➤ The climate of India can be broadly describe as Tropical Monsoon Climate.
➤ Derived from the Arabic word ‘Mausam’ monsoon implies a seasonal reversal in the wind direction through the year.
➤ The monsoon regime emphasises the unity of India with the rest of south-east Asia region.
➤ The meteorologists usually recognise the following four seasons:-
(i) Hot weather season,
(iii) South-West Monsoon season, and
(iv) The Season of retreating Monsoon.
➤ Summer is India’s hottest season.
Summer season starts in March with day times temperatures exceeding 30° C. Coastal India as well as the southern states of Tamil Nadu and Kerala experience high humidity. By May, most of interior India experience very high temperature (40° C).
➤ Warm land surface creates large area of low pressure over north western India. This creates an onshore wind bringing the moisture laden maritime air from Indian Ocean to the land.
➤ Southwest Monsoons: The southwest monsoons supplies over 80 per cent of India’s annual rainfall. It consists of two arms, the Bay of Bengal arm, and the Arabian Sea arm. Both arms are attracted to the low pressure area over the Thar desert in Rajasthan.
➤ The monsson makes its presence felt by the end of May. It starts around the 29th May, hitting the Andaman and Nicobar Islands in the Bay of Bengal. It strikes the mainland of Kerala on June 1. By 9th June, it hits Mumbai and Delhi by 29th June. By first week of July, the entire country experiences rain. Predictably, Southern India receives more rainfall than Northern India.
➤ The Bay of Bengal branch moves in the northwest direction whereas the Arabian Sea arm moves in the northeast direction.
➤ During this season, cyclones occur, causing widespread devastation to coastal regions.
Cherapunji and Mawsynram in Meghalaya, the world’s wettest place, receive rainfall above 300 cms annually.
➤ The monsoons start, withdrawing by the last week of August.
By mid September, it has withdrawn from Mumbai and by October, the southwest monsoons have completely withdrawn from
➤ Northeast Monsoons: After the withdrawal of the monsoons, the northeast monsoons begin by November. Supplying 20 per cent of India’s rainfall it doesn’t cover the entire country but only the States of Tamil Nadu, West Bengal, Arunachal Pradesh, Karnataka, Kerala and Meghalaya.
➤ Cold mountain air travelling along the Brahmaputra river brings rain to the northeast region of India.
This picks up moisture over the Bay of Bengal resulting in heavy rain in southern India.
FACTORS RESPONSIBLE FOR INDIAN MONSOON
1. The differential heating and cooling of land water creates low pressure on the landmass of India while the seas around experience comparatively high pressure.
2. The shift of the position of Inter Tropical Convergence Zone
(ITCZ) in summer, over the Ganga plain.
3. The presence of the high-pressure area, east of Madagascar, approximately at 20°S over the Indian ocean.
4. The Tibetan plateau gets intensely heated during summer, which result in strong vertical air currents and the formation of low pressure over the plateau at about 9 km above sea level.
5. The movement of the westerly jet stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer.