Explain the mechanism of monsoons.
The phenomenon of monsoon refers to the seasonal reversal of winds. The offshore winds that blow from north-east direction are reversed into onshore south western winds. This phenomenon is based upon differential heating of land and ocean bodies. During summer in the Indian subcontinent, the large landmass gets heated up more rapidly than the neighbouring seas. As a result, the air above land expands and rises up. The moisture laden winds arrive on the western coast of India from the south western side and cause heavy rainfall on the windward side of the Western Ghats. The leeward side, however, receives little rain. Further rain occurs in the northern plains and north-east parts of India with the branching of the monsoon. The monsoon is also aided by the Inter Tropical Convergence Zone or monsoon trough near the equator where winds from northern and southern hemisphere merge. The landmass of the Indian subcontinent cools up around September with the sun retreating south. The ocean bodies, which lose heat slowly, retain the summer heat. The cooler high pressure air moves towards the low pressure over the ocean and causes the retreating north-east monsoon. It mainly causes rainfall along the eastern coast of India.