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Lecture

# Solar radiation, the sun, etc

2 pages25 viewsWinter 2011

Department
Geography
Course Code
GGR100H1
Professor
Joseph Leydon

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Geography Lecture #2
January 13, 2011
â€¢Earth rotates eastwards daily on its own axis (rotation)
â€¢Elongated/elliptical orbit around the sun
â€¢Aphelion- the point where the earth is furthest from the sun
â€¢Perihelion- point when the earth is closest to the sun
The Sun
â€¢6000 K surface
â€¢enough energy to fuse atoms together-> nuclear fusion
â€¢sun radiates energy at the speed of light in a spectrum
â€¢sun emits charged particles (solar wind)
â€¢It is energy emitted as waves of electric and magnetic oscillations
â€¢Electromagnetic radiation is emitted by all matter with a temperature
â€¢Q (energy emitted from radiation) is proportional to the Temperature
of the object
â€¢Wavelength of radiation is inversely related to surface temperature
(hotter objects -> shorter wavelengths)
Example
â€¢Comfortable human skin temperature = 33 degrees Celsius
â€¢Average human surface area ~ 1.8m2
â€¢895 watts emitted (1 watt= 1 joule per second)
â€¢similar to 9 household light bulbs
â€¢we give off emissions in the infrared part of the spectrum (heat)
â€¢absorption of different wavelengths by gasses in the atmosphere,
gamma and xrays get absorbed at 80 km from the earths surface
How much insolation does Earth intercept?
â€¢At the equator or anywhere where the sun is directly overhead is where
â€¢Sub-solar point: where the sun is directly overhead ^
â€¢The same light energy diffused over a larger area reduces intensity
â€¢Averaged daily latitudinal energy imbalance (Net R) at the top of the
atmosphere -> spatial variation
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