The word monsoon is believed to be derived from the Arabic word ‘mausim', meaning a shift in wind or season.
Monsoon is the seasonal change in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea.
Monsoons are often associated with rainy seasons in the tropics, the areas of Earth within 23.5 degrees latitude of the equator and the subtropics, areas between 23.5 and about 35 degrees latitude, both north and south.
During summer, the sunlight heats the surfaces of both land and the oceans, but land temperatures rise more quickly. As the land's surface becomes warmer, the air above it expands and an area of low pressure develops. The ocean however remains at a relatively lower temperature, and the air above it retains a higher pressure. This difference in pressure causes sea breezes to blow from the ocean to the land, bringing moist air inland. This moist air rises to a higher altitude over land and then it flows back toward the ocean (thus completing the cycle). However, when the air rises, and while it is still over the land, the air cools. This decreases the air's ability to hold water, and this causes precipitation over the land.
Monsoons are usually a call for a celebration at first, because its a relief for after the long 6 month dry season.
The Indian monsoon has a reputation for appearing suddenly as soon as the subtropical jet stream is out of the way. As the air is forced to rise over the foothills of the Himalayas, it causes constant, heavy rains, often resulting in destructive flooding in hilly areas and the over-populated cities of the country.
