General Circulation of the Atmosphere:

The principle drivers are:

• differential heating of the earth's surface
• the rotation of the Earth

Think of this physically as a rotating differentially heated fluid that is trying to find some kind of equilibrium. Generally speaking that will produce large sale quasi stable cell circulation. The response of the Earth is the production of Hadley Cells. Hadley cell confluence circulation produces the major areas of subsidence and uplift on the Earth.

Descending air (subsidence) is warm, dry air amd this is responsible for major deserts at +/- 25-35 degrees latitude. Convergent uplift (at -15 to + 15 and 40-60 degrees produces tropical moisture and temperate rains respectively. Note that the poles are areas of subsidence, hency they are extremely dry.

Differential Heating:

Leads to a surplus of heat in equatorial regions and a deficet in higher latitudes. The rotating Earth redstributes this heat via equatorial to polar movement through the hadley cells.




The basic response of the equatorial regions excess heat budget is deep convection in which there are various length scales of activity (convection is a physically difficult problem - we will start to deal with it later)



This is one of the reasons that the Indian Ocean is so active - there is a lot of heat flux there.