1. Seasonality and the Greenhouse Effect
Current News and Weather
Seasonality
Solar Elevation at Noon
Greenhouse Effect
For Next Class: Read Ch. 3

2. Discussion Questions
1. How does latitude influence incoming solar radiation and temperature?

3. Figure 2.9

4. Seasonality Two important seasonal changes
Sun’s altitude – angle above horizon or Solar Elevation at Noon (SEN)
Day length

5. Chapter 2, Table 2.2 Labeled

6. Annual March of the Seasons
Winter solstice – December 21 or 22
Subsolar point Tropic of Capricorn
Spring equinox – March 20 or 21
Subsolar point Equator
Summer solstice – June 20 or 21
Subsolar point Tropic of Cancer
Fall equinox – September 22 or 23

7. Discussion Questions
1. How does latitude influence incoming solar radiation and temperature? 2. Where on Earth would 24 hours of sunlight be observed on or around June 21? Why?

8. Chapter 2, Unnumbered Figure 1, Page 50 Labeled

9. Chapter 2, Unnumbered Figure 1, Page 51 Labeled

11. 11:30 P.M. in the Antarctic
Figure 2.16

12. Insolation at Top of Atmosphere
Figure 2.10

13. Solar Elevation at Noon (SEN)

14. Solar Elevation at Noon (SEN)
SEN is the angle of the noon sun above the horizon
SEN = 90˚ - ArcDistance
ArcDistance = number of degrees of latitude between location of interest and sun’s noontime vertical rays
If the latitude of location of interest and sun are in opposite hemispheres, add to get ArcDistance
If they are in the same hemisphere, subtract from the larger of the two values

15. SEN Example What is the SEN on June 21 for Boone (36 N)
SEN = 90 – ArcDistance
Where are the sun’s noontime vertical rays?
ArcDistance = 36 – 23.5
ArcDistance = 12.5
SEN = 90 – 12.5
SEN = 77.5˚

16. SEN Exercises
What is SEN in Punta Arenas (53º S) on June 21? December 21?
What is SEN in Cayambe, Ecuador (0º) on June 21? March 21?
What is SEN in Barrow, Alaska (71º N) on June 21? December 21?

17. Discussion Questions
1. How does latitude influence incoming solar radiation and temperature?
2. Where on Earth would 24 hours of sunlight be observed on or around June 21? Why?
3. What is the greenhouse effect and why is it important?
4. What are the major greenhouse gases?

18. Terrestrial Radiation
Greenhouse Effect
Heating of Earth’s surface and lower atmosphere caused by strong absorption and emission of infrared radiation (IR) by certain atmospheric gases
known as greenhouse gases
Similarity in radiational properties between atmospheric gases and the glass or plastic glazing of a greenhouse is the origin of the term greenhouse effect
© AMS

19. Terrestrial Radiation
Greenhouse Effect
Responsible for considerable warming of Earth’s surface and lower atmosphere
Earth would be too cold without it to support most forms of plant and animal life
© AMS

20. Terrestrial Radiation
Greenhouse Gases
Water Vapor is the principal greenhouse gas
Clear-sky contribution of 60%
Other contributing gases:
carbon dioxide (26%)
ozone (8%)
methane plus nitrous oxide (6%)
© AMS

21. How Greenhouse Effect Works
© AMS

22. Feedback on Today Name one thing you learned today.
What questions do you have?