Monsoon

Monsoon is derived from the Arabic Mausim, 'a set time,' 'season,' and was for long applied to those winds prevailing in the Indian Ocean which blow from the south-west from April to October, and from the opposite direction, or north-east, from October to April. The monsoons, in common with all winds whether regular or irregular, depend primarily on an unequal distribution of temperature and moisture over that portion of the earth's surface where they occur, which in their turn give rise to an unequal distribution of atmospheric pressure. From this unequal distribution of the mass of the earth's atmosphere winds take their rise—winds being simply the flow of the air from a region of higher towards a region of lower pressure, or from where there is a surplus to where there is a deficiency of air. The term monsoon has in recent years come to be used with a wider significance than formerly; it is now generally applied to the winds connected with all continents which are of regular occurrence with the periodical return of the seasons. The winds of Australia are thus strictly monsoonal; over the greater part of North America the prevailing winds have a well-marked monsoonal character; similarly, monsoons occur on the coasts of Brazil, Peru, North Africa, and all other regions that happen to lie between regions whose temperature, and necessarily their pressures also, differ markedly from each other at different times of the year. See WINDS.