A pattern of global atmospheric circulation is set up by the unequal distribution of insolation.
There are three major winds in a hemisphere :
- polar easterlies (cold and dry)
- westerlies (highly variable, contains the jet streams)
- trade winds (reliable and warm)
There are four major pressure zones in a hemisphere :
- polar high pressure zone (90° N and S latitude)
- subpolar low pressure zone (60° N and S latitude)
- subtropical high pressure zone (30° N and S latitude)
- intertropical convergence zone (equator)
Things to remember about air motion :
- Rising air cools and drops its moisture. This forms a moist low pressure zone.
- Falling air warms and absorbs moisture. This create a dry high pressure zone.