3. Discuss the mechanism of Indian Monsoon. (10 marks| 150 words)
India monsoon is a monsoon wind in its true sense. It is active in Indian subcontinent which undergoes complete reversal of wind direction .
Factors precursor to Indian Monsoon setup
- After spring equinox, sun moves towards northern hemisphere.It causes ITC to shift northwards to Tibetan Plateau
- Huge heating of the plateau creates low pressure zone there
- North-western Indian subcontinent gets heated and becomes low pressure zone.
- the low pressure zones attract winds from the southern sphere. They become south-westerly after crossing equator.
- Westerly sub-tropical jet stream shifts northwards. The tropical easterly develops in upper atmosphere of India. This cause increased atmospheric pressure over Indian Ocean.
Monsoon in Action
- Monsoon divides in to two arms namely Arab Sea branch and Bay of Bengal branch. The former enters western part of subcontinent and causes heavy rainfall in western part of western ghat. The same branch passes parallel to Aravali range without rainfall.
- Bay of Bengal branch gets divided into two parts. One enters in north-eastern region. the second moves along Himalayan range towards north-west India. The shifting of ITC results in erratic behavior of monsoon.
Retreating of Monsoon
- With summer solstice the sun as well ITC shifts southwards. There is an increase in atmospheric pressure on the land parts of the Indian subcontinent. That over Indian Ocean declines. This leads to reversal in wind direction to become north-easterly. This is north-east or winter monsoon.
Phenomenon of Indian monsoon is the result of cyclic movement of sun on latitudes. The Tibetan plateaus, mountain ranges and location of ITC facilitate its mechanism and decide the distribution of the rainfall over the region.