1. The Earth's Atmosphere

2. The atmosphere is the layer of air that surrounds the Earth
- It protects us from harmful solar radiation (ex., UV radiation)
- It provides living things with the gases they need to live (CO2 for plants, O2 for animals)
- It maintains a temperature range on the planet that allows life to exist (without it the earth would be -18ºC)

4. How thick is the atmosphere?
Gravity pulls the gases toward the earth
While 99% of the gases in the atmosphere are in the first 30 km above the surface of the earth, the atmosphere is considered to extend more than km.

6. The Composition of the Atmosphere
Almost all composed of two gases,
Nitrogen (N2) = 78%
Oxygen (O2) = 21%
Also..
Water vapor = 0-4%
Argon = .93%
CO2 = .038%
Ozone = %
And more...

8. Atmospheric pressure Because of gravity, most of
The molecules of air are
close to the earth (99%
within 30 km). This means
the density and pressure
of the atmosphere is
greater at lower altitudes.
The pressure at the surface
Is 14.7 pounds per square inch.
(On Mt. Everest the pressure is about 4.5 pounds psi.)

10. The Layers of the Atmosphere

11. Troposphere From the surface to 10 - 15 km
Most clouds and storms occur in this layer
The temperature drops with altitude

12. Stratosphere
15 – 50 km
This layer contains the ozone layer (O3), which absorbs UV radiation, this makes it warmer

13. Mesosphere
50 – 80 km
Very cold (-80⁰C), very few air particles

14. Thermosphere 80 – 500 km Hottest layer of the
atmosphere (up to 2000⁰C),
it absorbs most of the sun’s
radiation. Because of the
rarity of air particles it
doesn’t feel hot.

15. The Exosphere 500 - 10 000 km Basically empty, outer space
Satellites orbit earth
in this layer.

16. Atmospheric Circulation
Driven by the rotation of the earth and convection.
Convection – warm air at the equator rises and travels to the poles. Cold air moves south closer to the surface

17. The combination of convection and the Earth’s rotation makes the air circulation complex
The Coriolis effect is the result
Air moves in curved paths

18. Explaining and predicting the weather
The movement of air in the atmosphere has certain trends that we can identify.
It’s important to be aware that there is a fair amount of ‘randomness’ or unpredictability in the weather. This is the ‘Butterfly Effect’.

19. Circulation Cells (acc)
Air circulates
in loops called
cells. The cells
are called
Hadley, Ferrel,
And Polar cells.

20. The convection currents are divided into cells, but the basic principle of rising warm air and sinking cold air drives the circulation. Prevailing winds are created that move in predictable directions based on the Coriolis effect

21. To refer to areas on the Earth’s surface, we divide the planet into vertical and horizontal slices called longitude and latitude.
Latitude,
from 0⁰ to 90⁰ North and South
Longitude,
from 0⁰ to 180⁰ East and West

22. Trade winds are easterly(they come from the east) , from the equator to the 30th parallel. Westerlies blow from the west between the 30th and 60th parallel. Polar easterlies blow from the east between the 60th and 90th parallel.

23. At high altitudes the Jet Streams blow from the west between the cells
The Polar is at the 60th parallel, 10 km, <300 km/h
The Subtropical th parallel, 12 km, <400 km/h

24. Air Masses
Large volumes of air that are uniform temperature and humidity are called air masses.
Quebec receives warm, moist air masses from the South and cold, dry air masses from the North.
When two air masses meet, a Front is created.
Depending on which air mass is moving, the result can be a cold front or a warm front.

25. Cold Front A cold air mass pushes the warm air mass up.
The warm, moist air
condenses. Thunderstorms
Are created along the front.
Cold fronts are represented with
blue lines with arrows.

26. Warm Front A warm air mass slowly slides over
a cold front. Precipitation
is spread over a broad area
at different altitudes.
Represented with a red line
with semicircles.

27. Anticyclones and Depressions
The vertical rise and fall of air (as opposed to the horizontal movement of air masses) can cause depressions and anti-cyclones.
When warm, moist air rises a depression is created. ‘Depression’ refers to the lower air pressure left behind when the warm air rises.
Cold air dropping toward the surface creates a high pressure area. This is called an anti-cyclone.

28. Depressions can become Hurricanes (aka typhoon, cyclone)

29. Hurricane Isabella - 2003 – Atlantic Ocean - tropics

30. Rising warm air creates a low pressure zone.
A convection current around the rising air forms.
The earth’s rotation creates the spin (Coriolis effect)
Wind speed at the
can be over 350 km/h.
The size of a hurricane
can be over 1500 km in
diameter.

31. Anti-cyclone (high pressure zone)
This occurs when relatively cold air drops vertically, creating higher air pressure.
Skies are
sunny and clear.

32. The Greenhouse Effect
Reflected heat radiation off the surface of the Earth heats up gases, which then retransmit the heat, partly back to Earth. Water vapour, CO2, CH4 (methane) and ozone have the greatest contribution to the greenhouse effect, though almost all gases in the atmosphere play a part

34. The greenhouse effect is what makes the Earth’s climate liveable. But…
As more greenhouse gases are released, the concern is that the average temperature will rise too much. Glaciers will melt, etc.
CO2 – burning of fossil fuels, clear-cutting forest
CH4 – methane produced by cattle and decomposing waste
N2O – released from nitrogen rich fertilizers
CFC’s – chlorofluorocarbons destroy ozone

36. It is estimated that the Earth’s average temperature has risen by 0
It is estimated that the Earth’s average temperature has risen by 0.76⁰C in the last 150 years.
It is predicted that a rise of 2⁰C would cause widespread environmental consequences.

37. The Thinning Ozone Layer (acc)
In addition to influencing global warming, the ozone layer blocks much of the UV radiation from the sun. This radiation can cause harm to living things through cell damage and genetic damage.
For years, CFC’s were used in aerosols and refrigerators. These gases destroy ozone by releasing chlorine that reacts with it.

39. In 1987, an agreement was reached to stop the production of CFC’s.
The hope is that the ozone layer will recover in the next century.

40. Smog

41. Smog (acc) Ozone can be harmful to life if it close to the surface.
Pollution from human industry and vehicles (nitrogen oxides) reacts with the sun’s rays to form ozone.
Mixed with smoke and fog, it is called smog.
Smog can cause respiratory (breathing) illnesses.

42. Energy from the air
Wind is a plentiful renewable resource, and we are taking advantage of this more and more by building very large wind turbines.
Turbines can be 100 m tall and produce 2 MW of electrical power, enough to supply homes (based on average household power consumption of 1 kW.)

43. - Designs are improving
- Designs are improving. - Turbines are getting bigger and more powerful. - But the wind isn’t constant. - A combination of energy types will be needed.

44. That’s it for the atmosphere (take a deep breath).
11/10/2017