Monsoon

Definition

The seasonal reversal of wind direction over the Indian subcontinent, driven by the differential heating of land and sea, which brings India most of its annual rainfall.

Key points

• Caused by the differential heating of the Asian landmass and the surrounding oceans, reversing the winds seasonally.
• South-west monsoon (June to September) brings about three-quarters of India's rain, in two branches: the Arabian Sea branch and the Bay of Bengal branch.
• Western Ghats cause heavy rain on the windward western coast by orographic lift, with a rain shadow to the east.
• The retreating or north-east monsoon (October to December) brings rain to the Tamil Nadu coast.
• Phenomena such as the El Nino can weaken the monsoon.

Why it matters for CAPF

The monsoon mechanism, branches, and orographic effects are recurring geography facts, often as assertion-reason items linking the Western Ghats to coastal rainfall.

Common confusion

South-west (summer, main rain) versus north-east (winter, mainly Tamil Nadu) monsoon; and windward heavy rain versus leeward rain shadow.

Parent note

indian monsoon and climate