Ground School: Meteorology
5.01 Heating and Cooling of
the Atmosphere
References:
-Transport Canada Study and Reference Guide Pilot
- FTGU pages 123,124, 136 and 137
Instructor
40 Minutes
Ground School
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5.01 Heating and Cooling of the Atmosphere
MTPs:
 Vertical
Structure
 Composition
 ICAO Standard Atmosphere
 Temperature Scales
 Atmospheric Properties
 Atmospheric Density
 Temperature Differences, Heating and Cooling
Ground School
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Troposphere
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Weather happens here
To 25,000 – 30,000 feet
over poles
To 55,000 – 65,000 feet
over equator
Temperature decreases
with height
Stratosphere
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Troposphere to 170,000’
Temperature increases
with height
5.01 Vertical Structure
Ground School
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Mesosphere
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Thermosphere
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Stratosphere to 270,000’
Temperature decreases
with height, to -85°C
Tops at 1.1 million to 2.6
million feet (350-800
kilometres)
Temperature increases
with height, up to 1,500°C
Exosphere
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
Mainly comprised of
hydrogen and helium
Extends into space
5.01 Vertical Structure
Ground School

Label the layers of the
atmosphere!
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Choose from these:

Stratosphere
Thermosphere
Exosphere
Troposphere
Mesosphere
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5.01 Vertical Structure
Ground School
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5.01 Composition
The atmosphere is made up of what main gases?
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Answer:
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Nitrogen
Oxygen
Other (Argon, CO2,
water vapour, etc)
Nitrogen
Oxygen
Other
*Although water vapour is less than 1% of the atmosphere, it remains
the most important component from the standpoint of weather,
based especially on its ability to change state.
Ground School
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The International Civil Aviation Organization (ICAO)
Standard Atmosphere:
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5.01 ICAO Standard Atmosphere
Sea Level for North America
Based on summer and winter averages at 40°N latitude
The Standard:
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MSL pressure of 29.92” Hg (1013.25 hpa)
MSL temperature of 15°C
Air is a “perfectly dry gas”
Lapse rate of 1.98°C per 1000 feet
Ground School
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Sun heats earth, earth heats atmosphere
Celsius (nearly worldwide):
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Freezing point: 0°C
Boiling point: 100°C
Fahrenheit (USA):
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5.01 Temperature Scales
Freezing point: 32°F
Boiling point: 212°F
Conversion  °C x (9/5) + 32 = °F
Ground School
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Mobility
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5.01 Properties of the Atmosphere
The ability for air to move
Atmosphere like an “ocean of air”
Wind like “streams of water”
(Much more freedom of movement with air than water)
Compression

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Air is compressed as it descends into greater pressure
Occupies less space
Ground School
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5.01 Properties of the Atmosphere
Expansion
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As air rises, it reaches areas of lower pressure, causing
it expand and cool
This cooling can be enough to condense water vapour
in the air, forming cloud
This is why clouds and precipitation are common in
areas of rising air
From a meteorological standpoint, the most important
property of the air!
Ground School
5.01 Atmospheric Density
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Density - mass per unit volume
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Cold air is dense:
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Molecules are move slowly and are packed close
together
Heavier and tends to sink
Warm is less dense:
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Molecules are moving rapidly taking up more space (or
less molecules in the same space)
Warm air is lighter and is pushed up by the cold air
Ground School
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5.01 Atmospheric Density
Density Relationships:
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Density vs. Temperature:
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Density vs. Humidity:
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Indirectly proportional
As temperature increases, density decreases
Indirectly proportional
As water vapour increases, density of the air decreases
Density vs. Pressure:
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Directly proportional
As pressure decreases, density decreases
Ground School
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5.01 Temperature Differences
Horizontal Temperature Differences
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Diurnal Variation
 Atmosphere warms during day, cools at night
Seasonal Variation
 Amount of solar radiation changes seasonally due to
Earth’s tilt
Latitude
 Sun is more directly overhead near equator
Ground School
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5.01 Temperature Differences
Horizontal Temperature Differences:
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Topography
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Land and water differences
Clouds
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Clouds reflect large amounts of solar radiation
At night, clouds trap the heat radiated off the earth
Ground School
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Types of Atmospheric
Heating:
Radiation (heating)
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Earth absorbs sun’s
short wave radiation
The lower atmosphere
is then heated by the
earth
5.01 Temperature Differences
LONG & SHORT WAVE’S
SHORT WAVE
INSOLATION
LONG WAVE
TERRESTRIAL
RADIATION
6
Ground School
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5.01 Temperature Differences
Conduction
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If two substances are in
contact, heat will flow from
the warmer to the colder
substance
ie. Layers of air of different
temperatures being in contact
Air is a poor conductor, so this
usually only occurs in small
layers
 Unless heat is distributed
through vertical motion
Cold air
Solar radiation
Cool air
Air warmed by conduction
warm surface
Ground School
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5.01 Temperature Differences
Convection
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Air heated through
conduction becomes
buoyant and rises
This air then heats the air
in the upper atmosphere
Convection
COLD AIR
mixing
occurs
COLD AIR
warm
air
rises
COLD AIR
heat is carried
vertically
by convection
WARM SURFACE
9
Ground School
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5.01 Temperature Differences
Advection (heating)

Occurs when cold air
moves over a warm
surface and its lower
layer is heated by
conduction
Advection
COLD
advective warming
WARM SURFACE
WARM
Ground School
5.01 Temperature Differences
TURBULENT MIXING

Turbulent Mixing
 Turbulent air mixes a
warmer surface layer of
air with an unheated air
aloft, spreading the
heat upward
 WIND CAUSES
TURBULENCE
 MIXES LOW
LEVEL HEAT TO
UPPER LEVELS
Cool air
Turbulent
mixing
warm air
warm surface
11
Ground School
5.01 Temperature Differences
Compression
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Compression
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As air descends it
compresses due to
increased pressure and
therefore heats up
Sinking Air is
compressed by
higher pressure
and its temperature
will increase
Ground School
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5.01 Temperature Differences
Types of Atmospheric Cooling:
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Radiation cooling
 Occurs at night
 Surface layer of air touching
earth cools as earth cools
 Most commonly only affects
first 4000 feet of the
atmosphere
Radiation Cooling
Warmer Air
Terrestrial Radiation
Warm Air
Air cooled by conduction
Cool Surface
Ground School
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Advection cooling
 Lower levels only
 When air is cooled by
moving over a colder
surface
 Cooling occurs as a result of
conduction between air and
surface
 Some mechanical
turbulence can aid in
spreading cooling effect
5.01 Temperature Differences
Advection Cooling
WARM
Warm Air moving
Over a cooler surface
advective cooling
COLD
cool surface
Ground School
5.01 Temperature Differences
Expansion Cooling

Expansion cooling
 The most important
cooling process of the
air
 Air forced to rise
experiences lower
pressure and is allowed
to expand
 This expansion causes
decrease in temperature
Lower pressure
AIR
EXPANDS
&
COOLS
WARM
COOL
Lower pressure
Ground School
5.01 Temperature Differences
End