Question

Which wind accounts for rainfall along the Malabar Coast?

Answer 1

Malabar Coast gets rains from South-West Monsoon Winds. Since it is first region to hit by south west monsoon , malabar coast receives heavy rainfall in the months of June and July. The seasonal alteration of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons.

The climate of India is described as the ‘monsoon’ type. The Monsoon type of climate is found in South Asia and South-East Asia.

Advancement of Monsoon in India

• The duration of the monsoon is 100 to 120 days. The monsoon advances rapidly but withdraws slowly.
• Generally, by the first week of June, the monsoon arrives at the southern tip of the Indian peninsula.
• It gets divided into 2 branches – Bay of Bengal branch and Arabian sea branch.
• The southwest monsoon sets in over the Kerala coast by 1st June.
• By 10th and 13th June they reach Mumbai and Kolkata respectively.
• The Southwest monsoon covers the entire subcontinent by mid-July.
• By the first week of June, the Bay of Bengal branch arrives in Assam.
• These winds get deflected to the West over Ganga plains, by the Himalayan mountains.
• By mid-June, the central part of the country and the Saurashtra-Kuchchh region gets covered by the Arabian sea branch of the monsoon winds.
• The Bay of Bengal branch and Arabian Sea branches of the monsoon merge over the northwestern part of the Ganga plains.
• Generally, by the end of June, the Bay of Bengal branch brings rainfall to Delhi.
• Eastern Rajasthan, Punjab, Western Uttar Pradesh, and Haryana experience the monsoon generally by the first week of July.
• Himachal Pradesh and the rest of the country receive rainfall generally by mid-July.

Southwest Monsoon Winds – Facts

• Southwest monsoon winds are responsible for bringing widespread rainfall over mainland India.
• Southwest monsoon winds carry moisture when they blow over warm oceans.
• Over the Southern Indian Ocean, the air moves in a South easterly direction. Air moves from the high-pressure area to the low pressure area. Once the air crosses the equator it turns towards Indian subcontinent which has low pressure areas.
• Westerly flow dominates the upper air circulation in this region.
• Jet Stream is an important component of this Westerly flow.
• These Jet streams are known as subtropical westerly jet streams, since these streams are located approximately over 27°-30° north latitude.
• Over India, these jet streams blow south of the Himalayas, all through the year except in summer.
• The subtropical westerly jet stream moves north of the Himalayas, during summer, with the apparent movement of the sun.
• During the summer months, approximately over 14°N, a sub-tropical easterly jet stream blows over peninsular India. These are Easterly jet streams.
• Westerly flow creates the western cyclonic disturbances which are experienced in the North-Western and Northern parts of India.

Intensity of Rainfall in West Coast

The intensity of rainfall over Western Coast is dependent on 2 major factors.

• Along the eastern coast of Africa, the position of the equatorial jet stream.
• The offshore meteorological conditions.

Withdrawal of Monsoon

• Withdrawal of monsoon is a gradual process.
• By early September, monsoon begins its withdrawal from Northwestern states.
• From the Northern half of the Peninsula, the monsoon withdraws completely by mid-October.
• The monsoon withdraws from the rest of the country by early December.
• From the islands, the Monsoon begins and completes its withdrawal from the first week of December to the first week of January.