Discuss the mechanism of monsoons. Explain all the factors.
Answers
Answer:
During summer season as land gets heated up, the air rises and the low-pressure area is created on the land and on the other hand high-pressure area is created in the Indian Ocean. Air moves from high-pressure areas to low-pressure areas. The low-pressure land system attracts south-east trade winds but after crossing equator due to Coriolis force, winds turn right towards the low-pressure areas over the Indian subcontinent. These winds start blowing in a south-westerly direction and enter the Indian peninsula as the southwest monsoon. As it reaches India monsoons are divided into two branches namely - Arabian Sea branch and Bay of Bengal branch.
Explanation:
Monsoons are seasonal winds (Rhythmic wind movements or Periodic Winds) which reverse their direction with the change of season.
The monsoon is a double system of seasonal winds – They flow from sea to land during the summer and from land to sea during winter.
Indian Monsoons are Convection cells on a very large scale.
India receives south-west monsoon winds in summer and north-east monsoon winds in winter.
South-west monsoons are formed due to intense low pressure system formed over the Tibetan plateau.
North-east monsoons are associated with high pressure cells over Tibetan and Siberian plateaus.
The southeast trade winds in the southern hemisphere and the northeast trade winds in the northern hemisphere meet each other near the equator.
The meeting place of these winds is known as the Inter-Tropical Convergence Zone (ITCZ).
This is the region of ascending air, maximum clouds and heavy rainfall.
The location of ITCZ shifts north and south of equator with the change of season.
In the summer season, the sun shines vertically over the Tropic of Cancer and the ITCZ shifts northwards.
The southeast trade winds of the southern hemisphere cross the equator and start blowing in southwest to northeast direction under the influence of Coriolis force.
These displaced trade winds are called south-west monsoons when they blow over the Indian subcontinent.
The front where the south-west monsoons meet the north-east trade winds is known as the Monsoon Front. Rainfall occurs along this front.
In the month of July, the ITCZ shifts to 20°- 25° N latitude and is located in the Indo-Gangetic Plain and the south-west monsoons blow from the Arabian Sea and the Bay of Bengal.
The ITCZ in this position is often called the Monsoon Trough (maximum rainfall).
The seasonal shift of the ITCZ has given the concept of Northern Inter-Tropical Convergence Zone (NITCZ) in summer (July – rainy season) and Southern Inter-Tropical Convergence Zone (SITCZ) in winter (Jan – dry season).
NITCZ is the zone of clouds and heavy rainfall that effects India.
In normal circumstances, when the tropical eastern South Pacific Ocean experiences high pressure, the tropical eastern Indian Ocean experiences low pressure. Such changes in the pressure conditions over the southern oceans also affect the monsoon.
But in certain years, there is a reversal in the pressure conditions. In this case, the eastern Pacific Ocean has lower pressure compared to the eastern Indian Ocean. This periodic change in pressure conditions is known as the Southern Oscillation or SO.