1. Structure of the Earth’s Atmosphere * Chemical Composition * Vertical Layers * Coriolis Force * Hadley Cells

2. Current Composition

3. Atmospheric Composition today

5. Troposphere  Surface layer - 30,000 ft  Heated from below  General T structure dec. w/height  Convection - weather, clouds form from rising air which cools by pressure drop, and clouds dissipate as air falls and heats.

6. Stratosphere  Heated by ozone absorbing UV light  UV breaks apart ozone into O 2 + atomic oxygen - get energy release and heating.  higher altitudes efficiently absorbs UV at 200 and 350 nm.  lower altitudes less efficiently absorbs UV at 44 and 80 nm  Temperature inversion - no convection, no weather.  7 – 30 miles

7. Mesosphere  Mass of atmosphere 0.1%  Density is too low for ozone chemistry to heat  get normal trend we saw in troposphere– lower T with inc. altitude.  30-50 miles

8. Ionosphere (= Thermosphere)  Density so low Space Shuttle orbits here, with little drag  T can be very high; 4,000F.  But no significant heat because density low.  Heated by ionization by UV from the sun, and the solar wind.

9. Hadley Cells

10. Hadley, Ferrel, Polar Cells  Earth’s atmosphere divides into 3 cells.  Coriolis deflection sets the major constraint on how many cells the atmosphere of a planet divides into.  stronger for more rapid rotation.  size of the planet and speed of rotation  which determines number of cells

11. Hadley Cell  Solar heating at equator is strongest - causing rising convective air which is pushed north and south at the tropopause  At ~30deg latitude deflected enough by Coriolis force to be moving almost due east.  Meets air moving down from the north (Ferrel Cell air) and both descend, warming and drying  Trade Winds - return of surface wind to equator

12. Coriolis Effect  6 min YouTube (start 1min in for merry-go-round demo) 6 min YouTube