I. Global patterns of mean temperature are influenced by a number of factors, but the primary influence is the effect of latitudinal variation in radiation balance , which is related to changing sun angles and daylength associated with the seasons. In tropics, incoming solar radiation exceeds outgoing terrestrial radiation.
Tropics experience a radiation surplus .
In polar regions, terrestrial radiation losses exceed solar radiation gains. Polar regions experience a radiation deficit . The midlatitudes are a region of active heat transport, out of the tropics to higher latitudes. It is this differential radiational heating that powers our atmosphere, causing it to remain in ceaseless fluid motion, attempting to re-balance the radiational imbalance. Least annual variation in equatorial latitudes, due to constant day lengths and high sun angles.