What is the mechanism of Indian monsoon

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https://www.meritnation.com/ask-answer/question/explain-the-mechanism-of-monsoons/climate/1881267

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The following facts are important to understand the mechanism of Indian monsoon:

Differential Heating and Cooling of Land and Water

a. Due to this lower pressure is found on the landmass.

b. High pressure is found on the water bodies/seas and oceans around India.

Shift in the position of Inter Tropical Convergence Zone (ITCZ)

a. Inter Tropical Convergence Zone is the equatorial trough (lower pressure area). It is normally positioned at 5° north of equator.

b. During summer it shifts its position to the Ganga plain, and is also known as monsoon trough, during the monsoon season.

Presence of High Pressure Area, East of Madagascar

b. The intensity and position of this high pressure area affects the Indian monsoon.

Intensely Heated Tibetan Plateau

a. Tibetan plateau gets intensely heated during summer.

b. It results in the strong vertical currents.

Westerly Jet Stream and Tropical Easterly Jet Stream

a. Westerly Jet stream moves to the north of the Himalayas.

Southern Oscillation

a. Changes in the pressure conditions over the southern oceans also affect monsoons. Normally when the tropical Eastern south Pacific Ocean experiences high pressure, the tropical Eastern south Indian Ocean experiences low pressure.

b. This periodic change in pressure conditions and wind is known as the Southern Oscillation or so.

EL Nino  It is a warm ocean current that flows past the Peruvian coast, in place of the cold Peruvian current every 2 to 5 years.

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 the other answer may be:

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 joins 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.

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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 joins 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.

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Hi,

Winds blow from high pressure belt to low pressure belt. The mechanism of monsoon is also affected by the same principle.

1)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 .

2)The Inter Tropical Convergence Zone (ITCZ) is a broad trough of low pressure in equatorial latitudes. This is where the northeast and the southeast trade winds converge. This zone shifts due to the apparent movement of the sun.

3)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.

4)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.

5)Movement of westerly jet stream to the north the Himalayas and the tropical easterly jet stream over the Indian peninsula.

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The mechanism of increasing Indian monsoon rainfall following major El Nino &150; Southern Oscillation (ENSO) events has been investigated using an atmospheric general circulation model (AGCM) coupled to a thermodynamic mixed layer. In our simulations, El Nino produces a warming of the troposphere and intensification of convection over the equatorial south Indian Ocean during the early spring. The anomalous convection progresses northwards up to the subcontinent of India during the early monsoon season (Jun-Jul). This progression occurs via anomalous moisture transport by the mean cross-equatorial flow, even though the intensity of the monsoon circulation decreases. Our simulations also suggest an intraseasonal evolution of the mechanisms associated with anomalous summer monsoon rainfall conditions over the north Indian Ocean and Indian subcontinent following a winter El Nino. During the early period of the monsoon (Jun-Jul), moisture transport by the mean cross-equatorial flow is the main source for increasing monsoon rainfall. As the moisture perturbation homogenizes during the late period (Aug-Sep), large-scale moisture transport weakens. Instead, anomalous surface latent heat fluxes associated with north Indian Ocean warming increase boundary layer moist static energy and support above normal rainfall. Additional idealized experiments demonstrate that the winter- early spring El Nino-induced Indian Ocean warming and subsequent local boundary layer moist processes are mostly responsible for increasing the monsoon rainfall. However, the strength of the monsoonal cross-equatorial flow is strongly modulated by the contemporaneous remote forcing from the eastern equatorial Pacific (Nino3 area), where El Nino's residual (decaying) signal remains. We discuss competing effects of the north Indian Ocean warming versus the anomalous subsidence on the Indian monsoon rainfall.

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