1. Basic Properties of the Atmosphere

3. Composition of the Atmosphere
Nitrogen (78.08% ~ 78%)
Oxygen (20.95% ~ 21%)
Argon 0.93% (9300 parts per million)
Carbon Dioxide % (350 ppm)
Neon 18 ppm
Helium 5.2 ppm
Methane 1.4 ppm
Ozone ppm

4. Other Components of the Atmosphere
Water Droplets
Ice Crystals
Sulfuric Acid Aerosols
Volcanic Ash
Windblown Dust
Sea Salt
Human Pollutants

5. Structure of the Atmosphere
The atmosphere is thicker at the equator, thinner at the poles
4 Levels Defined by Temperature
a. Troposphere (cools farther from surface)
Where Weather (moisture) Happens
b. Stratosphere
Ozone Layer (O3), blocks ultraviolet radiation
c. Mesosphere- gets way cold
d. Thermosphere- hot due to large amount of solar radiation, but you freeze b/c low # of molecules!
Includes the Ionosphere (Northern Lights)

7. Troposphere (0 – 15km) Temperature of 20C at surface to -60C at 15km
Convection Currents: Heating rock and water at the Surface creates warm air at surface, Warm air rises, but air expands as it rises and cools as it expands, then it sinks again
Two opposing action = constant turnover, keeps our atmosphere mixed.

9. Stratosphere Altitude 15-50 km Temperature increases with altitude
-60 C at base to 0 C at top
Reason: absorption of solar (ultraviolet) energy to make ozone at upper levels (ozone layer)
Ozone (O3) is effective at absorbing solar ultraviolet radiation

11. Mesosphere 50 – 80 km altitude Temperature decreases with altitude
0 C at base, -95 C at top
Top is coldest region of atmosphere

13. Thermosphere 80 km and above
Temperature increases with altitude as atoms accelerated by solar radiation
-95 C at 80km to +100 C at 120 km
Cannot feel the heat.
Traces of atmosphere to 1000 km
Formerly called Ionosphere

14. Why is the Mesosphere so Cold?
Stratosphere warmed because of ozone layer
Thermosphere warmed by atoms being accelerated by sunlight
Mesosphere is sandwiched between two warmer layers, nothing warms it up.

15. Composition and Altitude
Up to about 80 km, atmospheric composition is uniform (troposphere, stratosphere, mesosphere)
Above 80 km light atoms like hydrogen and helium rise above the other heavier molecules of nitrogen and oxygen..

16. What happens above 120 km
Below 80 km, an atom accelerated by solar radiation will very soon hit another atom
Energy gets evenly distributed in the atmosphere
Above 80 km atoms rarely hit other atoms
Light atoms get accelerated and have more movement and fly higher, but few atoms escape entirely

17. Atmospheric Layers

18. Energy Balance Reflected = 25 + 5 = 30 Absorbed = 25 + 45 = 70
From Cunningham & Cunningham, 2004, Fig. 9.2