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what is the mechanism of monsoon

The monsoons are experienced in the tropical area roughly between 20° N and 20° S. The mechanism of the monsoons can be understood from following facts ::

(a) The differential heating and cooling of land and water creates low pressure on the landmass of India while the seas around experience comparatively high pressure. 

(b) The shift of the position of Inter Tropical Convergence Zone (ITCZ) in summer, over the Ganga plain (this is the equatorial trough normally positioned about 5°N of the equator – also known as the monsoon- trough during the monsoon season). 

(c) The presence of the high-pressure area, east of Madagascar, approximately at 20°S over the Indian Ocean. The intensity and position of this high-pressure area affects the Indian Monsoon. 

(d) The Tibetan plateau gets intensely heated during summer, which results in strong vertical air currents and the formation of high pressure over the plateau at about 9 km above sea llevel. 

(e) The movement of the westerly jet stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer.

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during the summer the global heat belt shifts over northern hemisphere therefore due to many reasons the land gets heated up and water has a lower temperature

  • the heating of land and water (land is more hotter than water)
  • the shift of the inter tropical convergence zone(place where trade winds merge) over the ganga plains creating low pressure
  • presence of a high pressure region over madagascar(southern hemisphere)
  • the blowing of the easterly jet stream and shift of the westerly jet stream north of himalayas
  • the southern oscillation(before when there was higher pressure over the pacific indian ocean was hot but due to the el nino warm ocean current the pacific is hot and indian ocean is comparitively cool)

so there is high pressure over the south indian ocean and low pressure over the northern plains so air moves from south to north when they enter the northern hemisphere the coiollus force  turns them to the right.as these winds move over the warm oceans they gather a lot of moisture.at the end of may it reaches the tip of the subcontinent it is divided into two branches the arabian sea branch cause rain in western ghats and reach mumbai by 10th june the bay of bengal branch reaches north eastern states by the first week of june then the himalayas send them into the west the rainfall decreases from east to west and both merge over ganga plains.

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