Question

Give reasons for the following.

India receives southwest monsoon from June to September.

Answer 1

1. Thermal low over northern India: Intense summer sun produces very high land temperatures (especially over the Thar desert and Indo‑Gangetic plain), creating a strong low‑pressure trough that attracts winds from the ocean. This thermal contrast is the primary driver for the seasonal onshore flow.
2. Change in wind direction (wind reversal): Southern‑hemisphere SE trade winds are attracted toward the summer low; after crossing the Equator they are deflected by the Coriolis force into south‑westerly winds that blow onto India. These become the moisture‑laden southwest monsoon.
3. Moisture sources and branching: The Arabian Sea and Bay of Bengal provide abundant moisture. The monsoon divides into an Arabian Sea branch and a Bay of Bengal branch; together these supply widespread rainfall over the peninsula and plains during June–September.
4. Orographic enhancement and timing: Mountain ranges (Western Ghats, northern hills) force uplift of the moist south‑westerlies producing heavy orographic rain once the winds arrive the monsoon typically “breaks” over Kerala around June 1 and advances north and east through June July.