Atmospheric Circulation

Atmospheric circulation is the large-scale movement of air, and the means by which thermal energy is distributed on the surface of the Earth. The circulation of wind in the atmosphere is driven by the rotation of the earth and the incoming energy from the sun.

The Hadley cell is the circulation cell that is nearest to the equator.  Winds are light at the equator because of the weak horizontal pressure gradients located there.  The warm surface conditions result in locally low pressure.  The warm air rises at the equator producing clouds and causing instability in the atmosphere.

The Walker circulation is an east-west circulation.  Over the eastern Pacific Ocean, surface high pressure off the west coast of South America enhances the strength of the easterly trade winds found near the equator.