Atmospheric Energy

Atmospheric Energy

Primary source of energy- the Sun
1. sheds part of its mass as it radiates waves of electromagnetic energy and high energy particles into space.
2. Long term - accounts for all energy available to Earth.
3. Amount we receive into the atmosphere is controlled by four things.
Solar Output
1. Sun = black body = radiates and absorbs lights at the maximum rate possible
2. 1368 Wm-2 Is our solar constant (energy received at the top of the atmosphere)
  1. can be affected by up to 0.1% due to sunspots (cooler spots on the sun) which have an 11-year cycle.
3. 53% near infra-red - 39% visible light - 8% ultraviolet
Distance from the Sun
1. The eccentricity of the Earth's orbit changes in length over time over a period of about 100,000 years. From near circular to an ellipse.
  1. the eccentricity causes only minor variations to the total insolation budget but can have significant seasonal effects.
    1. if the orbit was perfectly circular there would be no seasonal variation in solar radiation there is a difference of more than 6%.
Altitude of the Sun
1. Affects the amount of radiation received
  1. The more directly overhead the more energy received per unit area.
  2. At the equator Sun's rays are concentrated, at the poles the rays spread over a wider area.
2. affected by the season, time of day and latitude
Day Length
1. The tilt of the Earth's axis produces seasonality by varying day length in both hemispheres
  1. E.g. Daylight at the poles can vary from 0-24 hours depending upon the season.
2. In summer, Earth is tilted towards the Sun (it also appears higher in the sky) giving more than 12 hours of sunlight making it warmer
  1. The tilt has been shown to vary between 21.8 degrees to 24.4 degrees over a period of 41,000 years.

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