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Gali Sharma

Aug 10, 2014

# describe the mechanism of monsoons

describe the mechanism of monsoons

Nandita Menon

During summer, a low-pressure area develops over interior Asia as well as over north and north-western India. At the same time, there is a high-pressure system over the southern Indian Ocean. Winds move from a high-pressure area to a low-pressure area. As a result, the low-pressure system attracts the southeast trade winds of the southern hemisphere. On crossing the equator, these trade winds-due to the Coriolis force-turn right towards the low-pressure areas over the Indian subcontinent. After crossing the equator, these winds start blowing in a south-westerly direction, and enter the Indian peninsula as the southwest monsoon. As these winds blow over warm oceans, they bring abundant moisture to the subcontinent. Arriving at the southern tip of the Indian peninsula, the wind system breaks up into two branches − the Arabian Sea branch and the Bay of Bengal branch. The Arabian Sea branch hits the Western Ghats, while the Bay of Bengal branch flows over the Bay of Bengal and hits the eastern Himalayas. The coastal areas west of the Western Ghats receive much of the rainfall from the Arabian Sea Branch, while the regions lying east of the Western Ghats do not receive much rain from these winds. The north-eastern parts of the country receive much of their rainfall from the Bay of Bengal Branch. As these winds move from east to west, the moisture they carry progressively declines. As a result, rainfall decreases from east to west. The Arabian Sea branch moves towards the north-east from the south-west, and join the Bay of Bengal branch over the northern part of the country. The duration of the monsoon is between 100 to 120 days. By the end of this period, the low pressure system over north and north-west India gradually weakens, and this leads to the retreat of the monsoon winds.

To understand the mechanism of the monsoons, the following facts are important. 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. 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 area affects 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.

Syeda

Answer. To understand the mechanism of the monsoons, the following facts are important. 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. 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 area affects 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. SME Approved
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