Variation in the Net Heat Budget at the Earth’s Surface
A heat budget is a perfect balance between incoming heat absorbed by the earth and outgoing heat escaping it in the form of radiation. The earth is a whole does not accumulate or lose heat. It maintains its temperature. If they were not balanced, then Earth would be getting either progressively warmer or progressively cooler with each passing year. This balance between incoming and outgoing heat is known as Earth’s heat budget. There are variations in the amount of radiation received at the earth’s surface. Some part of the earth has surplus radiation balance while the other part has a deficit.
The figure depicts the latitudinal variation in the net radiation balance of the earth – the atmosphere system. The figure shows that there is a surplus of net radiation balance between 40 degrees north and south and the regions near the poles have a deficit. The surplus heat energy from the tropics is redistributed polewards and as a result, the tropics do not get progressively heated up due to the accumulation of excess heat or the high latitudes get permanently frozen due to excess deficit.