Short essay on Mechanism of the Indian Monsoon

The word 'monsoon' is derived from the Arabic word 'mausim' or the Malayan word 'monsin' I meaning season. It was first used by the Arabian sailors for the winds blowing in the Arabian Sea which changed in their direction with the change of season, i.e., in winter from north-east to south-west and in summer from south-west to north-east.

The term is now applied to that wind system which observes reversal in its direction (change of 180 i degrees) with the change of season. Although it: enables certain pseudo monsoon areas like southern United States, northern Australia and western Africa etc. to be included within this climatic region but fails to universally apply this criterion to those areas which fall in the transition zone of major wind (pressure) belts e.g. the Mediterreanean climatic region (between 30° -40°' Lat. and sub-polar areas (between 60°-70°Lat.).Chang-Chia-Ch'enghas given following definition: "Monsoon is a flow pattern of the general atmospheric circulation over a wide geographical area, in which there is a clearly domi­nant wind in one direction in every part of the region concerned, but in which this prevailing direction is reversed (or almost reversed) from winter to summer and from summer to winter."

According to Nieuwolt (1977), "The word monsoon is used only for wind system where the seasonal reversal is pronounced and exceeds a minimum number of degrees (120 degrees)."