1. 1 Why do we have seasons? Jeff Gawrych Met 10

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3. 3 Definitions Insolation – ________________________________________________________ ____________________________________________ Obliquity – _____________________________________ Solstice – ________________________________________________________ _________ ______________ Equinox ________________________________________________________ ________ ______

4. 4 Distance from the Sun NOT the main reason we have seasons However, it is a factor… Depends on eccentricity Def. Presence of an atmosphere Earth is closest to sun in _________ Earth is furthest from sun in _________

5. 5 147 million kilometers 152 million kilometers Guess the months

6. 6 What influences incoming solar energy? The Sun’s angle of incidence: A.k.a Overhead angle High Angle Low Angle Length of time the Sun shines each day: Long days can be deceiving…

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8. 8 Sun angle

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11. 11 Sun angle

12. 12 What influences incoming solar energy? The Sun’s angle of incidence: Lower sun angle, Higher sun angle, Length of time the Sun shines each day: Summer season, Winter season,

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14. 14 This says at that the NP get more insolation than the equator?? Why? Attenuation

16. 16 What month do you think this graph represents? a) December b) March c) June d) September

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18. 18 On June 21 st, at what latitude is the sun directly overhead at noon? On September 22 nd, at what latitude is the sun directly overhead at noon? How many hours of daylight are present at the South Pole on February 20 th ? Where would you expect to have longer days; 45 ° N on June 21 st or 50°S on Dec 21 st ?

19. 19 Further points to consider You may be able to tell which was north is by looking at local vegetation. Why? The southern hemisphere (SH) receives slightly more solar radiation than the northern hemisphere (NH), during summer. Why isn’t the SH summer warmer than the NH summer?