Dr. R.A. Bartholomew - Civil Air Patrol, New Jersey Wing1 Cadet Phase I & II Aerospace Dimensions Air Environment (Module 3) Session 1: Chapter 1 ‘Air

Dr. R.A. Bartholomew - Civil Air Patrol, New Jersey Wing 1

Cadet Phase I & IICadet Phase I & IIAerospace DimensionsAerospace Dimensions

Air Environment (Module 3)Air Environment (Module 3)

Session 1: Chapter 1 ‘Air Circulation’ Chapter 2 ‘Weather Elements’

Session 2: Chapter 3 ‘Moisture and Clouds’ Chapter 4 ‘Weather Systems and Changes’

(ONLY for all Cadets that have not yet passed corresponding AE test, and Cadet Mentors)


Air CirculationAir Circulation

RadiationRadiation - a method of Heat Transfer This is the ONLY way heat can travel in a vacuum, and

is therefore how the Sun heats the Earth About 65% of the sun’s energy gets past the clouds

15% is absorbed by the atmosphere, the remaining 50% is remaining 50% is absorbed at the Earth’s surfaceabsorbed at the Earth’s surface

Heat and Pressure differences in the atmosphere, caused by Solar Heating are what causes weather

Heating and Cooling of the atmosphere also evaporates/condenses water vapor, causing clouds, rain, snow, and hail

Temperature and Pressure Changes also affect air density, which directly affects LIFT (remember Module 1?)


Air CirculationAir Circulation

Rotation and Revolution The Earth Revolves around the sunEarth Revolves around the sun once every 365

days (approx.) The Earth also Rotates, tilted at an angle of 23.5°Earth also Rotates, tilted at an angle of 23.5°

Revolution and Rotation together cause the seasons, and different weather patterns at different latitudes

Tilted towards the sun = long day Tilted away from the sun = short day Sun tracking along equator = day/night of equal length

– Autumnal EquinoxAutumnal Equinox: Equal length Day/Night (Fall - Sept 22/23)

– Vernal EquinoxVernal Equinox: Equal length Day/Night (Spring - Mar 21/22)

– Summer SolsticeSummer Solstice: Longest Day (June 21/22)

– Winter SolsticeWinter Solstice: Shortest Day (Dec 21/22)


Air CirculationAir Circulation Coriolis effectCoriolis effect: Since the Earth is rotating Counter-Clockwise,

anything travelling from North to South will be deflected WEST of the intended destination, if the fact that the earth is moving under them, is not accounted for

CirculationCirculation Uneven heating (e.g. equator and poles) causes pressure

differences, which result in movement of air Air is heated at the equator,

rises, then heads north or south, eventually cooling, and then much of it returns to the equator This creates the ‘Trade WindsTrade Winds’,

between 0° and 30° Lat. and an area of calm (rising) wind at the equator, called the ‘DoldrumsDoldrums’


Air CirculationAir Circulation Other predictable Wind patterns include:

Prevailing WesterliesPrevailing Westerlies, are cooling air moving towards the poles between 30° and 60° latitude

Above 60° latitude cooling and descending polar air forms Polar EasterliesPolar Easterlies

VERY large Temperature and Pressure differences, high up (in the Troposphere) cause special high speed winds called Jet StreamsJet Streams These travel in a band around the earth at between 100

and 300 MPH There are 4 jet streams, one of

which is over the United States Ours is at 30,000 to 35,000 ft, and

travels West to East, dipping South over the Mid West (but it moves!)


Air CirculationAir Circulation Important Terms (Quiz):

Autumnal Equinox Equal length Day/Night

(Fall - Sept 22/23)

Vernal Equinox Equal length Day/Night

(Spring - March 21/22)

Summer Solstice Longest Day (June 21/22)

Winter Solstice Shortest Day (Dec 21/22)

Coriolis Effect Jet Stream Radiation Revolution (of Earth

around Sun) How long does it

take?

Rotation (of Earth) What angle is the

earth’s axis tilted at?


Weather ElementsWeather Elements

Wind ‘A body of air in motionA body of air in motion’ Wind is defined by its Direction and SpeedDirection and Speed

e.g. Easterly (FROM the East) at 20 knots 1 knot = 1.1 MPH

The Beaufort ScaleBeaufort Scale (0 to 12) defined different wind strengths, by describing visible effects for different Wind Speeds

Wind can make the air feel colder than it is - this effect is called Wind ChillWind Chill The wind is removing the warm air from around your body, and

speeding heat loss A chart can be used to determine the wind chill Flying into wind increases lift, flying with the wind increases

speed, flying cross-wind pushes you off course.


Weather ElementsWeather Elements MicroburstMicroburst

A very strong, very fast moving downdraft, often from a thunderstorm, resulting in extreme turbulence

Temperature Temperature is the result of Heating, and is measured in degrees

Fahrenheit (°F) or Celsius/Centigrade (°C) Conversion: F = (1.8xC)+32 C=(F/1.8)-32

no need to memorize these equations Water Boils at 212°F and Freezes at 32°F (100 & 0 °C) HeatHeat is defined as ‘the total ‘the total EnergyEnergy of all Molecules (illustrated by of all Molecules (illustrated by

their motion) within a substance’their motion) within a substance’ Temperature is therefore defined as ‘a measure of molecular motion, ‘a measure of molecular motion,

using a man-made scale’using a man-made scale’ Heat, and therefore Temperature affects air Pressure and Density,

and is therefore VERY important information for Pilots e.g. high temperature = lower density = LESS LIFT


Weather ElementsWeather Elements

Pressure A gas pressing on another, or a surface results in Pressure Atmospheric PressureAtmospheric Pressure is the effect of air pushing down on

the Earth’s surface As molecules collide, movement results Measurement of Atmospheric Pressure:

Mercury BarometerMercury Barometer - Accurate, Reliable and Stable, used by Scientists

Aneroid BarometerAneroid Barometer - Fast and Easy to Read, but not particularly accurate

Aneroid BarographAneroid Barograph - Provides a permanent record of pressure changes, using a pen and a revolving drum of paper

Atmospheric Pressure affects air density, and differences causes bodies of air to move, thus creating wind.


Moisture and CloudsMoisture and Clouds

Moisture Moisture is Water in Solid (Ice), Liquid (Water), or Gaseous

(Vapor) form The air can only hold a limited amount of water vapor, when is

contains the maximum amount, it is SaturatedSaturated Saturation depends on temperature, the temperature at which

the air WILL become saturated is called the Dew PointDew Point Add more moisture, or decrease the temperature BELOW the

Dew Point, and CondensationCondensation (conversion to liquid) occurs Clouds and Fog are both forms of Condensation

Humidity describes the amount of moisture in the air The normal measure is Relative HumidityRelative Humidity, which is the % of

saturation which has been reached, e.g. 70%

Fog - mass of water droplets in suspensionwater droplets in suspension (Ground Level Cloud) Occurs when Temp & Dew Point are within 5° and wind is low


Moisture and CloudsMoisture and Clouds Clouds

Like Fog, Clouds are a mass of water droplets in suspension, but they can also contain ice crystals, or water / ice mixed

There are 3 basic Cloud Forms: CumulusCumulus - White, Billowy, Puffy (Cotton Balls), Low Level

– Normally seen in good weather, but also associated with turbulence

StratusStratus - Thin, Sheet like, Grey, Low Level CirrusCirrus - White, Thin, Wispy, High Level

Precipitation When the temperature fall too far below the Dew Point, and the

Cloud can no-longer hold the moisture in suspension, Precipitation Results Either Rain, Snow or IceRain, Snow or Ice (hail) depending on temperature Precipitation is measured with a Rain GaugeRain Gauge Precipitation reduces Visibility, and makes runways slippery Ice increases Aircraft weight, and can block inlets


Weather Systems and ChangesWeather Systems and Changes

Air MassesAir Masses - A HUGE mass of air Normally at least 1000 miles across Essentially the same Temperature and Moisture

characteristics throughout Air masses are classified by where they came from, i.e. their

Source Region The 6 Source Regions are:

cA - continental Arctic cP - continental Polar cT - continental Tropical mT - maritime Tropical mP - maritime Polar mE - maritime Equatorial

Maritime masses are wetter Farther away from the equator = a colder mass



FrontsFronts - the boundary between 2 air masses: WARMWARM Fronts ride up over Cold Air Normally COLDCOLD Fronts are heavy and low,

and push Warm Fronts up, and away When similar air masses meet, there may not be

enough difference to cause movement, and a SSTTAATTIIOONNAARRYY Front occurs

An OCCOCCLULUDEDDED Front (3 air masses) the Warm air is still pushed up, but relatively cool air is pushed up also by colder air ColdCold OcclOccludeduded - Old Cool Air pushed up,

basically like a Cold Air snowplough, pushing everything Upwards

WarmWarm OcclOccludeduded - New Cool Air pushed up behind Warm Air, by local colder air


Weather Systems and ChangesWeather Systems and Changes Severe Weather

CumulonimbusCumulonimbus clouds are a sign of Severe Weather, which could be a Thunderstorm, Tornado or Hurricane

ThunderstormsThunderstorms Heavy Winds, Strong Rain, Sometimes Hail Lightning - Electric Discharge, which can heat the air to 60,000°F!

– About 200 are killed and 600 injured by lightning in the US annually!– 3 stages: Building (Updrafts), Mature (Up/Down air cycles),

Dissipating (Downdrafts)

Do’s and Don’ts:– Don’t use electric appliances, telephones, or take a shower– DO Stay away from Windows and Doors– If Outdoors, DO go Inside– If in a car, DO stay there– If in a boat, DO get ashore– DO Move away from Water and Metal objects– Don’t stand in open space, or under a tree– DO Stay Low, and Don’t huddle in a group



TornadoesTornadoes Fujita Wind Damage ScaleFujita Wind Damage Scale - F0 to F5F0 to F5, with wind speed range and

expected scale of damage for each– F5 is over 261 MPH, with ‘Incredible’ Damage resulting

– Do’s and Don’ts:» DO Get to a Basement (or lie down in low ground)» DO, If above ground, move at 90° to the Tornado» DO, if indoors, stay away from windows, got to the interior, or into

a closet or bathroom

HurricanesHurricanes Saffir-Simpson Hurricane Damage Potential ScaleSaffir-Simpson Hurricane Damage Potential Scale -

Cat 1 Cat 1 (75-95 MPH)(75-95 MPH), to Cat 5 to Cat 5 (155+ MPH!)(155+ MPH!), with Pressure Range, Wind Speeds, and Storm Surge (Sea Level

increase)– Do’s and Don’ts:– same as Thunderstorms & Tornadoes, since they can produce BOTH– Worse, they can be HUGE, and can continue for more than a week!– But, Hurricanes have a ‘Eye’ at the center which is calm

Documents

Dr. R.A. Bartholomew - Civil Air Patrol, New Jersey Wing1 Cadet Phase I & II Aerospace Dimensions Air Environment (Module 3) Session 1: Chapter 1 ‘Air