1. Chapter 3 Earth’s Modern Atmosphere
Robert W. Christopherson
Charlie Thomsen

3. Earth’s Modern Atmosphere
Atmospheric Composition, Temperature, and Function  
Variable Atmospheric Components  

4. Atmospheric Composition, Temperature, and Function
Atmospheric Profile  
Atmospheric Composition Criterion  
Atmospheric Temperature Criterion  
Atmospheric Function Criterion  

5. 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

6. Profile of Atmosphere
Figure 3.2

7. Atmospheric Pressure
Figure 3.3

8. 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

10. CO2 increase
1958–2007
Figure 3.4

11. 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)

12. 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

13. Temperature Profile
Figure 3.6

14. Atmospheric Function Ionosphere Ozonosphere
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

15. Protective Atmosphere
Figure 3.7

16. Antarctic Ozone Hole 2006
Figure FS 3.1.1

17. ClO and O3
Figure FS 3.1.2

19. Variable Atmospheric Components
Natural Sources  
Natural Factors That Affect Air Pollution  
Anthropogenic Pollution  
Benefits of the Clean Air Act

20. Natural Factors That Affect Air Pollution
Winds
Local and regional landscapes
Temperature inversion

22. Southern California Wildfires
Figure 3.8

23. Temperature Inversion
Figure 3.10

24. Anthropogenic Pollution
Carbon monoxide
Photochemical smog
Industrial smog and sulfur oxides
Particulates

25. Forests on Fire
Figure 3.12

26. Air Pollution
Figure 3.14

27. Photochemical Smog
Figure 3.15

28. 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!

29. Geosystems 7e An Introduction to Physical Geography
End of Chapter 3
Geosystems 7e
An Introduction to Physical Geography