Question.
What are the controls affecting the climate of India?
( Chapter - 4 Climate, Cass 9 NCERT Contemporary India -I )
Answer.
In general, there are six major controls of the climate of any location-latitude, altitude[ height from sea level], pressure and wind system, distance from the sea, ocean currents, and relief features [ mountain, hills, plateau, plains].
There are three major controls affecting the climate of India-latitude, altitude, and pressure and winds.
Latitudinal controls of the climate of India:
The Tropic of cancer ( 23.5 degrees north latitude] passes almost the middle of India. The region lying north of the tropic of cancer has a subtropical climate and the region lying south of the tropic of cancer has a tropical climate. So India has both tropical and subtropical climates.
Altitudinal controls of the climate of India:
India has a great Himalayan range in the north which has an average height of about 6000 meters. So the Himalayan prevents the cold winds from central Asia from entering the Indian subcontinent, so India feels milder winter as compared to the same latitude of the other part of the world.
Himalayan also prevent monsoon winds to go further northward and helps precipitation in India.
Pressure and winds control the climate of India:
The climate and associated weather conditions in India are largely governed by the following four atmospheric conditions-Pressure and surface winds, upper air circulation, western cyclonic disturbances, and tropical cyclones.
The pressure and Surface winds system of India is unique.
During winter, cold and dry winds blow from north of the Himalayas toward the Indian Ocean.
In summer, monsoon winds blow from the ocean toward the Indian subcontinent. During summer, low pressure developed over northwestern India and the Tibetan plateau, this leads to the reversal of winds, and air moves from high pressure [ Indian ocea] to low pressure [ land] as southwest monsoon.
Upper air circulation in India is dominated by the western subtropical jet stream. Westerly jet streams blow approximately 25 to 30 degrees north latitude in the south of the Himalayas throughout the year except during monsoon season. The subtropical westerly jet stream is responsible for western disturbance and winter rainfall in the northern and northwestern part of India and it is responsible for bringing monsoon winds close to the Himalayas as it moves from south of the Himalayas to north of the Himalayas during the monsoon season. When the subtropical westerly jet stream moves from south of the Himalayas to the north of the Himalayas, the easterly subtropical jet stream came up in existence and flows above 14 degrees north latitude over peninsular India and it helps the distribution of monsoon rainfall throughout India.
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