Monsoon Winds

The Monsoon is a type of Periodic wind that blows in a particular season of the year. The word monsoon is derived from the Arabic word mousim, meaning season. However, though the monsoon is a seasonal wind, it is so much associated with rain that it invariably means the rainy season. The Monsoon winds are similar to the land and sea breezes. They are the land and sea breezes on a large scale, but they are a seasonal, rather than a daily phenomenon.

Monsoon winds are basically caused by the unequal heating or cooling of the land and sea which results in a pressure difference. So winds blow from high pressure to low pressure areas as the on-shore wet monsoon in summer and the off-shore dry monsoons in winter.

During the summer months of May, June and July, the interior of larger land masses, especially in Asia, become extremely hot by the vertical rays of the sun, which causes the development of low pressure areas. At the same time, during those months, the air over the Indian Ocean is relatively cool, which results in high pressure over the sea. As a result, the wind from the Indian Ocean blow northward and north-westward into Asia and bring heavy rainfall to South-East Asia. As the winds blow south-west, they are known as the South-West Summer Monsoon.

The reverse occurs during the winter season when the big land mass in the interior of Asia, stretching from Central Asia up to the north-west Indian plain, becomes very cold and develops an extensive high pressure centre. At the same time, a low pressure zone develops in the Indian Ocean and the prevailing cold surface winds move out from Asia towards the surrounding seas as the Winter Monsoon. As these winds are cold and dry, they are incapable to produce rain, unless there is a passage of cyclonic storms. However, after crossing the seas these winds bring some rainfall over the adjoining land. The Southern Coromandel Coast of Tamil Nadu in India, the Vietnamese Coast, and the west coast of Japan get rain from the winter monsoons. Over Sothern Asia, the winter monsoon winds blow as the North East Trade Winds, and they blow from October to March.

The monsoon blows over India, Pakistan, Bangladesh, Myanmar, Sri Lanka, China, Japan, the Arabian Sea, and the Bay of Bengal. It is the most important feature of the climate in Asia, especially in the Indian subcontinent. .Although they are associated with Northern Australia, the Southern United States, and South Africa as well, they are not as strong as in Asia.