C.3. Solar Radiation And Heat Budget
The earth’s surface receives most of its energy in short wavelengths and incoming solar radiation is called insolation.
The amount and intensity of insolation vary during the day, in a season, and in a year.
The earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in the long waveform. This energy heats up the atmosphere from below. This process is known as terrestrial radiation.
The long wave radiation is absorbed by atmospheric gasses, particularly by carbon dioxide and other greenhouse gasses. Thus, the atmosphere is indirectly heated by the earth’s radiation.
The earth as a whole does not accumulate or lose heat. It maintains its temperature. This can happen only if the amount of heat received in the form of insolation equals the amount lost by the earth through terrestrial radiation. This balance between the insolation and the terrestrial radiation is termed the heat budget or heat balance of the earth.
The albedo of the Earth can be defined as a measure of how much light that hits a surface is reflected back without being absorbed.
[Image: Heat Budget]