchments andemplacements to aid in concealing them.(AD)

THUNDER, n.- The sound emitted by rap-idly expanding gases along the channel ofa lightning discharge. (AMS) *

THUNDERHEAD, n. — A popular term forthe incus (“anvil” ) of a cumulonimbuscloud; or, less appropriately, the upperportion of a swelling cumulus, or the entirecumulonimbus. (AMS)

THUNDERSTORM, n.— In general, a localstorm invariably produced by a cumulo-nimbus cloud, and always accompanied byLIGHTNING and THUNDER, usuallywith strong gusts of wind, heavy rain, andsometimes HAIL. It is usually of ebort dur-ation, eeldom laeting over two hours forany one storm. (AMS) *

TIDAL CURRENT — The alternating hori-zontal movement of water associated withthe rise and fall of the tide caused by theastronomical tide-producing forces. In rel-atively open locations, the direction oftidal currents rotates continuously through360 degrees diurnally or semidiurnally. Incoastal regions, the nature of tidal currentswill be determined by local topography aswell. (NOO)

TIDAL FLAT—A marsh or sandy or muddycoastal tlatland which is covered and uncov-ered by the rise and fall of the tide. (NOO )

TIDAL MARSH — Any marsh or flatland,the surface of which is wetted by a tidalflow. (GS)

TIDE, n.— The periodic rising and fallingof the earth’s ocwms and atmosphere. Itresults from the tide-producing forces ofthe moon and sun acting upon the rotatingearth. This disturbance actually propa-gates as a wave through the atmosphereand through the surface layer of theoceans. (NOO) *

TIDE GAGE — A device for measuring theheight of TIDE. It may be simply a grad-

uated staff in a sheltered location wherevisual observations can be made at anydesired time; or it may consist of an elab.orate recording instrument (sometimescalled ?mzrigr’aph) making a continuousgraphic record of tide height against time.Such an instrument is usually actuated bya float in a pipe communicating with thesea through a small hole which filters outthe shorter waves. (NOO)

TILL, n.— Unsorted and unstratified rockfragmente ranging in size from clay tobouldere, deposited directly by a glacier.Sometimes called bordder CLW or glnctidW. (ADT)

TILL PLAIN — Relatively level area ofGROUND MORAINE consisting of till.

TIMBERLINE, n.— 1. The upper limit oferect trees in mountainous regions. (ADT)2. The northern limit of erect trees in theArctic. (ADT ) Also called tree km or for-est limit (both senses).

TOMBOLO, n.— A sandbar built by the sea,tying an island to the mainland. (GS)

TONE, n.— 1. A sound wave capable of ex-citing an auditory sensation having pitch.(ASA) 2. A sound sensation having pitch,(ASA)

TOPOGRAPHIC MAP — A map which pre-sents the vertical position of features inmeasurable form as well as their horizontalpositions. (JD)

TOPOGRAPHIC PLOT — Representation,by means of contour lines, of the groundrelief of an area shown in a stereoscopicmodel. (AD)

TOPOGRAPHY, n.— The physical” features,both natural and man-made, of the earth’ssurface. In terrain analysis the followingcategories of topographical featurea areconsidered: relief, drainage, surface ma-terials, vegetation, special physical phe-nomena, and man-made (cultural ) features.(FM)

TORNADO, n .—A violently rotating column

134


*of air, pendant from a cumulonimbus cloud,and nearly always observable as a “funnelcloud” or tuba. On a local scale, it is themost destructive of all atmospheric phe-nomena, (AMS) *

TORR, n.— A unit for measurement of astate of vacuum, defined as l/760th of astandard atmosphere; a torr is very nearlyequal to a millimeter of mercury.

TORSIOGRAPH, n.— A type of VIBRO-GRAPH designed for the measurement oftorsional vibration.

TOUGHNESS, n.— The ability of materialto absorb energy during plastic deforma-tion.

TOWN FOG – An ICE FOG created byextremely low temperatures (minus 50 to65 degrees Fahrenheit), usually noticeableover more or less densely inhabited places,because of the conflict between locallygenerated warm moist air and the surround-ing cold air. At extremely low temperatures

e

such a fog may appear over a body oftroops, herd of cattle, gasoline poweredvehicles, artillery fire, etc. (AD) *

TOWNSEND SUPPORT — A fixed supportmounting MAXIMUM and MINIMUMTHERMOMETERS of the liquid-in-glasstype. The support holds the thermometersat the correct operating attitude and alsopermits their rotation for resetting whendesired. (AMS)

TRAFFICABILITY — Capability of terrainto bear traffic. It refers to the extent towhich the terrain will permit continuedmovement of any and/or all types of traf.tic. (AD)

TRANSDUCER, n.— A device for convert-ing energy from one form to another. Forexample, a THERMOCOUPLE transducesheat energy into electrical energy. (AMS)

TRANSMISSIBILITY — The non-dimen.sional ratio of the response amplitude of asystem in a steady-state forced vibrationto the vibration amplitude. The ratio may

a

be one of forces, displacements, velocities,


or accelerations. (SVH)

TRANSMISSIBILITY, ABSOLUTE ~, (a)For foundation motion excitation, the ratioof the vibration amplitude of a piece ofequipment to the vibration amplitude ofthe foundation; (b) for force excitationfrom within a piece of equipment, the ratioof the force amplitude transmitted to thefoundation to the amplitude of the existingforce. (SVH)

TRANSMISSIBILITY, RELATIVE — Theratio of the relative deflection amplitudeof an ISOLATOR to tbe displacement am-plitude imposed at the foundation. (SVH)

TRANSVERSE DUNE — A ridge of sandoriented at a right angle to the directionof the prevailing wind. Cross sectionalshape is generally asymmetric and crested,with some areas rolling.

TRIAXIAL TEST — Soil Mechanics. A testto determine the maximum shearingstrength of a soil. Also called confined corn.pression test.

TROPICAL CYCLONE — The general termfor a CYCLONE that originates over thetropical oceans. By international agree-ment, tropical cyclones have been classitledaccording to their intensity, as TROPICALDEPRESSIONS, TROPICAL STORMS,and HURRICANES or TYPHOONS.(AMS) *

TROPICAL DEPRESSION—A TROPICALCYCLONE in which the eurface windspeed is Iese than 34 lmote (38 miles perhour).

TROPICAL RAINFOREST — A type of for.est which exista in tropical regions whereprecipitation ia heavy (generally morethan 100 inches per year). It consistsmainly of a wide variety of lofty broad-leaf evergreen trees which carry a profu-sion of parasitic or climbing plants.(AMS)”

TROPICAL STORM — A TROPICAL CY.CLONE in which the surface wind speed

.—13s


MlL-STD-l 165”2S MARCH 1960

is at least 34, but riot more than 63 knots.(JD)

TROPICALIZATION — Preparation of ma-teriel to limit infiltration of moisture intocritical parts of equipment and to kill anddiscourage fungiferous growths, therebypermitting storage and use in tropical re-gions. (AD)

TROPOPAUSE, n. — The boundary of theTROPOSPHERE, usually characterized byan abrupt change of LAPSE RATE. Thechange is in the direction of increased at-mospheric stability from regions below toregions ahove ~he tropopause. (AMS) *

TROPOSPHERE, n.— That portion of theatmosphere from the earth’s surface to theTROPOPAUSE: that is, the lowest 10 to20 km of the atmosphere. The troposphereis characterized by decreasing temperaturewith height, appreciable vertical wind ,mo-tion, appreciable water vapor content, andWEATHER. (AMS) *

TROUGH, n.— In meteorology, an elongatedarea of relatively low atmospheric pres-sure; the opposite of a RIDGE. (A MS) *

TRUE NORTH — The direction from an ob-server’s position to the geographic northpole. (AD) ●

TSUNAMI, n.— (Also called seismic seawave and, popularly, tidal wave) — Anocean wave produced by a submarineearthquake, landslide, or volcanic erup.tion. These waves may reach enormous di-mensions and have sufficient energy totravel across entire oceans. Tsunamissteepen and increase ip height on ap-proaching shallow water, inundating low-lying areas, and where local submarinetopography causes extreme steepening,they may break and cause great damage.Tsunamis have no connection with tides;the popular name is entirely misleading,(AMS)*

TUBERCULATION, n.— The formation oflocalized corrosion products scattered overthe surface in the form of knoblike

mounds. (ECS)TUNDRA, n.— 1. A flat or gently rolling

area, having a MUCK to rock ,surface overPERMAFROST, above or north of theTIMBERLINE. (ADT) * 2. In botany, amixture of several types of vegetation oc-curring in arctic and alpine districts, be-yond and above timberline, where the plantcover includes low shrubs, herbs, sedges,grasses, lichens, and mosses. (ADT)

TUNDRA SOIL — PedologV. One of a seriesof a zonal group of soils having a toughfibrous peaty mat underlain by a dark-colored humus-rich stratum, which gradesinto lighter colored gray or mottled soilbeneath. (ADT) *

TURBIDITY, n.— In meteorology, any con-dition of the atmosphere which reduces itstransparency to RADIATION, especiallyto visible radiation. (AMS) *

TURBULENCE, n. — A state of fluid flowin which the instantaneous velocities ex-hibit irregular and apparently randomfluctuations so that in practice only statis-tical properties can be recognized and sub.jetted to analysis. (AMS) *

TURBULENT FLOW — A fluid flow char.acterized by TURBULENCE. (AIMS)

TUSSOCK, n. — A tuft of grasses or grass-like plants. (.ADT)

TWILIGHT, n.— The periods of incompletedarkness following sunset (evening twi-light) or preceding sunrise (morning twi-light), Twilight is designated as civil, WZU.tical, or astronomical, as the darker limitoccurs when tbe center of the sun is 6“,IZO, or IS9 below the celestial horizon, re-spectively, (ND)

TYPHOOX, n. — .4 severe TROPICAL CY-CLONE in the western Pacific. (See HUR-RICANE) (AMS)$

u

ULTRASONIC, adj. — Of or pertaining to

136


frequencies above those that affect the hu-man ear, i.e., above 20,000 cycles per sec-ond. (AFD)”

ULTRASONIC RELIEF MAP — A specialmap made of various sound reflecting ma-terials, used with the ultrasonic trainer soas to simulate the radar reflection thatwould occur from that part of the earthrepresented. (AFD)

ULTRAVIOLET RADIATION — Electro-magnetic radiation of shorter wavelengththan visible radiation but longer than x-rays; roughly, radiation in the wavelengthinterval from 10 to 4000 angstroms.(AMS) ●

UMBRA, n.— The darkest part of a shadowin which light is completely cut off by anintervening object. A lighter part sur-rounding the umbra, in which the light isonly partly cut off, is called the pwzwnbra.(ND)

UNDERCURRENT, n.— A water currentflowing beneath a surface current at a dif-ferent speed or in a d~fferent direction.(NOO)

UNDERFLOW, n.— The downstream flowof water through the permeable depositsthat underlie a stream and that are more’or less limited by rocks of low permea-bility. (MH)

UNDERGROWTH, n.— Small treea andshrubby plants growing under a forestcanopy. (SAF)

UNDERSTORY, n.— In botany, the youngor stunted treee in a forest which are belowthe level of the main canopy. (ADT)

UNDERTOW, n.— 1. A seaward flow nearthe bottom of a sloping beach. 2. The sub-surface return by gravity flow of the watercarried up on shore by wavee or breakers.(NOO)

UNDISTURBED, adj. — 1. Geol. Applied togeologic structures in which the strata lieessentially horizontal or, as in a coastalplain, with gentle seaward dip. 2. Soil Me-

MIL-STW1 16S2s MA2CH 1943

cAunics. Undisturbed samples may be de-fined broadly se samplaq in which the ma-terial hae been subjected to so little dis-turbance that it is suitable for all labora-tory teste and thereby for approximatedetermination of the strength, consolida-tion, and permeability characteristics andother physical properties of the materialin situ. (s&v)

UNFREEZING, n.— The upward movementof etones to the surface as a result of re-pea@d freezing and thawing of the con-taining soil. (ADT)

UNIT HYDROGRAPHY — The hydrographyof direct runoff from a storm uniformlydistributed over the drainage baein duringa specified unit of time; the hydrographyie reduced in vertical scale to correspondto a volume of runoff of one inch from thedrainage basin. (MH) ●

UNSTABLE WAVSA wave motion whoseamplitude increases with time or whosetotal energy increaees at the expanse ofits environment. (AMS)

UPLAND, n. — A highland; ground eleva~dabove the lowlands along rivers or betweenhills. (GS)

UPPER AIR — In synoptic meteorology andin weather observing, that portion of theatmosphere which is above the lowerTROPOSPHERE., No distinct lower limitis set but the term is generally applied tothe levels above 850 mb. (AMS)

UPPER FRONT—A FRONT which is prese-nt in the UPPER AIR but does not ex-tend to the ground. (AMS)

UPSLOPE FOG — A type of FOG formedwhen air flows upward over rising terrainand is, consequently, adiabatically cooledto or below ite DEWPOINT. (AMS)

UPWELLING. n.— The Droceas by whichwater rises from a lower to a higher depth,usually as a result of divergence and off-shore currents. It is meet prominent wherepersistent wind blows parallel to a coast-line so that the resultant wind-driven cur’-

137



rent sets away from the coast. (N’00)”

T_T.SHAPED VALLEY — A valley having adistinctive rounded profile and a gentlegradient bottom resulting from the abra-sive and plucking action of the glacier itonce contained. (ADT)

v

VACUUM, n. — I. An enclosed space fromwhich air is evacuated to reduce the atmos-pheric pressure inside the enclosure to avery low value. 2. A region of space con-taining a negligible amourit of matter.

VALLEY, n.— A depression in the land sur-face, generally elongated and usually con-taining a stream; low land bounded byhills or mountains; a sink. (GS)

VALLEY GLACIER—A GLACIER whichflows down a valley. (IG)

VALLEY TRAIN — An outvmsh deposit ex-tending downstream from a glacier’s ter-minus or terminal moraine, usually con-fined by valley sides. The valley train mayor. may not merge with the outwash plain.(ADT) ●

VAPOR, n, — Any substurrce existing in thegaseous state at a temperature lower thanthat of its critical point; that is, a gas coolenough to be liquefied if sufficient pressurewere applied to it. (AMS ) *

VAPOR DENSITY — Same us ABSOLUTEHUMIDITY.

VAPORIZATION, n. — Same as EVAPOR.ATION.

VAPOR PRESSURE — 1. The pressure ex-erzed by the vapor of liquid in a confinedspace such that vapor can form above it.(ND) 2. The pressure of water vapor inthe air; that part of the total ATMOS-PHERIC PRESSURE which is due towater vapor. (ND )

VARVE, n. - A pair of sediment layersideally representing a year’s record of melt

water deposition in a glacier-fed lake orbay. The laminated soil structure of varvesis similar in appearance to annual growth ‘erings in trees. The srdiments are kno\vn asrcri-ved clays or ucrt, cd sediments. (.\DT) “

VEHICLE CONE INDEX (AbbreviatedVCI) — The index assigned to a givenvehicle that indicates the minimum soilstrength required for .40 to 50 passes ofthe vehicle. (TB ENG 37)

VEHICLE GROUXD MOBILITY — Themeasure of th,. ability of an automotivevehicl. to traverse the variety of terrainconditions. inc!u ding inland waterwwys,found on the surface of ths earth, and in aminimum time with minimum support andremaining capable of performing its de.sign function.

VELOCITY, n. — Rate of mutiori iII a givendirection. (ND)

VENTIFACT, n. — A stone fashioned wmodified by wind-driven debris. (ADT) “

VENTURI TUBE — A tube designed tomeasure the rate of flow of fluids. It con.sists of a tube having a construction orthroat at its midsection. The difference be-tween the pressure measured at the inletan’d at the throat is a function of the fluidvelocity. ( AIMS) *

VERTICAL OBSTACLE — .\n obstacle thatforces a vehicle to move in the verticalplane while surmounting it. (WES)

VIBRATION, n. — 1, A periodic or randommotion of the particles in an elastic bodyin alternately opposite directions. (AFD)2. The variation with time of the magni-tude of a quantity, which is descriptive ofthe motion or position of a mechanical sys-tem, when the magnitude is alternatel:-greater and smal!er thaIl suln~ averagevalue, (1S0)

VIBRATION, COJIPLEX \F’At’E —Vibca-tion consisting of sinusoidal componentswhich ire not harrnonica]ly rdated to oneanother. (SVH) ‘

138


*

●

VIBRATION, FORCED (or ‘FORCED OS-CILLATION ) — The oscillation of a sys-Lem is forced if the response is imposed byan excitation. If the excitation is periodicand continuing, the oscillation is steady-stab?. (ASA )

VIBRATION ISOLATOR — A resilient sup-port that tends to isolate a system fromsteady-state excitation. (SVH)

VIBRATICIN MACHINE—A device for sub-jectin~ a mechanical system to controlledand reproducible mechanical vibration.(SVH)

VIBRATION, SELF-INDUCED (or SELF-EXCITED ) — The vibration of a mechan.ical system is self-induced if it results fromconversion, within the system, of non.os-cillatory excitation to oscillatory excita-tion. (ASA)

VIBRATION, STEADY-STATE — See VI-BRATION, FORCED.

VIBRATION, SWEPT RANDOM — A typeof random vibration test in which the testspecimen is subjected to a narrow bandor random excitation, swept across thetotal frequency spectrum. The bandwidthof the filter may be constant or a constantpercentage of the center frequency.

VIBRATION, TRANSIENT — Temporarilysustained vibration of a mechanical sys-tem. It may consist of forced or free vibra.tion, or both. (SVH)

VIBRATORY REED METER — A device tomeasure the frequency of an excitation bydetecting the RESONANCE of one or morevibratory reeds.

VIBROGRAPH — A mass-spring type ofDISPLACEMENT PICKUP with seif-con-tained means for recording the relativemotion between the mass and the case, con-sisting of a recording medium containedon a supply spool, a transport mechanismfor the recording medium, and a take-upspool. (SVH )

VIRGA, n.— Wisps or streaks of water or

M1l-STb-l 16515 MARCH 1968

ice particles falling out of a cloud but evap-orating before reaching the earth’s sur-face as PRECIPITATION. (AMS) ●

VIRTUAL PRESSURE — The pressure ofa parcel of MOIST AIR when it has thesame density as a parcel of dry air at thesame temperature. (AMS)

VIRTUAL TEMPERATURE — The ficti-titious temperature which dry air musthave at a given pressure in order to havethe same density as moist air at the samepressure.

VISCOMETER, n. — An instrument formeasuring flow properties. The term vis-cometer is preferred to viscosinwter.

VISCOSITY, n.— 1. That molecular proper-ty of a fluid which enables it to eupporttangential stressee for a finite time andthus to resist deformation. (AMS) 2. Theproperty of a fluid that resists internalflow by releasing counteracting forces.

VISCOSITY, ABSOLUTE — For a givenliquid, the force which will move 1 squarecentimeter of plane surface with a speedof 1 centimeter per second relative toanother parallel plane surface from whichit is separated by a layer of tbe liquid 1centimeter thick. This viscosity ia ex-pressed in DYNES per square centimeter,the unit being the Potie, which is equal bone dyne-second per square centimeter.

VISCOSITY, DYNAMIC (Also called coeff-icient of molecular viscosity, coe@ient ofviscosity) — A coefficient defined as theratio of the SHEARING STRESS to theSHEAR of the motion. It is independentof the velocity distribution, tbe dimensionsof the system, etc., and for a gaa it is inde-pendent of pressure except at very lowpressures. While the dynamic viscosity ofmost gases increases rapidly with increas-ing temperature, that of most liquids, in-cluding water, decreases rapidly with in-creasing temperature. (AMS ) ●

VISCOSITY, KINEMATIC — A coefficientdefined as the ratio of the DYNAMIC

139

A


VISCOSITY of a fluid to its density. Thekinematic viscosity of most gases increaseswith increasing temperature and decreas-ing pressure. For dry air at O“ C., the kine-matic viscosity is about 0.13 square centi-meters per second. (AMS ) *

VISIBILITY, n.— In United States weatherobserving practice, the greatest distancein a given direction at which it ie just pos-sible to see and identify with the unaidedeye (a) in the daytime, a prominent darkobject againat the sky at the horizon, and(b) at ni~ht, a known, preferably unfo-cueed, moderately intense light source.(AMS)*

VISIBILITY CHART — Map or photographshowing which areas can be seen, andwhich cannot be seen, from a given ob-aeryation point. (AD)

VISI~LE RADIATION — Electromagneticradiation lying within the wavelength in-terval to which the human eye is sensitive,the spectral interval from approximately0.4 to 0.7 microns (4000 to 7000 ang-stroms). (AMS)*

VISIBLE SPECTRUM — That portion ofthe electromagnetic spectrum occupied bythe wavelength of VISIBLE RADIA-TION. (AMS)

VOID RATIO — The ratio of volume of voidsto the volume of solid aibstance in anymaterial consisting of solid m~terial andvoids. (S&V )

VOLATILIZATION, n.— The evaporation orchanging of a substance from liquid tovapor. (YA)

VOLCANIC ASH — The unconsolidated fine-grained material thrown out in volcaniceruptions. It consists of minute fragmentsof glass and other rock materia!, which incolor and general appearance may resem-ble organic ashes. (S&V) ●

VOLCANIC BRECCIA — More or less in-durated volcanic rocks consisting chiefly ofangular ejects 32 mm or more in diameter.


(s&v) ●

VOLCANIC CINDERS — Uncementeti vol-canic fragments that range from 4 to ~-mm in diameter. Such fragments are usual-ly glassy or vesicular. (S&V)

VOLCANIC CONE — A cone-shaped emi-nence formed by volcanic discharges. (GS)

VOLCANIC ERUPTION — The appearance,usually sudden and violent, at the surfaceof the earth of lava, ash, vapor, steam, andother materials from a volcano. (S&V)

VOLCANIC NECK — The solidified materialfilling a vent or pipe of a dead volcano. Ifor when a volcanic neck has resisted degra-dation better than the mass of the moun-tain, it will stand alone as a column, tower,or crag of igneous rock. (GS)

VOLCANIC ROCKS—see IGNEOUSROCKS.

,VOLCANIC RUBBLE — An unconsolidatedaccumulation of volcanic fragments largerthan CINDERS.

VOLCANO, n.— A mountain that has beenbuilt up by the materials ejected from theinterior of the earth through a vent. (GS)

w

WADI, n.— Same as DRY WASH.

WALLOW COURSE – Wide trench tidiedwith a decontaminating chemical, usuallychlorinated hme mixed with mud. Vehic-les that have come in contact with chemi.cal agents are driven or wallowed throughthis trench so that they can be freed fromthe agents. Also called mud lime slurrycourse. (AD)

WASH, n.— 1. A DRY WASH. 2. Detritus(all\lvium) collected, carried, and depositedby the action of water. (GS)

WASTAGE, n.— 1. The process or processesby which glaciers lose substance. Wastageis usually considered as including wind ero-sion, corrosion, and calving as well as evap-oration and melting, but is sometimes used

140


as a synonym for ablation. 2. The amountof material lost .by this process. (ADT)

WASTELAND, n.— Land not suitable for,or capable of, producing materials or .qerv.ices of value. (SSS) *

WATER CONTENT—See MOISTURECONTENT.

WATERCOURSE, n.—l. A stream of water,(ND) 2. Anatural channeI through whichwater may or does run. (ND)

WATER EQUIVALENT OF S~OW—Amount of water that would be obtainedif the-snow should be completely me]ted.See SNOW DENSITY. (MH) *

WATER GAP — A pass in a mountain ridgethrough which a stream flows. (GS)

WATER LOSS — The difference between theaverage precipitation over a drainage basinand the water yield from the basin for agiven period. (MH) *

WATER SKY — Dark patches or etreaks onthe clouds due to the reflection of leadsand polynae, or a uniform black due to anopen sea in the vicinity of large areas ofice or snow covered land, Detai]~ of thearrangement of the ice can be seen clearlywhen low stratus clouds are present. (AD)

WATERSPOUT, n. - Usually, a TORNADOoccurring over water; rarely, a lesserwhirlwind over water, comparable in in.tensity to a DUST DEVIL over land.(AMS) *

WATER TABLE — The surface defined bythe upper limit of the ZONE OF SATURA.TION, or the surface of unconfined groundwater. (AMS ) *

WATER VAPOR — Water in vapor form;one of the most important of all constitu-ents of the atmosphere. Its amount varieswidely in space and time due to the greatvariety of both “sources” of EVAPORA.TION and “sinks” of CONDENSATIONthat provide active motivation to the HY.DROLOGIC CYCLE. (AMS) *

141


WATER YEAR — In referring to surface-water eupply, the 12-month period, October1 through September 30. The water yea7 isdesignated by the calendar year in whichit ends and which includes 9 of the 12months. (MH) *

WATER YIELD — The runoff from thedrainage basin, including ground-wateroutflow that appears in the stream plusground-water outflow that bypasses thegaging station and leaves the basin under-ground. Water yield is the PRECIPITA.TION minus the EVAPOTRANSPIRA.TION. (MH)

WAVE, n.– 1. An undulation or ridge on thesurface of a fluid. A wirrd wave is generat-ed by friction between wind and the fluidsurface. Ocean waves are produced princi-pally in this way. (ND)* 2. A disturbancepropagated in such a manner thst it mayprogess from point to point. An elecfro-mametic wave is produced by oscillationof an electric charge. (ND)* 3. A markedvariation from normal weather, as a hearwave or a cold wave. (ND)

WAVE-BUILT TERRACE — The coarserupper portion of a beach where the waveshave thrown the pebbles up in low ridgesparallel to the shore line and a few feetabove mean high water level. (S&V) *

WAVE-CUT TERRACE — A flat or gentlysloping surface, usually covered by shallowwater, which waves have cut by removalof bedrock or unconsolidated material.(s&v)

WAVE, DIFFRACTED — A wave whosefront has been changed in direction byan obstacle or other nonhomogeneity in amedium, otherwise than by refktion orrefraction. ( ASA)

WAVE GUIDE — A hollow rectangular orcylindrical tubing used as a special ,formof very high frequency transmission line,the dimensions of the tubing determiningthe wave length to be transmitted. (AFD)

WAVE INTERFERENCE — The phenome.non which results when waves of the same



or nearly the same frequency are super-posed and is characterized by a spatial ortemporal distribution of amplitude differ-ing from that of the individual superposedwaves. (ASA)

WAVE LENGTH (or WAVELENGTH)—In general, the mean distance betweenmaxima (or minima) of a roughly periodic’pattern. More specifically, wave length isthe least distance between particles movingin the same phase of oscillation in a wavedisturbance. The wave length is measuredalong the direction of propagation of thewave, usually from the midpoint of a crest(or trough) to the midpoint of the nextadjoining crest (or trough). (AMS)*

WAVE, LONGITUDINAL — A wave inwhich the direction of displacement ateach point of the medium is normal to thewave front. (SVH) i

WAVE, SHEAR — A wave in an elastic me-dium which causes an eIement of the me-dium to change its shape without a changeof volume. (SVH)

WAVE, TRANSVERSE — A wave in whichthe direction of displacement at each pointof the medium is parallel to the wave front.(SVH)

WAVE VELOCITY (Also called phase speed)— The speed of propagation of a point ofconstant phase (or PHASE ANGLE) of asimple harmonic wave component. Withreference to ocean waves, the terms wavevelocity or wave celerity are used morecommonly than phase speed. (AMS) ●

WBGT INDEX (Abbrev. for: WET BULB,GLOBE TEMPERATURE INDEX) - Ameasure of the seventy of a hot climateby taking into account relative humidityand radiant heat load as well as thedry-bulb temperature. The WBGT Index ismade up by weighting the wet-bulb tem-perature by 0.7 (for relative humidity),the black globe temperature by 0.2 (forradiant temperature), and the dry-bulbtemperature by 0.1 (shade temperature).

WEATHER, n.— 1. The state of the atmo-sphere, mainly with respect to its effectsupon life and human activities. (AMS) *2. As used in the making of surfaceweather observations, a category of indivi-dual and combined atmospheric phenomenawhich must be drawn upon to describe thelocal atmospheric activity at the time ofobservation. (AMS) *

WEATHER, v.t. – To expose to the atmos-phere. (AMS)

WEATHER CENTRAL — An organizationwhich collects, collates, evaluates, and dis-seminates meteorological information insuch manner that it becomes a principalsource of such information for a givenarea. (JD)

WEATHER CODE — Proforma code usedfor describing weather conditions. (AD)

WEATHER FORECAST — A prediction ofweather conditions at a poiant, along aroute, or within an area for a specifiedperiod of time. (JD)

WEATHERING, n.— The mechanical, chem-ical, or biological action of the atmosphere, ●hydrometeors, and suspended impurities onthe form, color, or constitution of exposedmaterial; to be distinguished from ERO-SION. (AMS) *

WEATHERING, ACCELERATED — Anartificial means used to accelerate andduplicate the effects of rain modified sun-light, etc.

WEATHER INTELLIGENCE - weatherinformation interpreted in relation to itseffects upon personnel, materiel and thearea of operations. (AD)

WEATHER MAP— A map showing weatherconditions prevailing or predicted over aconsiderable area. Usually, the map isbased upon weather observations taken atthe same time at a number of stations. (JD)

WEATHER STATION — An installation orfacility which provides meteorological ob-servations and may also provide medium

142


‘e

e

.

range weather forecasts for limited geo-graphical areas on a full or part timeschedule. (AD)

WET-BULB DEPRESSION -The differencein degrees between tbe DRY-BULB TEM-PERATURE and the WET-BULB TEM-PERATURE. (AMS)

WET-BULB TEMPERATURE—The lowesttemperature to which air can be cooled atany given time by evaporating water intoit at constant pressure, when the heatrequired for evaporation is supplied by thecooling of the air. This temperature is indi.cated by a well-ventilated WET-BULBTHERMOMETER. (ND)

WET-BULB THERMOMETER — A ther-mometer having the bulb covered with acloth, usually muslin or cambric, saturatedwith water. (ND)

WET SNOW — In the International SnowClassification, snow which is saturated oralmost saturated with water. If free waterentirely fills the air spaces in the snow itis classified as “very wet snow.” (ADT)

WHALEBACK, n.— A tremendous sandridge built by movement of dunes over thesame path for long periods of time. Ridgesare elongated in plan and exhibit gentle,rounded crests, although one or more longi.tudinal dunes may be superimposed.

WHITE BODY — A hypothetical “body”whose surface absorbs no electromagneticradiation of any wavelength, i.e., one whichexhibits zero absorptivity for all wave-lengths; an idealization exactly opposite tothat of the BLACK BODY. (A!@”.

WHITECAP, n.— See BREAKER.

WHITE FROST “—See HOARFROST.

WHITEOUT, n.—A weather condition in thepolar regions in which no object casts ashadow, the horizon becomes indistinguish.able, and light-colored objects are verydifficult to see. Also called milky lueather.A whiteout occurs when there is completesnow cover, and the clouds are so thick


and uniform that light reflected by thesnow is about the same intensity as thatfrom the sky. (~”

WILLIWAW, n.—l. A sudden violent gust ofcold land air, common along mountainouscoasta of high latitudes. (AD) 2. A veryviolent squall in the Straits of Magellan.They may oetur in any month but are mostfrequent in winter. (AMS)

WIND, n.—Air in motion relative to the sur.face of the earth. Since vertical compo-nents of atmospheric motion are relativelysmall especially near the surface of theearth, meteorologists use the term to de-note almost exclusively the horizontal com-ponent. (A MS) ●

WINDBREAK, n. — A planting of trees,shrubs, or other vegetation, usually per-pendicular or nearly so to the principalwind direction, to protect soil, crops, home.steads, roads, etc., against the effects ofwinds, such as wind erosion and the drift.ing of soil and snow. (SSS)

WINDCHILL, n.— The combined coolingeffect of wind and air temperature onheated bodies. Windchill is expressed inkilogram calories per square meter perhour. (AD)

WIND COMPONENT INDICATOR -Devicewhich mechanically determines the rangeand deflection components of the computedwind that is equivalent to all true windsencountered by a projectile in flight. (AD)

WIND CORRECTION — Any adjustmentwhich must be made to allow for the effectof the wind; especially the adjustments tocorrect for the effect on a projectile inflight, on sound received by sound-ran’~nginstruments, and on aircraft flown by deadreckoning navigation. (AD) ●

WIN D CORRECTOR — A mechanical devicewhich computes the correction necessaryfor the effect of wind, used in sound rang-ing and artillery fire control. (AD)

WIND DRIFT—Shift in the apparent posi-

143


MlL-STD-l 16525 MARCH i 966

tion of a sound source or target observedby sound apparatus. Wind drift is causedby the effect of wind on sound waves whichchanges their direction and increases ordecreases sound lag. (AD)

WIND EROSION — The process of wearingaway a surface by wind action and theabrasion of wind-borne materials. (ADT)

WINDFALL, n.— 1. A tree uprooted orbroken off by wind. 2. An area on whichthe trees have been thrown by wind. (SAF)

WIND GAP — A pass or gap not occupiedby a, stream; an air gap. (GS)

WIND PRESSURE—The total force exertedupon a structure by wind. For a flat surfaceit consists of two factors, the first being thedynamic pressure exerted on the windwardside of the surface. The second factor isthe pres~ure decrease, or suction, producedon the leeward side of the surface. (A MS) *

WIND RESOLVING MECHANISM—A de-vice similar to a WIND COMPONENTINDICATOR, which is mounted on a de-flection board or is part of a computer, Itmechanically determines the range and de-fledion components of the ballistic wind.(AD)

WIND ROSE—Any one of a class of dia-grams designed to show the distribution ofwind direction experienced at a given loca-tion over a considerable period; it thusshows the prevailing wind direction.(AMS) ●

WIND SHEAR — A change in space of winddirection and magnitude. (JD)

WIND TEE — A large weather vane locatedon or near a landing field to show the di-rection of the wind or direction of thetraffic pattern around the field. (AD)

WIND TUNNEL — A tunnel through whicha stream of air is drawn at controlledspeeds for aerodynamic tests and experi-mentation. (AF)

WINTERIZATION, n.—The process of con-

verting equipment, especially changea inaccessories;, ~nstrumenk, or special instal-lations, for use in cold or very cold weather,as in the Arctic. (AD)

WIPE SAMPLE — A sample made for thepurpose of determining the presence ofremovable radioactive contamination on asurface. It is done by wiping, with slightpressure, a piece of soft filter paper overa representative area of surface.

x

XEROPHYTES, n.—Plants that grow in oron extremely dry soils or soil materials.(sss)

X-RADIATION (or X-RAYS) — Electro-magnetic radiation in the wavelengths, re-gion from about iOO to 0.1 Angstroms,which overlaps the ultraviolet region atlong x-ray wavelengths and the gamma rayregion at short x-ray wavelengths. Thedistinction is that x-rays and ultravioletradiation are produced by different proc-esses. See GAMMA RAY. ●

XYLOPHAGOUS, adj. – Eating, boring in,or destroying wood, said especially ofCerttin insect ]arvae, crustaceans, andmoUusks.

Y

YARDANGS, n. – Irregular ridges ormounds, commonly alternating withround-bottomed troughs, formed by winderosion of silt and clay, often of ancientPLAYA surfaces.

YELLOW PODZOLIC SOILS — Pedology.Formerly used for a zonal group of soilshaving thin organic and organic-minerallayers over grayish-yellow leached horizonsthat rest on yellow B horizons, developedunder coniferous or mixed coniferous anddeciduous forests in a warm-temperste towarm, moist climate. These soils are now

144


.,

MlL-STD-l 16S25 MARCH 196S

‘w combined into the Red.yellow ped~Oli~ actly nullified or counterbalanced by iner-group. (YA) tial force. (AF)”

YIELD, n.— See NUCLEAR YIELDS. ZONAL, adj.— In meteorology, latitudinal;

YOUNG ICE — Ice that has formed so re- easterly or westerly; opposed to mem”di-

cently that it is not strong enough for a end. (AMS)

man to walk on. Frequently referred to inconnection with LEADS. (AD)

ZONAL SOIL — F’edology. 1. A soil charac-teristic of a large area or zone. (SSS) 2.One of the three primary subdivisions

z(orders) in soil classification as used in theUnited States. (SSS)

ZENITH, n.— The point on the celestialsphere directly above the observer’s posi-tion. (AF)

ZEPHYR, n.— A warm, gentle breeze, espe-cially one from the west. (ND)

ZERO CURTAIN — The layer of ground be-tween tire ACTIVE LAYER and the per-mafrost where the temperature O°C

ZONE OF AERATION — The region of soilor rock above a WATER TABLE wherethe pore spaces contain air as well as water,(AMS)

ZONE OF MAXIMUM PRECIPITATION—In a mountain region, the belt of elevationat which the annual precipitation is great-

. est. (AMS) ●

(32”F) lasts for a considerable time duringthe freezing and thawing of overlying

ZONE OF SATURATION—The soil or rockbeneath the WATER TABLE. Pore spacesground. (ADT)

‘9

in the zone of saturation are filled withZERO GRAVITY — The complete absence of water, in contrast to the pore spaces above

gravitational effwtg, existing when the the water table which may contain con-gravitation attraction of a pr;mary is ex- siderable air. (AMS)

Cuatodiana: Prep*ring activity:

Army-GL Arnry-GL

N.svy-AS

Air Force-l 1 Project No. MISG0346

Review activities:

Army-CE, EL, hiD, Ml, MU,MU,WC

Nsvy-.AS, MS

Air Force-n

User activities:

Army-AT, AV

a Navy-CG, MC, OS, SA, SH

143


AIL-STD-1 I 6525 MARCH 1968

APPENDIX

10. Explanation of sources.The sources listed below are grouped into

three categories. The first consists of officialglossaries of major elements of the Depart-ment of Defense. Definitions of environmentalterms that have been standardized by any ofthese elements generally take precedence overother definitions in Department of Defenseusage. The second category consists of othersources having some degree of official accept-ance by Governmental agencies or profession-al organizations. These include glossswies thathave been published by Department of De-fense agencies for less than Department-wideuse, glossaries published by other Govern-mental agencies, and glossaries that havebeen adopted for use within professions thatdeal with environmental sciences or engineer-ing. Many definitions have been borrowgdfrom these sources for use in the presentGlossary, but explanations and notes accom-panying the definitions in the original worksare generally omitted here. The third cate-gory consists of sources to which the readeris referred for terms not included in. thisGlossary or for alternative meanings that arenot given her:. Some of the works in thiscategory are references of a general naturethat treat large segments of science or tech-nology; others are standard references forfields marginal to the environmental sciencesbut having some relationship to the work ofthe environmental scientist or engineer. Stillothers are either compilations of diverse usesof terms for which preferred definitions arenot specified or are dictionaries reflecting thepredilections of an individual author ratherthan the officially adopted decisions of anorganized group or profession.

For convenience in identifying the author-ities for definitions included in this MilitaryStandard, references under the fiist two cate-gories are listed under the name of thesponsoring organization or agency rather thanthe editor or author; references in the thirdcategory are fisted in the usual bibliogmphic

style. Letters preceding each entry are fistedin identifying symbol by which it is referredto in the body of the Glossary. Definitions forwhich no source is cited in this Glossary arebased on the draft Environmental Terrrrinol-ogy prepared by the Department of the Na\~in 1963, or on comments submitted bymifitary agencies that reviewed various draftsof this Militasy Standard.

Definitions in this Glossary that are iden-tified by the symbols ASA, ECS, SAF, SSS,S&V, and SVH are from copyright sourcesand should not be reprinted without per-mission of the pubfishers and copyrightholders named in Section 10.1.2. The formerAmerican Standards Association, publisher ofAcoustical Terminology, is now the UnitedStates of America Standards Institute, 10 East40th Street, New York 10016. Copyright ofthe Glossary of .Soi/ Science Terms (SSS) isheld by the American Society of Agronomy,677 South Segoe Road, Madison, Wisconsin53711.

10.1 Biblio.qruphy

10.1.1 Principal Departmmt of Defemesources

JD—Joint Chiefs of Staff, Dictionary ofUnited States Military Terms forJoint Usage, JCS Pub. 1, G.P, O.,Washington, D.C., I Jan 1966.

AD—Department of the Army, Diction.ary of United States Army Terms,Army Regulation 320-5, Washing.ton, D.C., April 1965.

AF—Department of the Air Force. AirForce GIOSSaTY of StandardizedTerms and Definitions, Air ForceManual No. 11-1, Washington,D.C., 1 May 1965.

LND—Department of the Navy. Naviga.gation Dictionar~, H,O. Pub. 220,Washington, D.C., 1956.

146


s,;.!.

NOO—Department of the Navy. Glossarvof Oceanographic Terms, NavalOceanographic Office, SP-35, 2d cd.,Washington, D.C., 1966.

10.1.2 Other quoted sources

ADT—Arctic, Desert, Tropic InformationCenter, Research Studies Institute,Air University. G1OSSQTZIof Arcticand Subarctic Terms, ADTIC Pub.A-105, Maxwell AFB, Ala., Sept1956.

AFD—Air University, Research StudiesInstitute. The U.S. Air Force Dic-

tionary, edited by W. A. Heflin, AirUniversity Press, 1956.

AMS—American Meteorological Society.GtossarV of Meteorology, edited byR. B. Huschke, Boston, Mass., 1959

AR—Army Regulation 705-15, Researchnmf Development of Materiel,Overation of Materiel under Ez-t>:eme Conditiom of Environment,Washington, D.C., 4 Ott 1962.

ASA— American Standards Association,Acoustical Society of America,Standard S1. 1-1960, AcousticalTerminology (Including Shock andVibration), New York, 25 May1960.

BR—Bureau of Rcdamation, US. De-partment of the Interior. EarthManual, Denver, Colorado, July1960.

ECS—Electro Chemical Society, Inc. Glos-sary of Terms Used in Corrosion,in: The Corrosion Handbook, editedby H. H, Uhlig, John Wiley & Sons,New York, 1948.

FM-f-l.S. Department of the Army, FM30-10. ?’errain InteUigmrcc, Wash.ingt.on, D.C., October 1959.

GS—Geological Survey, U.S. I.@+rt-ment of the Interior. Glossary of

MN-STD-1 16S25 MARCH 196S

Names for Topographic Forms, in:Topo,yruphir Instructtorw, Book 6,Part 6A, Washington, August 1954.

IG—U.S. Navy Electronics Laboratory.Ice Glossary, compiled by R. J..Boyle, San Diego, Calif., June 1965.

lSO—International Standards Organiza-tion, Technical Committee 108. Vi.fwat!on and Shock Terminology(Draft 2), 1965.

MH—Geolw;ical Survey, U.S. Depart-mentof theInterior .General Intro-duction and Hydrologic Definitions,by W. B. Langbein and Kathleen T.Iseri, in: Manual of ffVdrology.’Part 1. General Surface-WaterTechniques, Geological Survey W-ter-SuppIy Paper 1541-A, G.P. O.,Washington, 1960.

NAS—N9tional Academy of Sciences,National Research Council. G/os-‘sarrjof Pedologic (Soils) and Land-fornr Terminology for Soil Engi-neers, Highway Research BoardSpecial Report 25, Washington,DC., 1957.

NASA—National Aeronautics and SpaceAgency. Aeronautical Dictionary,by Frank D. Adams, G.P. O., Wash-ington, D.C., 1959.

NRCC—National Research Council of Can-ada. Techniques of Road Construc-tion over Oraanic Terrain. by 1. C.MacFarlane~ Technical Paper 45,Div. of Building, NRCC, Ottawa,1956.

SAF—Society of American Foresters,ForestrV Terminology:A Glossargof Tech?l.ical Ter’ms Used in For-est~y, 3rd edition, Washington,D.C., 1958.

SSS—Soil Science Society of America,Committee on Terminology. Glos-sary of Soil Science Terms, in:

147



PrOceedinOs 0/ the Soil .Scieuce S’o-ciety. of America, v. 29, pp. 330-351,May-June 1965.

S&V—Colorado Scientific Society. Glos-sar~ of Selected Geologic ‘Termswith special ~efercnm to their useinengineering, by W. L. Stokes andL J. Varnes, Denver, Colorado,1955.

SV?l-Shock and Vibration Handbook,edited by C. M. Harris and C. E.Creole, McCraw-Hill, New York,1961. Copyright by McGraw-HillBook Co., Inc.

WES—U.S. Army Engineer WaterwaysExperiment Station, Corps of Engi.neera, Vicksburg, .Mississippi. Un.published comments, January 1968.

WMO—World Meteorological Organization.[nterrmtimtal Cloud Atlas, vol. I,Geneva, 1956.

YA—U.S. Department of Agriculture.Soil, the 1957 Yearbook of Agri-crd.ture, G.P. O,, Washington, D.C.,1967.

10.1.3 Other ?efe~ences

Allen, William H. (cd.). Dictionar~ ofTechnical Terms for Ae~ospaceUse, NASA SE’-7, G.P. O., Washing-

. irrgton, D.C., 1965.

American Geological Institute. GJossaryof Geology and Related $m’eyces,with Supplement, 2nd cd., NAS-NRC, Washington, D.C., 19$0.

American Society of Mechanical Engi-neers, National Research Council.A G[OSsamJ of Terms in NuclearScience and Technology, AmericanSociety of Mechanical Engineers,New York, 1957.

Ballentyne, D. W. G., and L. E. Q. Walk-er. A Dictionar7J of Named E/jects

and Laws, 2nd edition, The Mac-millan Company, New York, 1961.

Bennett, H. Coucise Chemical and Tech-nical Dictionary, 2nd edition, Chem-ical Publishing Company, NewYork, 1962.

Flood, W, E., and M. West. Dictiomrvof Scientific and Technical Words,Longmana, Green and Company,New York, 1952.

Freiberger, W, F. (editor-in-chief). TheInternational Dictionary of Ap-plied Mathematics, D. Van Nest.rand Company, Inc., Princeton,N.J., 1960.

Gaynor, Frank. Concjse Dictionary ofScience, Philosophical Library, NewYork, 1959.

Gray, H. J. Dictionary of Physics, Long-mans, Green and Company, NewYork, 1958.

Hanson, Herbert C. Dictionary of Eco/-og~, Philosophical Library, NewYork, 1962,

Henderson, I. F., and W. D. Henderson.A Dictionary of Biological Terms,8th edition, D. Van Nostrand Com-pany, Inc., Princeton, N. J.. 1963.

Henderson, I. F. and W. D. Henderson.A Dictionar3 of Scientific Tw’ms,7th edition, D. Van Nostrand Com-pany, Inc., Princeton, N. J., 1960.

Jacobs, M. B., M. J. Gerstein, and W. G.Walter. Dictio?tanj of Microbiology,D. Van Nostrand Company, Inc.,Princeton, N. J., 1957.

James, Glenn, and R. C. James (editors).Mathematics Dictionary, lfultilin-gua! edition, D. Van Nostrand Com-pany, Inc., Princeton, N. J., 1959.

Michels, Walter C, (editor-in-chief), TheInternational Dictionary of Physicsarrd E/ectrowics, 2nd edition, D.

148

\ ,“,

..+,


Van Nostrand Company, Inc.,Princeton, N.J., 1961.

Monkhouse, F. J. A Dictionary of Geog-raphy, Edward Arnold, Ltd., Lon-don, 1965.

Rose, Arthur and Elizabeth (editors).The Condensed Chemical Diction-ar~, 6th edition, Reinhold Publish.ing Corporation, New York, 1961.

Snell, Walter H. and Ester A. Dick. AGlossary of Mgcology, HarvardUniversity Press, Cambridge, 1957.


Stamp, L. Dudley (editor), prepared bya Committee of tbe British Asso-ciation for the Advancement of Sci-ence. A Glossary of Geographical‘1’errrzs,John Wiley and Sons, Inc.,New York, 1961.

Winburne, John N. (editor-in-chief). ADictionary of Agr+ccdtural and

Allied Terminology, Michigan State

University Press, East Lansing,Michigan, 1962.

149


Documents

GLOSSARY OF . ENVIRONMENTAL TERMS(TERRESTRIAL)everyspec.com/MIL-STD/MIL-STD-1100-1299/download.php?... · Glossary of Environmental Terms (Terrestrial) 1. SCOPE The terms included