Monsoons dominate India’s climate. They can be defined as strong, violent winds which change direction with the season. Monsoon winds tend to blow from cold to warm regions. During winters they blow from the land towards the sea and in summers they blow from the sea towards the land.
Indian winters are mostly hot and dry. Monsoon winds carry a little moisture and they blow from the northeast. The mighty Himalayas act as a barrier preventing cold air from passing onto the subcontinent.
Summer monsoons reach the subcontinent from the southwest. They carry moisture from the Indian Ocean resulting in heavy rains from June to September. Severe rainfalls may trigger landslides and other disasters. Despite these potential dangers, people eagerly wait for summer monsoons in India.
As the hot air over land rises, it creates an area of low pressure, allowing moist ocean air to blow towards the land. Air gets condensed as it gets lifted. Monsoons are more like sea and land breezes.
Onset of Monsoon
Monsoon usually begins in India in the first week of June. To start off with, it rains heavily over Kerala and coastal Karnataka. The monsoon then spreads to the Peninsular region and finally reaches the southwestern and southeastern parts of the country by June 10. It usually starts raining in Rajasthan by 1st July and it showers in Kashmir by July 15th. At times the onset of Monsoon is delayed in Kerala, having an impact on the rainfall patterns across the country.
Periods of Active Monsoon
In the first stage, rainfall is experienced in the west coast up to Konkan and Peninsular India and also in the northeast region.
At times, the monsoon over the peninsular region can be delayed by a few days. In the second stage, rain advances into the Gangetic valley up to Uttar Pradesh and also into Gujarat.
Following this, after a gap of 7 days, rain further advances westwards and northwards. The active monsoon period usually ranges from July to September.
Break Monsoon Conditions
As the monsoon trough moves northwards to the foothills of Himalayas, the rainfall is largely limited to the northeastern region of Assam and surrounding regions. The rest of the country usually goes dry during this period.
The northeast monsoon is responsible for providing rainfall to Peninsular India from October-December. For example, the state of Tamil Nadu depends on northeast monsoon rains for its agriculture. It is hard to figure out any clear-cut distinction between the withdrawal of southwest monsoon and the onset of northeast monsoon.
Withdrawal of Monsoon
By 15 December, the monsoon usually retreats from the Indian Peninsula. Duration of the monsoon varies in different parts of the country. While rainfall is experienced for around 122 days over the Kerala coast, the duration of rainfall is as low as 45 days in dry and arid regions of western Rajasthan.
It begins in the month of June and ends by September or mid-October. Moisture laden winds get divided into the Arabian Sea Branch and the Bay of Bengal Branch on reaching the southernmost point of Indian Peninsula.
Kerala is the first state in India to receive rainfall from the southwest monsoon.
Bay of Bengal branch of southwest monsoon heads towards northeast India and Bengal. The village of Mawsynram in Shillong is one among the wettest places on the earth.
Monsoon is responsible for 80 per cent of rainfall in India. As we all know, Indian agriculture is heavily dependent on rainfall. A delay in rainfall badly affects our economy; India has already witnessed several droughts due to lack of rainfall.
Northeast monsoon or retreating monsoon is defined as the cold wind which sweeps down Himalayas and the Indo-Gangetic plain, which moves towards the vast spans of Indian Ocean, predominantly to the south of Deccan Peninsula.
Tamil Nadu receives about 50 to 60 percent of its rainfall in the form of northeast monsoon.
Several natural and human induced climatic factors such as the El-Nino effect, deforestation and thinning of the ozone layer are responsible for the failure of monsoon.
Livelihoods of millions of people in our country are dependent on the monsoon season!
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Answer) First week of June.
Answer) El-Nino effect, deforestation and thinning of ozone layer.