New Delhi: The south-west monsoon has set in over Kerala on Sunday, three days ahead of its normal onset date of June 1, the weather office said.
The south-west monsoon is considered the lifeline of India's agri-based economy.
"South-west monsoon has set in over Kerala on Sunday, May 29, against the normal date of onset of June 1," India Meteorological Department (IMD) Director General Mrutyunjay Mohapatra said.
Earlier, the IMD had forecast onset over Kerala on May 27 with help from remnants of Cyclone Asani that struck the Bay of Bengal a fortnight ago. The forecast had a model error of four days.
However, the influence of the remnant weather systems that lingered over the southern peninsula petered out.
The southwestern summer monsoons occur from July through September. The Thar Desert and adjoining areas of the northern and central Indian subcontinent heat up considerably during the hot summers.
This causes a low pressure area over the northern and central Indian subcontinent. To fill this void, the moisture-laden winds from the Indian Ocean rush into the subcontinent. These winds, rich in moisture, are drawn towards the Himalayas.
The Himalayas act like a high wall, blocking the winds from passing into Central Asia, and forcing them to rise. As the clouds rise, their temperature drops, and precipitation occurs. Some areas of the subcontinent receive up to 10,000 mm (390 in) of rain annually.
The monsoon accounts for nearly 80% of the rainfall in India. Indian agriculture (which accounts for 25% of the GDP and employs 70% of the population) is heavily dependent on the rains, for growing crops especially like cotton, rice, oilseeds and coarse grains.
A delay of a few days in the arrival of the monsoon can badly affect the economy, as evidenced in the numerous droughts in India in the 1990s.
(with inputs from PTI)