The Mechanism of the Indian Monsoon
The climate of India is strongly influenced by monsoon winds. This wind system reverses its course seasonally and its pattern is permanent in nature. This helps the traders conventionally sail over the ocean and Arabs are the first to name this wind system monsoon.
The Monsoon is experienced in the tropical area roughly between 20°N and 20°S. The Mechanism of the Indian monsoon can be understood with the help of the following important facts. The different heating and cooling of land and water create a low pressure on the landmass of India while the seas around experience comparatively high pressure.
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).
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 affect the Indian Monsoon. 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 level.
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. Apart from this, it has also been noticed that changes in the pressure conditions over the southern oceans also affect the monsoon.
The South-West monsoon is the most significant feature of the Indian climate. The season varies from less than 75 days over west Rajasthan to more than 120 days over the south-western regions of the country contributing to about 75% of the annual rainfall. The monsoon is influenced by global and local phenomena like El-Nino, Northern hemispheric temperatures, sea surface temperatures, show cover etc.
The monsoon rainfall oscillates between active spells associated with widespread rains over most parts of the country and breaks with little rainfall activity over the plains and heavy rains across the foothills of the Himalayas. Heavy rainfall in the mountainous catchments results in flooding over the plains. However, very uncomfortable weather due to high humidity and temperature is the feature associated with the break of the monsoon.