1. 5.01 Heating and Cooling of the Atmosphere
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

2. Ground School 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

3. Ground School 5.01 Vertical Structure
Troposphere
Weather happens here
To 25,000 – 30,000 feet over poles
To 55,000 – 65,000 feet over equator
Temperature decreases with height
Stratosphere
Troposphere to 170,000’
Temperature increases with height

4. Ground School 5.01 Vertical Structure
Mesosphere
Stratosphere to 270,000’
Temperature decreases with height, to -85°C
Thermosphere
Tops at 1.1 million to 2.6 million feet ( kilometres)
Temperature increases with height, up to 1,500°C
Exosphere
Mainly comprised of hydrogen and helium
Extends into space

5. Ground School 5.01 Vertical Structure
Label the layers of the atmosphere!
Choose from these:
Stratosphere
Thermosphere
Exosphere
Troposphere
Mesosphere

6. Ground School 5.01 Composition
The atmosphere is made up of what main gases?
Answer:
Nitrogen
Oxygen
Other (Argon, CO2,
water vapour, etc)
*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.

7. Ground School 5.01 ICAO Standard Atmosphere
The International Civil Aviation Organization (ICAO) Standard Atmosphere:
Sea Level for North America
Based on summer and winter averages at 40°N latitude
The Standard:
MSL pressure of 29.92” Hg ( hpa)
MSL temperature of 15°C
Air is a “perfectly dry gas”
Lapse rate of 1.98°C per 1000 feet

8. Ground School 5.01 Temperature Scales
Sun heats earth, earth heats atmosphere
Celsius (nearly worldwide):
Freezing point: 0°C
Boiling point: 100°C
Fahrenheit (USA):
Freezing point: 32°F
Boiling point: 212°F
Conversion  °C x (9/5) + 32 = °F
****Does anybody know of a third temperature scale???
--Kelvin °K = 0°C

9. Ground School 5.01 Properties of the Atmosphere
Mobility
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
Air is compressed as it descends into greater pressure
Occupies less space

10. Ground School 5.01 Properties of the Atmosphere
Expansion
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!

11. Ground School 5.01 Atmospheric Density
Density - mass per unit volume
Cold air is dense:
Molecules are move slowly and are packed close together
Heavier and tends to sink
Warm is less dense:
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

12. Ground School 5.01 Atmospheric Density
Density Relationships:
Density vs. Temperature:
Indirectly proportional
As temperature increases, density decreases
Density vs. Humidity:
As water vapour increases, density of the air decreases
Density vs. Pressure:
Directly proportional
As pressure decreases, density decreases

13. Ground School 5.01 Temperature Differences
Horizontal Temperature Differences
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

14. Ground School 5.01 Temperature Differences
Horizontal Temperature Differences:
Topography
Land and water differences
Clouds
Clouds reflect large amounts of solar radiation
At night, clouds trap the heat radiated off the earth
i.e. earth cools more rapidly on a clear night vs. cloudy night

15. Ground School 5.01 Temperature Differences
Types of Atmospheric Heating:
Radiation (heating)
Earth absorbs sun’s
short wave radiation
The lower atmosphere
is then heated by the earth

16. Ground School 5.01 Temperature Differences
Conduction
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

17. Ground School 5.01 Temperature Differences
Convection
Air heated through conduction becomes buoyant and rises
This air then heats the air in the upper atmosphere

18. Ground School 5.01 Temperature Differences
Advection (heating)
Occurs when cold air moves over a warm surface and its lower layer is heated by conduction

19. Ground School 5.01 Temperature Differences
Turbulent Mixing
Turbulent air mixes a warmer surface layer of air with an unheated air aloft, spreading the heat upward

20. Ground School 5.01 Temperature Differences
Compression
As air descends it compresses due to increased pressure and therefore heats up

21. Ground School 5.01 Temperature Differences
Types of Atmospheric Cooling:
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

22. Ground School 5.01 Temperature Differences
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

23. Ground School 5.01 Temperature Differences
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

24. Ground School 5.01 Temperature Differences
End