What is an atmosphere?
Ask for student input
Describe in general terms
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
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
Check out GeoMan's section on weather and climate