The monsoon is a seasonal reversal of winds that brings rain to India. The word comes from the Arabic word 'mausim', meaning season. About 75% of India's rainfall comes from the monsoon, which makes it vital for farming and a key exam topic.
The Southwest Monsoon
- It blows from the sea to the land between June and September.
- It enters India through two branches: the Arabian Sea branch and the Bay of Bengal branch.
- It usually reaches Kerala around 1 June.
- It brings the main rains to most of India.
The Northeast Monsoon
From October to December, the winds reverse and blow from land to sea. This retreating monsoon brings rain to the Tamil Nadu coast and southeastern India.
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Mechanism of the Monsoon
In summer, the land heats up and forms a low pressure area over northwest India. Winds blow from the high pressure over the ocean to this low pressure, carrying moisture. The Inter-Tropical Convergence Zone (ITCZ) plays a major role.
Factors Affecting the Monsoon
- El Nino weakens the monsoon and can cause drought.
- La Nina usually strengthens the monsoon.
- The Jet Streams and the position of the ITCZ also affect rainfall.
Quick Revision Points
- The word monsoon comes from 'mausim' (season).
- The southwest monsoon (June-September) brings most rain.
- It has Arabian Sea and Bay of Bengal branches.
- It reaches Kerala around 1 June.
- The northeast monsoon rains over Tamil Nadu.
- El Nino weakens and La Nina strengthens the monsoon.
- About 75% of rainfall is from the monsoon.