The northeast monsoon has well and truly arrived with Chennai recording heavy rainfall for the third consecutive day on Tuesday. Tamil Nadu’s capital has not recorded such rainfall in the last 72 years, as the regional MeT recorded 8.4 cm of rain.
Overnight rains lashed the state capital’s neighbouring districts and other regions of Tamil Nadu, leading to flood-like situation. Some parts of the city and suburbs witnessed waterlogging, resulting in traffic congestion and slow movement of vehicles.
Schools have been closed in Chennai, Kancheepuram, Tiruvallur, Chengelpet, Nagapattinam, Thanjavur and Tiruvarur districts. Light to moderate rainfall is expected to continue in coastal and Cauvery delta regions of the state.
Monsoon in India
According to the National Geographic, the basic definition of monsoon is “seasonal change in the direction of the prevailing, or strongest, winds of a region”. These are most often associated with the Indian Ocean. The southwest (summer) monsoon and the northeast (winter) monsoon determine most of India’s climate.
What is the southwest or summer monsoon?
The southwest, or the summer, monsoon is the lifeline of India as it decides the state of agricultural productivity in the country and, in turn, the economy. While its pattern keeps changing, its set time of arrival, as per geographical estimate, is June with withdrawal in September. Most of the country receives almost 75 per cent of its rainfall in this time period, and sometimes more.
This year, the monsoon arrived in the first week of June but spilled onto October with heavy showers in the north and northwest of India. Hence, it can be said global weather patterns are also affecting the monsoon’s four-month time period, which has now been officially recognised by the India Meteorological Centre. Three years ago, the weather department pushed withdrawal dates from the north and northwest to the first or second week of October. This year, however, the monsoon’s complete withdrawal was stretched to the third week on October 23.
What is the northeast or winter monsoon?
Now, for the northeast monsoon, or the winter monsoon – this is, as of now, causing heavy rainfall in Tamil Nadu. Lesser known than its rainy summer equivalent, this monsoon lasts between October and December. It mostly affects Tamil Nadu and Rayalaseema region of Andhra Pradesh, accounting for only 11 per cent of the country’s total rainfall.
How are the two monsoons in India different from each other?
GEOGRAPHICAL FACTORS: The summer monsoon accounts for heavy showers than the winter, which is its less enthusiastic cousin. It is defined by warm and moist air from the southwest Indian Ocean that blows toward countries like India, Sri Lanka, Bangladesh, and Myanmar at the end of winter. The summer monsoon brings a humid climate and torrential rainfall to these areas, as per the National Geographic.
It is caused by an intense low-pressure system forming over the Tibetan Plateau as a result of intense heating during the summer season. The monsoon winds during this time travel in a southwesterly direction after crossing the equator and are so named.
As for the winter, or northeast, monsoon, it is less powerful than the summer monsoon in Southeast Asia. This is due to the Himalayas preventing much of the wind and moisture of the monsoons from reaching the coast, as per National Geographic. The mighty and young fold mountains also prevent cool air from reaching South India and Sri Lanka, which keeps them warm all year.
This monsoon enters India from the northeast and is so named. Northeast monsoon winds blow from the sea to land. Low-pressure systems, depressions, and cyclones cause associated rainfall.
FUNCTIONS: The significance of the southwest monsoon for India is much larger. Agricultural cycles in the country are defined by the southwest monsoon as many areas still do not have proper irrigation systems. The summer monsoon increases the levels of water in natural as well as man-made water resources. All agricultural activity, including animal farming, is associated with the summer monsoon. Even electricity is generated from hydroelectric power plants that depend on water collected during the monsoon. In short, the monsoon has often been called India’s “true finance minister” as the country’s economy is largely affected by the quality of rain received during this monsoon. A weak monsoon will mean a poor yield across most sectors, while a strong monsoon can cause irreparable damage with destroyed crops and flood-like situation or even devastating floods.
In India, Tamil Nadu receives the bulk of its annual rainfall during the northeast monsoon between October and December. The state receives about 48 per cent of its annual rainfall of 914 mm during this time. Rainfall is also received over parts of Puducherry, Kerala and Karnataka.
Scientists say the northeast monsoon is the prime reason behind intense tropical cyclones. As the southwest monsoon does for most of the country, the northeast monsoon affects agricultural activity in south peninsular India. Seasonal rainfall has an impact on rice and maize productivity in Tamil Nadu and Andhra Pradesh.
(With PTI inputs)
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