‘La-Nina phenomenon’: reason for the increase in heat-wave in India

‘La-Nina phenomenon’: reason for the increase in heatwave in India

The recent La-Nina phenomenon is adding to the heatwave in India. La Nina is a seasonal phenomenon. It occurs in the Pacific Ocean. It is also known as “Little Girl”.

La Nina is generally considered to be a positive contributing factor to India’s monsoon; however, it is believed that the increasing heat wave events in India are actually being driven by La Nia.

General Conditions:

  • Where the land temperature in India starts rising in March. At the same time, generally the western disturbances or the humidity of the Mediterranean region hinders it. It brings rain in North and West India.
  • But for these currents to reach India, they require a wide difference in temperature between the latitudes of Europe and India.
  • During La Nina in winter, a north-south pressure system is established over India. Generally it affects the trade winds that bring rain to India.
  • However, this year, due to the weak La Nina, this temperature difference was less. Therefore, the Western Disturbances coming into India were also weak. Because of this, the warm westerly winds that seldom brought rain in India were dominant.

What are El Nino and La Nina years?

El Nino year is an unusual event of unusually warm waters of the eastern Pacific Ocean. It occurs at intervals of two to seven years.

How it affects the Indian monsoon:

  • The area of rising warm wind/precipitation is shifted towards the central/east Pacific. The flow of this warm wind is reduced over the Indian Ocean / mainland of India. This creates an area of high pressure. Due to this, there is no rain on the mainland of India.
  • As the east wind weakens, warm water begins to flow towards South America.

A La Nina year is a cold current phenomenon, which usually occurs after a warm El Nino event. The warm equatorial ridge between the coast of South America and Oceania cools.

How this phenomenon helps in the Indian monsoon:

In the western Pacific, the warm wind/high rainfall area strengthens the monsoon winds. This causes heavy rainfall in India.

Source – The Hindu

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