Factors Affecting India’S Climate

What are the Factors Affecting India’S Climate

LATITUDE:

• The Tropic of Cancer passes through the middle of the country from the Rann of Kuchchh in the west to Mizoram in the east.
• Almost half of the country, lying south of the Tropic of Cancer, belongs to the tropical area.

ALTITUDE:

• India has mountains to the north, which have an average height of about 6,000 metres.
• The Himalayas prevent the cold winds from Central Asia from entering the subcontinent.
• It is because of these mountains that this subcontinent experiences comparatively milder winters as compared to central Asia.

PRESSURE AND WINDS:

The climate and associated weather conditions in India are governed by the following atmospheric condition:

• Pressure and surface winds;
• Upper air circulation; and
• Western cyclonic disturbances and tropical cyclones.
• The only part of India that receives rain from these winds are the costal area of Tamil Nadu as these winds pick up moisture from the Bay of Bengal.
• India lies in the region of north easterly winds. These winds originate from the subtropical high-pressure belt of the northern hemisphere.
• They blow south, get deflected to the right due to the Coriolis force, and move on towards the equatorial low-pressure area. These winds carry little moisture as they between from land to sea.  

Feature of the N.E. Trade Winds

• They are permanent winds.
• It blows over India during cold weather season.
• It blows from land to sea.
• It carries very less moisture and hence causes very less rainfall.
• Only the coastal area of Tamil Nadu gets rainfall form this wind.
• The pressure and wind conditions over India are unique. During winter, there is a high-pressure are north of the Himalayas. Cold dry winds blow from this region to the low-pressure areas over the oceans to the south.
• In summer, a low-pressure area develops over interior Asia as well as over northwestern India. This causes a complete reversal of the direction of winds during summer.
• Air moves from the high-pressure area over the southern India Ocean, in south-easterly direction, crosses the equator, and turns right towards the low-pressure area over the Indian subcontinent. These are known as the Southwest Monsoon winds.

Feature of South-West Monsoon:

• The upper air circulation in this region is dominated by a westerly flow. An important component of this flow is the jet stream.
• These jet streams are located approximately over 27°-30° north latitude, therefore, they are known as subtropical westerly jet streams.
• Jet stream – These are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter. A number of separate jet streams have been identified. The most constant are the mid-latitude and the sub tropical jet stream.
• In summer, the subtropical westerly jet stream moves north of the Himalayas with the apparent movement of the sun. An easterly jet stream, called the tropical easterly jet stream blows over peninsular India, approximately over 14⁰N during the summer months. 
• Western Cyclonic Disturbances – The western cyclonic disturbances are weather phenomena of the winter months brought in by the westerly flow from the Mediterranean region. They usually influence the weather of the north and north-western regions of India. Tropical cyclones occur during the monsoon as well as in October – November, and are part of the easterly flow. These disturbances affect the coastal regions of the country. Have you read or heard about the disasters caused by them on Orissa and Andhra Pradesh coast?