Climate — Class 11 Geography

India has a hot monsoonal climate marked by the seasonal reversal of winds, with broad unity but many regional variations in temperature and rainfall (from over 1,080 cm at Mawsynram to under 9 cm at Jaisalmer). India's climate is controlled by latitude, the Himalayas (which shield the subcontinent from cold northern winds and trap the monsoon), distribution of land and water, distance from the sea, altitude and relief. The monsoon mechanism involves the differential heating of land and sea, the northward shift of the Inter Tropical Convergence Zone (ITCZ), the southeast trades crossing the equator to become the south-west monsoon, and the easterly jet stream. The south-west monsoon sets in over Kerala by 1 June and engulfs the country by mid-July; a "break in the monsoon" is a dry spell during the rainy season. The meteorologists recognise four seasons: the cold weather season, the hot weather season (with local storms like the "loo", mango showers and nor’westers), the south-west monsoon season (with the Arabian Sea and Bay of Bengal branches) and the retreating monsoon season (October–November, bringing cyclones to the eastern coast). El Nino influences monsoon forecasting. The chapter also notes the impact of the monsoon on India's economy and the concern of global warming. (Refer to the map in the NCERT textbook.)