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h...h...PowerPointPowerPoint/...//.../precipitationprecipitation..ppttptpt

Have you ever just looked Have you ever just looked at clouds?at clouds?

Wh d Wh d Why do we Why do we have clouds?have clouds?Why are there Why are there different different different different shapes?shapes?What can they What can they tell us about tell us about tell us about tell us about the weather?the weather?

Take Good Notes!Take Good Notes!Take Good Notes!Take Good Notes!

There will be There will be There will be There will be a quiz on a quiz on thi thi this this informationinformation

Understanding CloudsUnderstanding CloudsUnderstanding CloudsUnderstanding Clouds

Clouds form asClouds form asClouds form as Clouds form as warm air is warm air is forced upwardforced upwardAs the air isAs the air isAs the air is As the air is forced upward, forced upward, it expands and it expands and coolscoolscoolscools

Understanding CloudsUnderstanding CloudsUnderstanding CloudsUnderstanding Clouds

As the air coolsAs the air coolsAs the air cools, As the air cools, the relative the relative humidity humidity reaches 100%reaches 100%reaches 100%reaches 100%For more information on For more information on Relative Humidity click Relative Humidity click ☼☼e at e u d ty c ce at e u d ty c c ☼☼

Water vapor begins to condense Water vapor begins to condense in tiny drops around nuclei. in tiny drops around nuclei. y py p

Nuclei are small particles of dust, Nuclei are small particles of dust, salt and smoke in the salt and smoke in the salt, and smoke in the salt, and smoke in the

atmosphereatmosphere

Cloud TypesCloud TypesCloud TypesCloud Types

There are There are many many different different different different cloud typescloud typesypyp

Cloud TypesCloud TypesCloud TypesCloud TypesCan you think Can you think of the two of the two main ways main ways main ways main ways that clouds that clouds

l ifi d? l ifi d?are classified?are classified?ShapeShape HeightHeight ShapeShape, , HeightHeight, , and and

i i sometimes sometimes RainRain CapacityCapacity

By Shape!By Shape!By Shape!By Shape!There are three main cloud There are three main cloud There are three main cloud There are three main cloud

types that are based on shapetypes that are based on shapeThink you know any of them?Think you know any of them?

StratusStratusCumulusCumulusCumulusCumulus

CirrusCirrus

Stratus CloudsStratus CloudsStratus CloudsStratus CloudsStratus Stratus clouds form clouds form a smooth a smooth a smooth, a smooth, even sheeteven sheetThey usually They usually form at low form at low form at low form at low altitudesaltitudes

Stratus CloudsStratus CloudsStratus CloudsStratus Clouds

When air is When air is cooled and cooled and condenses near condenses near the ground, a the ground, a stratus cloud stratus cloud know as _______ know as _______ formsformsKnow the Know the name?name?

Cumulus CloudsCumulus CloudsCumulus CloudsCumulus CloudsThese are These are These are These are masses of masses of puffy white puffy white puffy, white puffy, white clouds, often clouds, often with flat baseswith flat baseswith flat baseswith flat basesThey form They form

hen air hen air when air when air currents risecurrents rise

Cumulus CloudsCumulus CloudsCumulus CloudsCumulus CloudsTh b Th b They can be They can be associated associated with both fair with both fair weather weather weather weather and…….when and…….when h llh llthey get really they get really

tall !tall !______

Thunderstorms!Thunderstorms!Thunderstorms!Thunderstorms!

Cirrus CloudsCirrus CloudsCirrus CloudsCirrus CloudsCi l d Ci l d Cirrus clouds Cirrus clouds are high, thin, are high, thin, white, white, feathery feathery feathery feathery clouds clouds containing containing ice ice crystalscrystalsyy

Cirrus CloudsCirrus CloudsCirrus CloudsCirrus CloudsCirrus clouds Cirrus clouds are usually are usually associated associated associated associated with fair with fair weather, but weather, but they may they may they may they may indicate indicate

hi hi approaching approaching stormsstorms

By HeightBy HeightBy HeightBy HeightTh fi f l d Th fi f l d The prefix of cloud names can The prefix of cloud names can describe the height of cloud describe the height of cloud

basesbasesCirro: High clouds abo e Cirro: High clouds abo e Cirro: High clouds above Cirro: High clouds above

6000m6000m

By HeightBy HeightBy HeightBy Height

Alto: Middle elevation clouds Alto: Middle elevation clouds between 2000 to 6000mbetween 2000 to 6000m

Strato: Low level clouds below Strato: Low level clouds below 2000m2000m

Rain CloudsRain CloudsRain CloudsRain CloudsNi bNi bNimbusNimbusclouds are clouds are dark clouds dark clouds associated associated associated associated with with precipitationprecipitation

Rain CloudsRain CloudsRain CloudsRain CloudsWhen a nimbus When a nimbus When a nimbus When a nimbus cloud is also a cloud is also a towering towering towering towering cumulus cloud, cumulus cloud, it’ ll d it’ ll d it’s called a it’s called a cumulonimbus cumulonimbus cloudcloud

Cirrus Cl dClouds

CumulostrCumulostratus

Clouds

Ready for a quick review?Ready for a quick review?Ready for a quick review?Ready for a quick review?

1 Cl d f h th 1 Cl d f h th 1. Clouds can form when the 1. Clouds can form when the relative humidity reaches ____%relative humidity reaches ____%2. In order for clouds to form, 2. In order for clouds to form,

ater apor begins to condense ater apor begins to condense water vapor begins to condense water vapor begins to condense around ____of dust, salt, and around ____of dust, salt, and smokesmoke

3. Clouds are classified by ____ 3. Clouds are classified by ____ d d i i d d i i and____ and sometimes rain and____ and sometimes rain

capacitycapacity4. Puffy, white clouds are called?4. Puffy, white clouds are called?5 Mid elevation clouds between 5 Mid elevation clouds between 5. Mid elevation clouds between 5. Mid elevation clouds between 2000 and 6000m2000 and 6000m

Let’s see how you did!Let’s see how you did!Let s see how you did!Let s see how you did!

11 1001001.1. 1001002.2. NucleiNuclei2.2. NucleiNuclei

3.3. Shape and heightShape and height4.4. CumulusCumulus

55 AltoAlto5.5. AltoAlto

Forms of Forms of PrecipitationPrecipitationForms of Forms of PrecipitationPrecipitationP i it ti (P i it ti ( ii hhPrecipitation (prePrecipitation (pre--sipsip--uhuh--taytay--shun) is any form of shun) is any form of taytay shun) is any form of shun) is any form of water that falls to the water that falls to the Earth's surfaceEarth's surface. .

Types of PrecipitationTypes of PrecipitationTypes of PrecipitationTypes of PrecipitationTh t f i it ti th t Th t f i it ti th t The type of precipitation that The type of precipitation that falls to the ground depends falls to the ground depends g pg pupon the formation process upon the formation process

d th t t f th d th t t f th and the temperatures of the and the temperatures of the environment between the environment between the environment between the environment between the cloud and the surfacecloud and the surface

Can you name the different Can you name the different types of precipitation?types of precipitation?

R iR iRainRainSnowSnowSnowSnowHailHailSleetSleet

Freezing RainFreezing RainFreezing RainFreezing Rain

RainRainRainRainRain develops when Rain develops when Rain develops when Rain develops when

growing cloud droplets growing cloud droplets g g pg g pbecome too heavy to become too heavy to

remain in the cloud and remain in the cloud and remain in the cloud and remain in the cloud and as a result, fall toward the as a result, fall toward the ,,

surface as rainsurface as rain

R i l R i l A th f lli A th f lli Rain can also Rain can also begin as ice begin as ice

As the falling As the falling snow passes snow passes

crystals that crystals that collect each collect each

through the through the freezing level freezing level collect each collect each

other to form other to form ll

freezing level freezing level into warmer into warmer

h fl kh fl klarge large snowflakessnowflakes

air, the flakes air, the flakes melt melt

Rain from snow!Rain from snow!Rain from snow!Rain from snow!

SnowSnowSnowSnowS i f d h i S i f d h i Snow is formed when ice Snow is formed when ice crystals form from water crystals form from water yyvapor that is in the clouds vapor that is in the clouds di tl b h d !di tl b h d !directly above your heads!directly above your heads!This process is called This process is called This process is called This process is called sublimationsublimation

HailHailHailHailHail is formed Hail is formed Hail is formed Hail is formed when updrafts when updrafts

i di dcarry raindrops carry raindrops upwards into upwards into extremely cold extremely cold areas of the areas of the areas of the areas of the atmosphereatmosphere

HailHailHailHailThere the There the There the There the raindrops raindrops merge and merge and merge and merge and freeze. When freeze. When the frozen the frozen the frozen the frozen clumps get to clumps get to heavy they fall heavy they fall heavy they fall heavy they fall to earthto earth

HailHailHailHailH il H il Hail can vary Hail can vary in size, from in size, from the size of a the size of a small stone to small stone to small stone to small stone to that of a that of a b b llb b llbaseball! baseball! So So be carefulbe careful

SleetSleetSleetSleetSleet is frozen raindrops Sleet is frozen raindrops Sleet is frozen raindrops. Sleet is frozen raindrops. Sleet begins as rain or snow Sleet begins as rain or snow and falls through a deep and falls through a deep layer of cold air that layer of cold air that layer of cold air that layer of cold air that contains temperatures below contains temperatures below f i th t i t th f i th t i t th freezing that exist near the freezing that exist near the surfacesurface..

SleetSleetSleetSleetR i th t f ll R i th t f ll Rain that falls Rain that falls through this through this extremely cold extremely cold layer has time layer has time layer has time layer has time to freeze into to freeze into

ll fll fsmall pieces of small pieces of iceice

Freezing RainFreezing RainFreezing RainFreezing RainF i i i f lli i th t F i i i f lli i th t Freezing rain is falling rain that Freezing rain is falling rain that cools below 0cools below 0°°C, but does not C, but does not turn to ice in the air turn to ice in the air The ater is “The ater is “supercooledsupercooled””The water is “The water is “supercooledsupercooled””

When the drops hit anything When the drops hit anything they instantly turn to ice!they instantly turn to ice!

11 Nuclei for the formation of rain Nuclei for the formation of rain 1.1. Nuclei for the formation of rain Nuclei for the formation of rain drops can be small particles of: A) drops can be small particles of: A) salt B) smoke C) dust D) all the salt B) smoke C) dust D) all the salt, B) smoke, C) dust, D) all the salt, B) smoke, C) dust, D) all the aboveabove

22 Whi h f th l d t i t Whi h f th l d t i t 2.2. Which of these cloud types is not Which of these cloud types is not based on the clouds shape: A) based on the clouds shape: A) t t B) i b C) l t t B) i b C) l stratus, B) nimbus, C) cumulus, stratus, B) nimbus, C) cumulus,

D) cirrusD) cirrus

33 Mid l ti l d b t Mid l ti l d b t 33. Mid elevation clouds between . Mid elevation clouds between 2000 and 6000m: A) nimbus, B) 2000 and 6000m: A) nimbus, B) alto, C) cirro, D) stratoalto, C) cirro, D) strato

44 This form of precipitation is This form of precipitation is 44. This form of precipitation is . This form of precipitation is supercooled: A) rain, B) snow, supercooled: A) rain, B) snow, C) sleet, D) freezing rainC) sleet, D) freezing rain

55 Thi f f i it ti Thi f f i it ti 5.5. This form of precipitation This form of precipitation stays frozen all the way to the stays frozen all the way to the ground: A) rain, B) snow, C) ground: A) rain, B) snow, C) sleet D) freezing rainsleet D) freezing rainsleet, D) freezing rainsleet, D) freezing rain

Let’s see how you did!Let’s see how you did!

The Answers!The Answers!The Answers!The Answers!1 D1 D1. D1. D2 B2 B2. B2. B3 B3 B3. B3. B4. D4. D4. D4. D5. B5. B

Weather ModificationWeather ModificationWeather ModificationWeather Modification

•• Weather modificationWeather modification is deliberate human is deliberate human intervention to influence atmospheric processes intervention to influence atmospheric processes that constitute the weather. that constitute the weather.

•• Weather modification falls into three categories:Weather modification falls into three categories:(1) the use of (1) the use of energyenergy to forcefully alter the weather, to forcefully alter the weather, (2) (2) modifying land and water surfacesmodifying land and water surfaces to change their to change their natural interaction with the lower atmosphere andnatural interaction with the lower atmosphere andnatural interaction with the lower atmosphere, and natural interaction with the lower atmosphere, and (3) triggering, intensifying, or redirecting (3) triggering, intensifying, or redirecting atmospheric atmospheric processes. processes.

Intentional Weather Modification Intentional Weather Modification TechniquesTechniques

•• The focus of intentional weather The focus of intentional weather modification using modern weather modification using modern weather ggtechnology is on:technology is on:

cloud seedingcloud seeding,,cloud seedingcloud seeding, , fog and cloud dispersalfog and cloud dispersal, , hail suppressionhail suppression andandhail suppressionhail suppression, and , and frost preventionfrost prevention

Cl dCl dCloud Cloud seedingseedingseedingseeding

2.3. Measurement of Rainfall 2.3. Measurement of Rainfall

RainfallRainfall andand otherother formsforms ofof precipitationprecipitation arearemeasuredmeasured inin termsterms ofof depthdepth thethe valuesvalues beingbeingmeasuredmeasured inin termsterms ofof depthdepth,, thethe valuesvalues beingbeingexpressedexpressed inin millimetersmillimeters..OneOne millimetermillimeter ofof precipitationprecipitation representsrepresents thetheOneOne millimetermillimeter ofof precipitationprecipitation representsrepresents thethequantityquantity ofof waterwater neededneeded toto covercover thethe landland withwith aa11mmmm layerlayer ofof water,water, takingtaking intointo accountaccount thatthatyy ,, ggnothingnothing isis lostlost throughthrough drainage,drainage, evaporationevaporation ororabsorptionabsorption..InstrumentInstrument usedused toto collectcollect andand measuremeasure thetheprecipitationprecipitation isis calledcalled raingaugeraingauge..

Rain:Rain:I i it ti i th f f t d f iI i it ti i th f f t d f i–– Is precipitation in the form of water drops of size Is precipitation in the form of water drops of size larger than 0.5 mm to 6mmlarger than 0.5 mm to 6mmThe rainfall is classified in toThe rainfall is classified in to–– The rainfall is classified in toThe rainfall is classified in to

Light rain Light rain –– if intensity is trace to 2.5 mm/hif intensity is trace to 2.5 mm/hModerateModerate –– if intensity is 2 5 mm/hr to 7 5 mm/hrif intensity is 2 5 mm/hr to 7 5 mm/hrModerate Moderate if intensity is 2.5 mm/hr to 7.5 mm/hrif intensity is 2.5 mm/hr to 7.5 mm/hrHeavy rain Heavy rain –– above 7.5 mm/hr above 7.5 mm/hr

Rain MeasurementRain MeasurementRain MeasurementRain Measurement

•• Rain the most common form of precipitation isRain the most common form of precipitation is•• Rain, the most common form of precipitation, is Rain, the most common form of precipitation, is probably the easiest to measure. probably the easiest to measure.

•• The most common instruments used to measureThe most common instruments used to measureThe most common instruments used to measure The most common instruments used to measure rain are:rain are:

the the standard rain gaugestandard rain gauge, which is read directly, and , which is read directly, and g gg g , y,, y,the the tipping bucket gaugetipping bucket gauge and and weighing gaugeweighing gauge, both , both of which record the amount of rain. of which record the amount of rain.

AAA A standastandard rain rd rain gaugegauge

Rainfall measurement…Rainfall measurement…

Precipitation gauge1 - pole

2 ll t2 - collector3 - support-galvanized g

metal sheet 4 – funnel

5 - steel ring 5 steel ring

1 N di 1. Non recording gauge

2. Recording gauge / graphic raingauge 2. Recording gauge / graphic raingauge

TheThe instrumentinstrument recordsrecords thethe graphicalgraphicalvariationvariation ofof thethe fallenfallen precipitation,precipitation, thethe totaltotalp p ,p p ,fallenfallen quantityquantity inin aa certaincertain timetime intervalinterval andandthethe intensityintensity ofof thethe rainfallrainfall (mm/hour)(mm/hour)..yy ( )( )ItIt allowsallows continuouscontinuous measurementmeasurement ofof thetherainfallrainfallrainfallrainfall..

The graphic rain gauge1-receiver2 floater 2-floater 3-siphon

4-recording needle5-drum with diagram6-clock mechanism

3. Tele3. Tele--rain gauge with tilting baskets rain gauge with tilting baskets

The teleThe tele--rain gauge is used to transmit rain gauge is used to transmit measurements of precipitation through measurements of precipitation through p p gp p gelectric or radio signals. electric or radio signals. The sensor device consists of a system withThe sensor device consists of a system withThe sensor device consists of a system with The sensor device consists of a system with two tilting baskets, which fill alternatively with two tilting baskets, which fill alternatively with water from the collecting funnel establishingwater from the collecting funnel establishingwater from the collecting funnel, establishing water from the collecting funnel, establishing the electric contact. the electric contact. The number of tilting is proportional to theThe number of tilting is proportional to theThe number of tilting is proportional to the The number of tilting is proportional to the quantity of precipitation quantity of precipitation hphp

TeleTele--rain gauge …… rain gauge ……

The tele-rain-gauge

1 - collecting funnel 2 - tilting baskets3 electric signal3 - electric signal

4 - evacuation

4. Radar measurement of rainfall 4. Radar measurement of rainfall

The meteorological radar is the powerful instrument The meteorological radar is the powerful instrument for measuring the area extent location andfor measuring the area extent location andfor measuring the area extent, location and for measuring the area extent, location and movement of rainstorm.movement of rainstorm.The amount of rainfall overlarge area can beThe amount of rainfall overlarge area can beThe amount of rainfall overlarge area can be The amount of rainfall overlarge area can be determined through the radar with a good degree of determined through the radar with a good degree of accuracyaccuracyThe radar emits a regular succession of pulse of The radar emits a regular succession of pulse of electromagnetic radiation in a narrow beam so that electromagnetic radiation in a narrow beam so that when the raindrops intercept a radar beam itswhen the raindrops intercept a radar beam itswhen the raindrops intercept a radar beam, its when the raindrops intercept a radar beam, its intensity can easily be known. intensity can easily be known.

Raingauge Network Raingauge Network

SinceSince thethe catchingcatching areaarea ofof thethe raingaugeraingauge isisveryvery smallsmall asas comparedcompared toto thethe arealareal extentextentyy ppofof thethe storm,storm, toto getget representativerepresentative picturepicture ofofaa stormstorm overover aa catchmentcatchment thethe numbernumber ofof

ii h ldh ld bb ll ibliblraingaugesraingauges shouldshould bebe asas largelarge asas possible,possible,ii..ee.. thethe catchmentcatchment areaarea perper gaugegauge shouldshouldbebe smallsmallbebe smallsmall..ThereThere areare severalseveral factorsfactors toto bebe consideredconsideredtoto restrictrestrict thethe numbernumber ofof gaugegauge::toto restrictrestrict thethe numbernumber ofof gaugegauge::–– LikeLike economiceconomic considerationsconsiderations toto aa largelarge extentextent

TopographicTopographic && accessibilityaccessibility toto somesome extentextent–– TopographicTopographic && accessibilityaccessibility toto somesome extentextent..

Raingauge Network….. Raingauge Network…..

WorldWorld MeteorologicalMeteorological OrganizationOrganization (WMO)(WMO)WorldWorld MeteorologicalMeteorological OrganizationOrganization (WMO)(WMO)recommendationrecommendation::–– InIn flatflat regionsregions ofof temperate,temperate, MediterraneanMediterranean andand tropicaltropical

zoneszonesIdealIdeal 11 stationstation forfor 600600 –– 900900 kmkm22

AcceptableAcceptable 11 stationstation forfor 900900 –– 30003000 kmkm22AcceptableAcceptable 11 stationstation forfor 900900 30003000 kmkm

–– InIn mountainousmountainous regionsregions ofof temperatetemperate ,, MediterraneanMediterranean andandtropicaltropical zoneszones

IdealIdeal 11 stationstation forfor 100100 –– 250250 kmkm22

AcceptableAcceptable 11 stationstation forfor 250250 –– 10001000 kmkm22

–– InIn aridarid andand polarpolar zonezoneInIn aridarid andand polarpolar zonezone11 stationstation forfor 15001500 –– 1010,,000000 kmkm22

1010 %% ofof thethe raingaugesraingauges shouldshould bebe selfself recordingrecording totog gg g ggknowknow thethe intensityintensity ofof thethe rainfallrainfall

Weather Station

Placement of Rain GaugesPlacement of Rain GaugesPlacement of Rain GaugesPlacement of Rain Gauges

Gauges are affected by wind pattern, eddies, trees and Gauges are affected by wind pattern, eddies, trees and th it lf th f it i i t t t h thth it lf th f it i i t t t h ththe gauge itself, therefore it is important to have the the gauge itself, therefore it is important to have the gauge located and positioned properly.gauge located and positioned properly.

• 1m above ground level is standard -all gauges in a catchment should be the same height

• 2 to 4 times the distance away from an isolated object (such as a tree or building) or in a forest a clearing ( g) gwith the radius at least the tree height or place the

gauge at canopy level

Placement of Rain GaugesPlacement of Rain Gaugesgg

shielded to protect gauge in windy sites shielded to protect gauge in windy sites or if obstructions are numerous they will reduce the windor if obstructions are numerous they will reduce the windor if obstructions are numerous they will reduce the windor if obstructions are numerous they will reduce the wind--

speed, turbulence and eddiesspeed, turbulence and eddies..

Raingauge with Raingauge with wind guardsg

Placement of Rain GaugesPlacement of Rain Gauges••For sloping ground the gauge should be placed with the For sloping ground the gauge should be placed with the opening parallel to the groundopening parallel to the groundTh i f ll t h l (Th i f ll t h l ( 33)) i th di id d b thi th di id d b th••The rainfall catch volume (mmThe rainfall catch volume (mm33) ) is then divided by the is then divided by the

opening area that the rain can enteropening area that the rain can enter

Number and Distribution of GaugesNumber and Distribution of GaugesNumber and Distribution of GaugesNumber and Distribution of Gauges

Need to consider:Need to consider:size of area size of area prevailing storm type prevailing storm type form of precipitationform of precipitationt ht htopographytopographyaspectaspectseasonseasonseasonseason

Distribution of GaugesDistribution of Gaugesgg

The The distributiondistribution of gauges of gauges should not be randomshould not be random. . onl fi ed characteristics of areas can be sampledonl fi ed characteristics of areas can be sampled–– only fixed characteristics of areas can be sampled only fixed characteristics of areas can be sampled randomly. Random events randomly. Random events must must be sampled by a be sampled by a systematic arrangement of sampling pointssystematic arrangement of sampling points

Practical considerations of access and exposure mean Practical considerations of access and exposure mean that some pragmatism is required in designing athat some pragmatism is required in designing athat some pragmatism is required in designing a that some pragmatism is required in designing a network. network.

–– It is useful to locate gauges so thatIt is useful to locate gauges so that isohyetal mapsisohyetal maps can can be drawn Some gauges need to be near or outside thebe drawn Some gauges need to be near or outside thebe drawn. Some gauges need to be near, or outside the be drawn. Some gauges need to be near, or outside the catchment boundary in order to cover the catchment catchment boundary in order to cover the catchment completely.completely.

Number of GaugesNumber of Gaugesgg

Depends on Storm typeDepends on Storm type

Cyclonic stormsCyclonic storms (large areas, low intensities) (large areas, low intensities) --small small number of gauges may be O.K.number of gauges may be O.K.g g yg g y

Convective stormsConvective storms (local, intense, uneven (local, intense, uneven distribution)distribution) denser network needed Convectivedenser network needed Convectivedistribution) distribution) --denser network needed. Convective denser network needed. Convective storms may have seasonal dominance storms may have seasonal dominance --need to need to consider this as well.consider this as well.

OrographicOrographic rainfall due to mountains (not fronts) rainfall due to mountains (not fronts) --may may need denser network than flatter area.need denser network than flatter area.