Explain how the south-west monsoon develops over India.

1. 1 · Define it. The monsoon is the seasonal reversal of winds over India.
2. 2 · Summer heating. By May the northern plains heat up to 45 °C or more. Hot air rises and a low pressure trough forms from Jaisalmer to Balasore.
3. 3 · Higher pressure at sea. The Indian Ocean heats more slowly, so higher pressure lies over it.
4. 4 · Winds reverse. Moist air moves from sea to land, from the south-west, opposite to the winter north-east winds. The jet stream's shift north helps.
5. 5 · Arrival. The winds reach Kerala in the first week of June with a burst of heavy rain and cover India by mid-July.
6. 6 · Draw if asked. On an outline map, draw one arrow from the Arabian Sea onto the west coast and one from the Bay of Bengal into the north-east.
7. 7 · Close in one line. So unequal heating of land and sea drives the monsoon.

Scoring tip: Use the chain heat, low pressure, wind, rain. Leaving out the pressure step usually costs a mark.