Factors affecting Climate of India
The factors that have a great impact on the climate of India are:
1. Monsoon winds: There are two monsoon winds that blow over India, one is the moist south-west monsoon wind in the summer and the other is the dry north-east monsoon winds in winter.
These two different types of monsoon winds have been caused mainly because of land and water contrast. The mainland of the Indian subcontinent and Asia get quickly heated in summer while the surrounding extensive water in the south, the Indian Ocean remains cool in summer.
Land get heated quickly because only the surface is heated (as land is a bad conductor of heat) so temperatures rise swiftly. Water on the other hand takes a longer time to get heated because the whole mass of water has to be heated for it to change temperature. Similarly in winter the land becomes cold faster while the seas in the south remain comparatively warm.
So, in summer the temperature over the land is 5° to 8 ° higher than the water to the south whereas in winter the temperature over south and central Asia is 8° to 14° less compared to the waters of the Indian Ocean. Therefore, in summer low pressure is created over land while high pressure occurs over water. In winter the opposite occurs. This gives rise to winds moving in opposite directions in summer and winter. Bering seasonal winds they are called monsoon winds.
- North-East Monsoon Winds: In winter the land is cooler in central and southern Asia compared to the oceans in the south. Thus, high pressure occurs over land while the oceans have low pressure. Cool dry winds from the land move southwards to the low pressure in the seas. Due to the rotation of the earth the winds get deflected to their right as according to Ferrel’s law, while moving from the north to the south. Thus, these winds form the North-East Monsoon winds. They blow from snow covered land areas of Central Asia. So the north-east monsoon winds are cold and dry. When this wind blows over India, the temperatures are lowered over the whole of India. The Himalayas act as a barrier top these cold winds of Central Asia so that their impact is not so severe. Compared to South India the temperature falls more rapidly in North India. In the mountain areas of Uttaranchal, Himachal Pradesh, Jammu and Kashmir etc. temperatures fall below (-) 10°C to (-) 40°C. Heavy snowfall occurs. In winter the coastal regions of Tamil Nadu received rainfall from these north-east monsoon winds. This is because the dry north-east winds from Central Asia pick up large amounts of moisture from the Bay of Bengal before reaching the Coromandel Coast. According to some geographers, winter rainfall in Tamil Nadu occurs because of the retreating south-west monsoon winds. In winter, rainfall occurs in North Western India mainly due to western disturbances.
- South-West Monsoon Winds: Low pressure forms over land in Central and Southern Asia in the summer season. Winds move into this low pressure region from the adjacent high pressure region of the Indian Ocean. Due to the rotation of the earth these winds moving from the south to the north are deflected to their right as according to Ferrel’s Law. They thus form the south-west monsoon winds. These south-west monsoon winds are heavily laden with moisture as they move from the oceans in the south. The peninsular of India just out in the Indian Ocean and divide the winds into two branches – that which blows over the Arabian Sea is called the Arabian Sea branch and the other that blows over the Bay of Bengal is called the Bay of Bengal branch of the monsoon winds. The monsoon begin suddenly with the arrival of these winds which are accompanied by thunder, lightning, heavy rainfall etc. The sudden arrival of the monsoon with all this fanfare is called the burst of the monsoon. In the whole of India rainfall occurs widely during this time. The total annual rainfall in India is mainly influenced by these rains which contribute 75-80% of the total rainfall. Maximum rainfall occurs in the Eastern Himalayas and windward side of the Western Ghats. Indian is mainly an agricultural country and most of the agriculture is dependent on the rains provided by the south-west monsoon winds. Thus the economy of India is directly affected by the arrival duration, distribution and withdrawal of this monsoon wind.
The north-east monsoon wind cools the country further while the south-west monsoon winds bring rainfall and together they control the climate of India.
This is notice in the arrival and departure of these two monsoon winds which have created the cycle of seasons in India as:
- Summer is the season previous to the arrival of the south-west monsoon winds.
- Rainy season is the arrival of the south-west monsoon winds.
- Autumn is the retreat or withdrawal of the south-west monsoon winds and
- Winter is the arrival of the north-east monsoon winds.
2. Latitudinal location: The Tropic of Cancer (23.5°N) passes through the middle of India thus dividing India into the tropical region to the south of it and the subtropical and temperate region to the north of it. This implies, the region south of the tropic of Cancer is warmer compared to the north as it is nearer to the Equator.
3. Location of the Himalayas, Western and Eastern Ghats: Relief forms an important factor that affects the climate of India. The high Himalayan Mountain in the north act as a barrier to the south-west monsoon winds forcing the winds to give most of its rainfall in India before crossing the Himalayas. The cold winds in winter from Central Asia are mainly obstructed from coming into India by these high Himalayas. So the severity of winter in India is not that intense. The Western and Eastern Ghats on either side of the Peninsular in South India force the monsoon winds to give plenty of rainfall in the coastal regions. Again, the eastern slopes of the Western Ghats fall in the rain-shadow area as the Western Ghat obstructs the monsoon winds and get heavy rainfall on the western slopes.
4. Altitude: Temperature decreases with increase in height at the rate of 6.5°C per 1000 meters difference in height. The high peaks of the Himalayas are thus always covered by snow. Shimla is therefore cooler than Delhi as it lies at a higher elevation. Ooty in the Nilgiris in the Western Ghats is cool even in summer because of its height though it lies near the equator.
5. Distance from the Sea: Compared to land water takes longer to heat or to cool. The Peninsular of India is surrounded by water in the east, west and south. Therefore, compared to north India south India has a moderate climate. As north India lies far from the sea the difference in summer and winter temperatures is very high. The cli8mate in north India is of extreme type.
6. Desert Region of Rajasthan: In summer the Desert Region of Rajasthan experiences very high temperature creating a very low pressure. This extreme low pressure attracts the monsoon winds from the Indian Ocean. As these winds blow over the oceans they become most and cause heavy rainfall over the whole of India.