1. 13.4 Atmosphere read pp
The blanket of air and moisture that surrounds the Earth
density of the atmosphere decreases with elevation
air of lower atmosphere is dense due to the weight of overlying air

2. Exosphere
Thermosphere
Mesosphere
Stratosphere
Troposphere

3. Atmospheric Composition
Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon Dioxide 0.03%
traces of other gases

5. Atmospheric Composition
Water vapour : considered a variable gas, can make up 4% of the volume of the air
solids are also present: smoke, dust, volcanic ash, soil etc.

6. Troposphere 8-16 km altitude thicker at equator
most of atmospheric moisture and weather
temp decreases with altitude
tropopause

7. Stratosphere highest [O3]
temp rises above tropopause because ozone absorbs UV
~12-50 km
very dry

8. Mesosphere km
temperature and density extremely low

9. Thermosphere Exosphere: space? or ionosphere
density still low but very energetic molecules thus high temperatures
auroras
Exosphere: space?

10. structure of atmosphere video

12. Atmospheric Pressure:
Force which air exerts as a result of gravity

13. Pressure Gradient:
amount atmospheric pressure changes across a set distance
fig 4a and 4b p.512

14. Isobars are lines of equal pressure
when isobars are close together the gradient is higher, usually indicating strong winds
check weather maps

16. Drawing Isobars video

20. Temperature Gradient:
change in temperature over a distance
in the troposphere this gradient is -6°C per 1000 m,
i.e. the temperature drops 6°C for every 1000 m of elevation

21. Supporting Life the atmosphere is necessary to life…
O2 is necessary for breathing
N is essential for plant growth
CO2 is used by plants
O3 filters out UV

22. Supporting Life con’t plays a role in the water cycle
absorbs meteroids
regulates temperatures

24. Atmospheric Pressure measured in kilopascals 1 kPa = 1000 Pa
fig 5, p 512 aneroid barometer

25. Low pressure areas have less atmospheric mass above their location, high pressure areas have more atmospheric mass above their location.
Similarly, as elevation increases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation.

26. Weather Balloons
Radiosonde: instrument with electronic sensors which transmit temperature, air pressure, water vapour to ground stations
radar tracking gives wind speed and direction

28. UC questions p 513 2, 3, 6