Figure 5 – heat energy budget by latitudes

2.1. Latitudinal Heat Balance

Although the earth as a whole maintains balance between incoming solar radiation and outgoing terrestrial radiation. But this is not true when we observe at different latitudes. Heat budget at latitudinal level is non-zero. As previously discussed, the amount of insolation received is directly related to latitudes. Some part of the earth has surplus radiation balance while the other part has deficit.

Figure 5 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 400 N & S degrees and the regions near the poles have a deficit. This in theory should mean that tropical areas should get steadily warmers, and the Arctic and Antarctic even colder. But such is not the case. The surplus heat energy from the tropics is redistributed pole wards 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. This transfer of surplus heat from tropics to polar region is being performed by atmospheric and oceanic circulations such as winds and ocean currents. According to one estimate, about 75 per cent of heat transfer is carried out by atmospheric circulation and the remaining 25 per cent by the ocean currents. In fact, winds and ocean currents are produced due to imbalance of heat.