Background Information: Atmospheric Heat Budget
The average temperature of the earth has remained approximately constant at about 15 degrees Celsius during the past century. It is therefore in a state of radiative balance, emitting the same amount of energy as it is receiving. One way of studying atmospheric processes is to construct an energy budget. Budgets are useful to indicate where material or energy comes from (sources) and where it goes (sinks). The enormous amount of energy available to the atmosphere is very apparent during storms. The Atmospheric Heat Budget shows where the atmospheric heat energy comes from and where it goes.
Practically all this energy ultimately comes from the sun in the form of the electromagnetic spectrum also known as electromagnetic radiation or electromagnetic waves. The sun's surface is extremely hot and radiates energy over a wide spectrum of wavelengths. The amount of heat energy received from the hot interior of the earth and from the stars is quite negligible by comparison.
It has been estimated that approximately 99 percent of the sun's radiation is contained in the wavelength range of 0.15 A (micron: 1 u = 10-1 in) to 4.0 u. If the wavelength of the radiation is short, the penetrating power of the wave is very high. Solar radiation is therefore known as short wave radiation.
Directly beneath the sun, the top of the atmosphere receives approximately 20 kcal per square meter per minute (1 cal = 4.18 joule and 1 kcal = 1000 cal = 4.18 x 101 joule). The incoming energy is distributed over the earth's surface as the earth rotates about its axis every 24 hours.
