1. Solar altitude Solar altitude: angle in degrees above horizon
Variations in solar altitude and daylength drive seasonality ☼
30 degrees

2. Solar Altitude (con’t.)
Solar altitude = 90 – [the number of degrees of latitude that separate place of interest from the declination (subsolar point)]
The subsolar point can be determined for the solstices and equinoxes using data already provided, shown here again:
Approximate Date
Northern Hemisphere
Location of the Subsolar Pt. (declination)
December 21
December (winter) Solstice
23.5° S latitude
(Tropic of Capricorn)
March 21
March Equinox
Equator (0°)
June 21
June (summer) Solstice
23.5° N
(Tropic of Cancer)
Sept. 22
September equinox

3. Solar altitude calculation (con’t.)
If the date that you need the subsolar point for is not in the previous table, use an analemma.
Example: What is the solar altitude for Salem, Oregon on June 21?
latitude of place of interest:  N
latitude of subsolar point:  N
Difference: 
Therefore, solar altitude is calculated as = 68.5
Show animation if time allows

4. Structure of Atmosphere
Layers by temperature, starting at surface:
Troposphere: falling temps
Stratosphere: rising temps
Mesosphere: falling temps
Thermosphere: rising temps

5. Profile of Atmosphere
Figure 2.17

6. Atmospheric Temperature Structure: Troposphere
Surface to ~11 mi
90% of mass of atmosphere
Global average lapse rate – cools at 3.6 °F/1000 ft. It cools because its greenhouse gasses absorb terrestrial longwave radiation (primary way that the troposphere is heated) and these gasses become less abundant with incr. alt. (also cools because turbulent heat transfer is most effective near ground, less so higher up)
Local temp change observed at a particular time (Environmental lapse rate) varies.

7. Temperature Structure (cont)
Stratosphere
(11 to 30 mi)
Temp. increases w/ elevation because ozone in upper part absorbs shortwave uv radiation from the sun
Mesosphere
(30 to 50 mi)
Temp. declines w/ elevation, (few gasses here to absorb outgoing longwave radiation or incoming shortwave rad.)
Thermosphere
(50 mi) outwards
Temp. rises w/ elevation, due to solar excitation of individual molecules
Aurora borealis caused by charged particles of solar wind colliding with gasses.

8. Atmospheric Pressure
Key concept: atmospheric pressure decreases with increases in height.
Figure 2.18

9. Skip this slide About barometers:

10. Know in order of abundance: Nitrogen, Oxygen, Argon, Carbon Dioxide
Composition of the Homosphere (lowest 50 miles – where the mix of most major gasses is similar throughout)
Know in order of abundance: Nitrogen, Oxygen, Argon, Carbon Dioxide
Figure 2.19

11. Earth’s Protective Atmosphere
Figure 2.21

12. Atmospheric Function
Much protection from harmful radiation is given in stratosphere, mesosphere, and thermosphere
Ozonosphere (part of Stratosphere)
Ozone (O3) absorbs UV energy

13. Natural Factors That Affect Air Pollution
Winds can disperse pollution or bring it in from elsewhere
Valleys can concentrate pollution
Temperature inversions (when temperature in the troposphere increases rather than decreases with height) concentrate pollutants near ground

14. Temperature Inversion
Figure 2.24

15. Air Pollution Death http://timesofindia. indiatimes

16. Optional slide Photochemical Smog
Figure 2.26

17. Benefits of the Clean Air Act
Compliance costs borne directly by business, consumers, and government entities
Benefits enjoyed across all sectors of society, including health, economic, & environmental (ag. forestry, fishing).
Net financial benefit (benefits – costs) large
Estimated 206,000 fewer deaths by 1990
But still, about 200,000 premature deaths annually in the US come from air pollution
What are leading sources of pollution here?