Earths Orbit

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Earths Orbit
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Seasonal changes
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Which factors influence the amount of solar
energy at the top of the atmosphere at a location?
4
Apparent path of the sun
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Which factors influence the amount of solar
energy reaching the Earths surface?

• Length of day
• Area over which radiation distributes
• Path length of the radiation through the
  atmosphere before reaching the ground

Solar Zenith angle
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Global coordinates
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Global coordinates
Rotational axis
Prime meridian
N
Equator
Latitude
Longitude
45o 35' 20" N, 95o 54' 7"W
S
8
Zenith angle
Which season is this?
Summer solstice
N
Direction to the sun
A
Latitude A in degrees
minus
Tropic of cancer 23.5 degrees
S
equals
Zenith angle at latitude A
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Zenith angle
Which season is this?
Winter solstice
N
A
Direction to the sun
Latitude A in degrees
minus
Tropic of capricorn -23.5 degrees
S
equals
Zenith angle at latitude A
10
Zero zenith angle
Tropic of Cancer
Equator
Tropic of Capricorn
11
Examples for solar zenith angle
Homework
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Length of day
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Energy input at the top of the atmosphere
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Path length through the atmosphere
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Role of greenhouse gases
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