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Why do we have seasons?
Jeff Gawrych
Met 10
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DefinitionsDefinitionsInsolation –
____________________________________________________________________________________________________
Obliquity –_____________________________________
Solstice –_______________________________________________________________________________
Equinox ______________________________________________________________________
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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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147 million kilometers147 million kilometers 152 million kilometers152 million kilometers
Guess the monthsGuess the months
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What influences incoming What influences incoming solar energy?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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Sun angleSun angle
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Sun angleSun angle
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What influences incoming What influences incoming solar energy?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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This says at that the NP get more This says at that the NP get more insolation than the equator??insolation than the equator??
Why? Why? AttenuationAttenuation
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What month do you think this graph represents?What month do you think this graph represents?a) December b) March c) June d) Septembera) 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 50°S on Dec 21st?
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Further points to considerFurther 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?
