Why do we have seasons

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• Why do we have seasons?
• Jeff Gawrych
• Met 10

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Definitions

• Insolation
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  __________________________________________________
  
• Obliquity
• _____________________________________
• Solstice
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  _______________
• ______________
• Equinox
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• ______

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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 _________

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Guess the months
147 million kilometers
152 million kilometers
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What influences incoming solar energy?

• The Suns 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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Sun angle
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Sun angle
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What influences incoming solar energy?

• The Suns 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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This says at that the NP get more insolation than
the equator?? Why? Attenuation
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What month do you think this graph represents? a)
December b) March c) June d) September
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• On June 21st, at what latitude is the sun
  directly overhead at noon?
• On September 22nd, at what latitude is the sun
  directly overhead at noon?
• How many hours of daylight are present at the
  South Pole on February 20th?
• Where would you expect to have longer days 45
  N on June 21st or 50S on Dec 21st?

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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 isnt the SH summer warmer than the NH summer?