1. Chapter 3: Introduction to the Atmosphere
Image courtesy of cimss.ssec.wisc.edu

2. Importance of Earth’s Atmosphere
Provides oxygen
Weather (short-term) & Climate (long-term)
Protection from UV radiation & meteors
Temperature Control
Water (hydrologic cycle)

3. Size of Earth’s Atmosphere
Atmosphere uniformly surrounds Earth
Held down by Earth’s gravity
Extends up to 10,000 km from the surface
More than 50% of the total mass is below 6 km
Figure 3-2

4. Composition of the Atmosphere
Two primary gas types
Permanent
Oxygen & Nitrogen
Neither plays a major role in atmospheric processes
Variable
Water Vapor
Carbon Dioxide
Ozone
Play significant role in weather & climate
Permanent gases make up over 95% of total atmosphere

5. Water Vapor in the Atmosphere
Amount of water vapor in the atmosphere varies from 0-4%
Water vapor transports heat & regulates temperature

6. Carbon Dioxide in the Atmosphere
Carbon dioxide also regulates temperature
Amount of atmospheric CO2 is about 0.039%, but it’s rising
Greenhouse Effect

7. Composition of the Atmosphere
Particulates
Non-gaseous particles which exist in the atmosphere
Human-induced & natural types
Some are hygroscopic
Some reflect or absorb sunlight
Figure 3-4

8. Vertical Structure of the Atmosphere
Thermal Layers (temp. alternates from one layer to the next)
“Sphere” = entire layer
“Pause” = upper boundary of a layer
Troposphere—lowest layer; weather occurs here; tropopause
Thickest at Equator & thinnest at Poles due to the Earth’s rotation & convection
Stratosphere—stagnant air; ozone layer; stratopause
Mesosphere—middle of atmosphere; meteors burn up; mesopause
Thermosphere—“heat”
Exosphere—transitions into space
Figure 3-5

9. Vertical Structure of the Atmosphere
Air Pressure
“Weight” of the air
Decreases with height at non-constant rate
Low-levels compressed by air above, so surface pressure is higher
90% of atmosphere is in lowest 16 km
Figures 3-7 & 3-8

10. Measuring Atmospheric Pressure

11. Vertical Structure of the Atmosphere
Figure 3-9
Composition
Homosphere—uniformly mixed
Heterosphere—layered
Ozonophere—AKA ozone layer; high concentration of O3
Ionsophere—electrically charged ions; source of auroras

12. Depletion of the Ozone Layer
Natural Ozone (O3)
Naturally produced by UV radiation to shield us from UV radiation
Introduction of impurities into the atmosphere at rapid pace
Received international attention in recent years
Figure 3-11

13. Depletion of the Ozone Layer
Chemistry of Ozone Layer depletion
Reduction/destruction of ozone by CFCs
The “Hole” in the Ozone layer
Mainly affects polar regions
Figure 3-13
Figure 3-12

14. Human-Induced Atmospheric Change
Figure 3-15: Santiago, Chile Smog
Primary vs. secondary pollutants
Primary pollutants
Particulates
Carbon monoxide
Nitrogen compounds
Sulfur compounds
Secondary pollutants
Photochemical smog
Ozone
Los Angeles, CA Smog

15. Weather and Climate
Weather—short-term atmospheric conditions for a specific area
Meteorology
Climate—aggregate long-term weather conditions
Climatology
Weather vs. climate

16. Weather & Climate: Latitude
Latitude is the most important/significant control of weather and climate
Heat received across Earth’s surface from sunlight is a function of latitude
Figure 3-16

17. Weather & Climate: Distribution of Land & Water
Distinction between maritime & continental climates
Dallas, TX, & San Diego, CA, have very different climates
Maritime climates = humid Continental climates = dry
N. (Land) Hemisphere vs. S. (Water) Hemisphere
Figure 4-24

18. Weather & Climate: General Circulation of the Atmopshere & Oceans
General circulation of the atmosphere
Semipermanent wind pattern on Earth
Varies with latitude
General circulation of the oceans
Oceanic broad-scale semi-permanent motions
Help transfer heat
Figure 3-17

19. Weather & Climate: Altitude & Topography
All 4 controls of weather and climate affected by altitude
Topographic barriers
Can drastically alter climate due to orographic change in wind patterns
Windward side vs. Leeward side
Figure 3-20

20. Weather & Climate: Storms
Control weather & climate through atmospheric modification
Some storms are prominent enough to affect climate
Figure 3-21

21. Weather and Climate Coriolis effect
Rotation of Earth modifies path of forward motion of free-moving objects over great distances
Curves to the right in the N Hemisphere
Curves to the left in the S Hemisphere
Deflection greatest at the poles; zero at the equator
Proportional to speed of the object
Only influences direction of an object; no influence on speed of an object

22. Weather and Climate
Coriolis effect
Figure 3-22

23. Summary
Earth’s atmosphere is a shallow “ocean” of air that uniformly surrounds the Earth
The atmosphere consists of many permanent and variable gases
The gas with the highest concentration in Earth’s atmosphere is nitrogen (78%)
The atmosphere has various vertical structures that describe it
Five main spheres make up the thermal atmosphere
The homosphere and heterosphere describe the gas composition of the atmosphere at different heights
Most auroral activity occurs in the ionosphere
Human activity has modified the atmospheric composition through pollution and ozone depletion
Weather and climate, while related, involve atmospheric conditions on different time scales
Many controls exist that modify the four primary weather elements
The Coriolis effect is an apparent force that exists due to the rotation of Earth