Chapter 3
Earth’s Modern
Atmosphere
Robert W. Christopherson
Charlie Thomsen
Earth’s Modern Atmosphere
Atmospheric Composition, Temperature,
and Function
Variable Atmospheric Components
Atmospheric Composition,
Temperature, and Function
Atmospheric Profile
Atmospheric Composition Criterion
Atmospheric Temperature Criterion
Atmospheric Function Criterion
Atmospheric Profile
Atmosphere extends to 32,000 km
(20,000 mi) from surface
Thermosphere is at 480 km (300 mi)—top
of the principal atmosphere
Three criteria to examine atmosphere
Composition
Temperature
Function
Profile of
Atmosphere
Figure 3.2
Atmospheric
Pressure
Figure 3.3
Atmospheric Composition
Heterosphere – outer atmosphere
80 km (50 mi) outward, to thermosphere
Layers of gases sorted by gravity
Homosphere – inner atmosphere
Surface to 80 km (50 mi)
Gases evenly blended
CO2 increase
1958–2007
Figure 3.4
Atmospheric Temperature
Thermosphere
Roughly same as heterosphere
80 km (50 mi) outward
Mesosphere
50 to 80 km (30 to 50 mi)
Stratosphere
18 to 50 km (11 to 31 mi)
Atmospheric Temperature
Troposphere
Surface to 18 km (11 mi)
90% mass of atmosphere
Normal lapse rate – average cooling at rate of
6.4 C°/km (3.5 F°/1000 ft)
Environmental lapse rate – actual local lapse
rate
Temperature
Profile
Figure 3.6
Atmospheric Function
Ionosphere
Absorbs cosmic rays, gamma rays, X-rays,
some UV rays
Ozonosphere
Part of stratosphere
Ozone (O3) absorbs UV energy and converts it
to heat energy
Protective
Atmosphere
Figure 3.7
Antarctic
Ozone
Hole
2006
Figure FS 3.1.1
ClO
and
O3
Figure FS 3.1.2
Variable Atmospheric Components
Natural Sources
Natural Factors That Affect Air Pollution
Anthropogenic Pollution
Benefits of the Clean Air Act
Natural Factors That Affect
Air Pollution
Winds
Local and regional landscapes
Temperature inversion
Southern California Wildfires
Figure 3.8
Temperature Inversion
Figure 3.10
Anthropogenic Pollution
Carbon monoxide
Photochemical smog
Industrial smog and sulfur oxides
Particulates
Forests on Fire
Figure 3.12
Air Pollution
Figure 3.14
Photochemical Smog
Figure 3.15
Benefits of the Clean Air Act
Total direct cost $523 billion
Direct monetized benefits $5.6 to $49.4
trillion – average $22.2 trillion
Net financial benefit $21.7 trillion
206,000 fewer deaths in 1990!
End of Chapter 3
Geosystems 7e
An Introduction to Physical Geography
Robert W. Christopherson
Charlie Thomsen