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Geography - World & Indian (Climate)

Written By STPORTAL on Sunday, March 18, 2012 | 2:57 PM

Geography - World & Indian (Climate):

The climate of India may be described as tropical monsoon. On the basis of variations of monsoon the year is divided into four seasons.

1) The Cold Weather Season.
2) The Hot Weather Season.
3) The South West Monsoon.
4) The Retreating South West Monsoon or North East Monsoon.

1) The Cold Weather Season.

The cold weather season starts in early December. January and February are the typical cold months in most parts of India. In this period, cyclonic depressions are developed in Mediterranean region and moves to the east. This disturbances known as Western Disturbances, bring rainfall to the North West India – Punjab & Ganga plains, which is beneficial to the rabi crop. The TN coastlands also receive some rainfall during the season.

2) The Hot Weather Season:

The period March to May is a period of highest temperatures and low air pressure in Indian subcontinent,which causes moisture laden winds to be blown to these area. In Kerala and the western coast, these pre monsoon showers are called mango showers. In Assam & Bengal receive rainfall during this season from thunderstorms called Kal baishakhi or Nor’ western, In the north west of India , hot & dry winds are blown, these are called loo.

3) The South West Monsoon

Monsoon is a wind regime that is characterised by the seasonal reversal of wind direction. Although it is a global phenomenon the real monsoon rain covers India, Myanmar , Sri Lanka, Bangladesh and parts of South East Asia. According to thermal concept, after the Spring Equinox, the sun starts it apparent northward movement. Thus a massive low pressure area is created in North India due to the vast expanse of land. Thus may May-June, the pressure gradient between this low trough and adjoining seas are so great that it attracts winds even from the south of equator. The northward migration of the Inter Tropical Convergence (ITC) and Upper air circulations also affect the monsoons. As these winds are blown above the sea, it picks up moisture and causes heavy rainfall. The winds south of equator are actually south east trade winds which blow from the south east towards the north east. But it deflect towards the right after passing the equator. Nearly 80% of rains in India are caused by the south west monsoon during June – September. Except the east coast of Tamil Nadu , almost every part of India receives the N.W.monsoon rain. The S.W.monsoon strikes the Western Ghats at right angles causes Orographic precepitation on the windward side and the rainfall is scanty or even absent in the lee ward side . The Aravellis have an north south axis and fails to block the monsoon winds. This is the main reason for the absence of rainfall in Kachchh and Rajasthan region.

The Retreating South West Monsoon or North East Monsoon

The low pressure conditions of North India are transferred to the entire Bay of Bengal by the October - November. These winds pick up the moisture from the Bay of Bengal and cause rainfall in the coastal Orissa, TN and Karnataka. Some easterly depression occur in the Bay of Bengal , many of them crosses southern peninsula causes widespread rainfall and destruction of preoperties particularly in deltas of Godavary, Krishna and Cauvery.

The significance of Monsoon

India’s 70% of the population still depend on agriculture for their subsistence; About 70% of the net sown areas in the country are rain fed; Nearly 80% of rains in India are caused by South West Monsoon. So any delay, early withdrawal or inadequate rainfall in monsoon creates havoc among Indian farmers and cause a severe blow to the economy. So Indian economy is often referred as gamble in the monsoon.

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