Slide 8: The atmosphere III: Horizontal transfers
Because of the earth's curvature, more radiation falls in equatorial regions than at the poles. Thus, between 40°N and 35°S, there is a net radiation surplus, whilst near the poles there is a deficit (the earth radiates more energy outwards than it receives. (Trewartha & Horn, 1980).
To restore equilibrium, an interchange of heat from tropics to poles occurs through movement of air. If this did not occur, the tropics would be on average 15°C warmer than current, and the poles would be 25°C colder! (Barry & Chorley, 1992)
This latitudinal transfer of energy occurs in several ways, involving the movement of sensible heat (convection processes caused by heating, rising and dispersion of surface air), latent heat (evapotranspiration processes involving evaporation of water vapour from the oceans and transpiration from land plants) and ocean circulation (discussed later).
There are balances for this movement, in terms of mass balance - for each packet of air that moves polewards, a similar quantity moves towards the tropics, setting up circulation cells.
The rotation of the earth sets up a coriolis effect which also affects the movements of the air masses.
These energy fluxes are the principal components of the climate - hence, actions which interfere with the fluxes necessarily affect the climate.
Barry, R.G. & Chorley, R.J., 1992. Atmosphere, Weather & Climate, 6th edn. Routledge, London. 392pp.
Trewartha, G.T. & Horn, L.H., 1980. An Introduction to Climate. New York: McGraw-Hill.