Monsoon is a unique climatic factor that differentiates south Asian countries; particularly India and parts of Australia and Africa, from the rest of the world. The term refers to seasonal moisture-rich winds that soak the lands they blow upon, with water that at once heals, but also is potent enough to destroy. The Indian subcontinent is predominantly affected by changes in these winds, which have a southerly and a westerly component. Combined together they constitute the Southwest Monsoon, the harbinger of life and the much needed rains. Almost 70 per cent of India’s food production depends on these rains, so are the rivers that flow through the country’s domestic pipelines.India Gets most of its rainfall by South-West Monsoon.
SOUTH WEST MONSOON:
The southwest monsoon brings rains towards the end of summer as the high pressure built in the Indian Ocean pushes the wind masses towards the low pressure formed on land. It’s the temperature variation between the sea and the landmass – sea air being cooler and land being warmer – that causes the action.Also,we have to take an important factor called Temperature Gradient into consideration. It is the Temperature Variation Between The landmass and the surrounding sea.
ACTION OF SOUTH WEST MONSOON IN INDIA:
The southwest monsoon arrives in two branches: the Bay of Bengal branch and the Arabian Sea branch. The latter extends toward a low-pressure area over the Thar Desert and is roughly three times stronger than the Bay of Bengal branch. The southwest monsoon typically breaks over Indiasn Territory by around 25 May, when it lashes the Andaman and Nicobar Islands in the Bay of Bengal. It strikes the Indian mainland around 1 June near the Malabar Coast of Kerala. By 9 June, it reaches Mumbai; it appears over Delhi by 29 June. The Bay of Bengal branch, which initially tracks the Coromandal Coast northeast from Cape Comorin to Orissa, swerves to the northwest towards the Indo-Gangetic Plain. The Arabian Sea branch moves northeast towards the Himalayas. By the first week of July, the entire country experiences monsoon rain; on average, South India receives more rainfall than North India. However, Northeast India receives the most precipitation. Monsoon clouds begin retreating from North India by the end of August; it withdraws from Mumbai by 5 October. As India further cools during September, the southwest monsoon weakens. By the end of November, it has left the country.
The southwest monsoon, a four-month period when massive convective thunderstorms dominate India’s weather, is Earth’s most productive wet season. A product of southeast trade winds originating from a high-pressure mass centered over the southern Indian Ocean, the monsoonal torrents supply over 80% of India’s annual rainfall. Attracted by a low-pressure region centered over South Asia, the mass spawns surface winds that ferry humid air into India from the southwest. These inflows ultimately result from a northward shift of the local jet stream, which itself results from rising summer temperatures over Tibet and the Indian subcontinent. The void left by the jet stream, which switches from a route just south of the Himalayas to one tracking north of Tibet, then attracts warm, humid air. The main factor behind this shift is the high summer temperature difference between Central Asia and the Indian Ocean. This is accompanied by a seasonal excursion of the normally equatorial intertropical convergence zone, a low-pressure belt of highly unstable weather, and northward towards India.
KEY ASPECTS AND BARRIERS:
1.Strikes at western ghats;and gives rainfall to the western most regions;while western ghats sheilds the inner region so Deccan plateau becomes a dry land.
2.moves parallel with the eastern ghats and produce no rainfall until it strikes at Bangladesh.
3.Another current enters at kutch peninsula and gives medium rainfall to the Indo-Gangetic plains.
The South west monsoon is also called as a Sea breeze and produces more rainfall than North East monsoon.The maximum rainfall will be recorded by state of Kerala,While Mumbai receives the next.