Transcript AtmStructure

Structure of the
Earth’s Atmosphere
* Chemical
Composition
* Vertical Layers
* Coriolis Force
* Hadley Cells
Current Composition
Atmospheric Composition today
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.
Stratosphere
 Heated

by ozone absorbing UV light
UV breaks apart ozone into O2 + 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
7
– 30 miles
inversion - no convection, no weather.
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
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.
Hadley Cells
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
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
Coriolis Effect
6
min YouTube (start 1min in for merry-go-round
demo)