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

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

Figure 2.9

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

Chapter 2, Table 2.2 Labeled

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

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?

Chapter 2, Unnumbered Figure 1, Page 50 Labeled

Chapter 2, Unnumbered Figure 1, Page 51 Labeled

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

Insolation at Top of Atmosphere Figure 2.10

Solar Elevation at Noon (SEN)

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

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˚

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?

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?

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

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

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

How Greenhouse Effect Works https://www.youtube.com/watch?v=sTvqIijqvTg&t=29s © AMS

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