4.7. General Circulation of the Atmosphere

As discussed earlier that wind is the result of pressure gradient which is largely caused by differential heating of the earth. Winds in the atmosphere are neither unidirectional nor have a same pattern as we go up in the atmosphere. In fact, winds may change their direction and intensity multiple times within same day. Largely, wind movement in the atmosphere may be classified into three broad categories:

♤ Primary circulation: it includes planetary wind systems which are related to the general arrangement of pressure belts on the earth’s surface. The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. In fact, it is the primary circulation patterns which prepare the broad framework for the other circulation patterns.

♤ Secondary circulation: it consists of cyclones and anti-cyclones, monsoon

♤ Tertiary circulation: it includes all the local winds which are produced by local causes such as topographical features, sea influences etc. Their impact is visible only in a particular area.