Gasses of the Atmosphere



What is an atmosphere?

Ask for student input

Describe in general terms


Gasses of the Atmosphere

What is the atmosphere?

Collection of gasses

Matter, so has mass, gravitational attraction, etc.

Source? Volcanic and/or cosmic

Current composition - see fig. 9-1, page 228

Gasses, solids, and liquids

Stratification of the atmosphere - See fig. 9-3, page 230

Primarily based on composition, density, and temperature differences

See fig. 9-5, page 232

Has evolved through time

Carbon dioxide out, nitrogen & oxygen in

Banded iron formation

Air Pressure (start with a discussion of water pressure - easier to understand)

Weight of the matter at the surface

Decreases upward as atmosphere thins

14.7 lbs/in^2 at the surface

DEMO: meter stick and paper


Atmospheric energy budget (solar energy)

All energy comes from the sun

Solar energy reflected or absorbed - see fig. 9-9, page 239

Energy transmitted in 3 ways - see fig. 9-11, page 241

Radiation - direct electromagnetic waves from the source

The sun, heat register in a room, etc.

Conduction - direct contact with a heat source

Electric stove, hot sand

Convection - transfer of heat energy due to density differences

Causes currents from areas of high density to low density

Differential heating of surface by the sun

Equator vs. the polar regions

Review langleys

Results in high vs. low pressure areas

High pressure

Cold air, molecules closer together, increased density

Low pressure

Warm air, molecules farther apart, decreased density

DEMO: metal can with small amount of water

Heat, drive out air, seal, cool, can will collapse

What happened?

Global wind patterns

Air currents always move from high to low pressure

Attempt to restore equilibrium

In a perfect world...

Refer to "Weather" by Life Science Library, page 69

All winds would blow from south to north, or the reverse

Due to convection - describe energy and flow patterns

Heating at equator

Air becomes less dense

Rises to higher elevation

Sets up convection cells

But it's not a perfect world

Refer to "Planet Earth: Atmosphere" Time/Life page 84/85

Spinning on its axis

Causes the Coriolis Effect - Describe

Changes wind patterns


Air is just air! It's the water!

Check out GeoMan's section on weather and climate