1. The Atmosphere

2. The atmosphere The atmosphere
Acts as a screen against harmful radiation
Retains heat allowing for life on Earth
Includes O2 necessary for cellular respiration and CO2 necessary for photosynthesis
Our atmosphere covers our planet because of the gravitational field of our planet

3. Composition of the air
Atmosphere: layer of gas (especially nitrogen and oxygen) that surrounds our planet
Air is made up of:
78% Nitrogen (N)
21% Oxygen (O2)
1% of other gases
Water Vapor
CO2
Argon …

4. Atmospheric layers Troposphere: (0-15km) Stratosphere: (15-50 km)
Where meteorological phenomenon occur
Stratosphere: (15-50 km)
Ozone layer
Temperature increases due to ozone layer
Mesosphere: (50-80 km)
Coldest layer of the atmosphere (-80C)
Thermosphere: ( km)
Hottest layer of the atmosphere (1800C)
Exosphere: (500 km and up)
Where satellites are placed

5. Atmospheric pressure Air is a fluid Atmospheric pressure
Is the weight per unit area (pressure) of the column of air above that location.
the pressure of the air in the atmosphere
Varies with time and place
To measure pressure we use a barometer
Units of measurement = Pascals
Average air pressure at sea level = Pa

6. Factors affecting atmospheric pressure
If the number of air particles
Increase : then pressure increases
Decrease: then pressure decreases
There is a natural thinning of our atmosphere with altitude and therefore a natural decrease in pressure
If temperature of the air
Increase: (the molecules are flying every which way) the pressure will decrease
Decreases: the pressure will increase
**Warm air is therefore less dense than cold air

7. Another interesting factor
Water vapor
If the amount of water vapor increases: the air pressure will actually decrease, because humid air is actually less heavy than dry air.

8. What does all this mean?
Because density changes with the temperature, the atmosphere will undergo “atmospheric circulation”
Atmospheric circulation is the global-scale movement of the layer of air surrounding the Earth
Which really comes down to… atmospheric circulation is the global-scale movement of the atmosphere

9. Atmospheric Circulation

12. Coriolis Effect Definition:
Winds deviate to the right in the Northern Hemisphere
Winds deviate to the left in the Southern Hemisphere

14. 2. 3. 1.

15. Circulation cells Hadley Cells Ferrel cells Polar Cells
Between the equator and 30th latitude
Warm air rise at equator
Creates the trade wind
Ferrel cells
Between the 30th latitude and 60th latitude
Creates the westerlies (from west to east)
Polar Cells
Between the 60th latitude and the poles
Creates the polar easterlies (from east to west)

16. Prevailing winds Definition: Between
Major atmospheric current that blow in a given direction according to global patterns of movement near the surface.
Between
Equator and 30th parallel
Tropical easterlies or trade winds
30th parallel and 60th parallel
Westerlies
60th parallel and pole
Polar easterlies

17. Other winds Regionally, Jet streams
winds do not always blow in the same direction as the prevailing winds. They are affected by local high pressure and low pressure system
Jet streams
Subtropical Jet stream
Around the 30th parallel
Travels at 400 km/h 11 km above the surface
Polar jet stream
Around the 60th parallel
Travels at 300 km/h

18. Air Masses, anticyclones and cyclones
Weather Makers
Air Masses, anticyclones and cyclones

19. 1. Air masses Definition:
Large expanse of the atmosphere with relatively uniform temperature and humidity.
Air mass characteristics:
Humidity (humid or dry)
Temperature (cold or warm)

20. 1. Air masses
When air masses collide they create fronts. They do not mix.
a) Cold Front
b) Warm Front
c) Stationary
d) Occluded

21. a) Cold front Occurs when… Symbol Weather
A cold air mass overides a warm air mass
Symbol
Weather
The warm air rises abruptly, causing the water vapor to rise and condense and produces storm clouds

22. a) Cold Front

23. b) Warm front Occurs when… Symbol Weather
A warm air mass overrides a cold air mass
Symbol
Weather
The warm air rises slowly, causing the water vapor to rise and condense and produces clouds

24. b) Warm Front

25. c) Stationary Front Occurs when… Symbol Weather
A warm air mass meets head on a cold air mass
Symbol
Weather
The masses collide, the warm air rises over the cold denser air, causing the water vapor to rise and condense and produces clouds and rain on the cold front

26. d) Occluded Fronts Occurs when… Symbol Weather
A cold front catches up with a warm front
Symbol
Weather
The cold front catches up with the warm front and forces it from the ground

27. d) Occluded Front

28. 2. Cyclones and anticyclones
A cyclone:
Area of low atmospheric pressure. The air turns counterclockwise in the Northern hemisphere and clockwise in the Southern Hemispheres.
An anticyclone:
Area of high atmospheric pressure. The air turns clockwise in the Northern hemisphere and counterclockwise in the Southern Hemispheres.

29. Hurricanes:
A large cyclone characterized by violent winds

30. Atmospheric issues Smog Ozone layer thinning Contaminants
Thick layer of fog and smoke and atmospheric pollutants
Ozone layer thinning
Contaminants
Acid Rain, smog, toxic chemicals, dust and ozone destruction
Greenhouse gases
Climate change: abnormal modification of climatic conditions on Earth, caused by human activity

31. Energy resources
Solar energy
Wind energy