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Explained: What is La Nina and how it is making winter colder in India

Explained: What is La Nina and how it is making winter colder in India

Explained: What is La Nina and how it is making winter colder in India
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By CNBCTV18.com Dec 20, 2021 12:58:05 PM IST (Published)

While climate change is unleashing extreme events across the globe, the harsh winter conditions in India is due to the La Niña effect that has been emerging in the Pacific Ocean.

After witnessing the worst phases of intense heat and heavy rainfall this year, India is now gripped by freezing cold. Most parts of central and northern India have already seen a significant drop in minimum temperatures in December.

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The India Meteorological Department (IMD) on Sunday warned that severe cold wave conditions will prevail over north Rajasthan, Punjab, Uttar Pradesh, Uttarakhand, Himachal Pradesh, north Madhya Pradesh Haryana, Chandigarh, Delhi and Jammu and Kashmir till December 21. The minimum temperature dropped to 4.6 degrees Celsius in the Delhi on Sunday morning, the lowest recorded so far this season, the weather monitoring agency reported.
While climate change is unleashing extreme events across the globe, the harsh winter conditions in India are due to the La Niña effect that has been emerging in the Pacific Ocean.
What is La Niña?
The La Niña and El Nino are oceanic and atmospheric phenomena that typically develop between April and June and gain strength during October and February. Though these events prevail for 9-12 months, they can last for up to two years.
Under normal conditions, trade winds or the winds guiding the ocean currents in the Pacific Ocean blow west along the equator. This causes warm water from South America to move towards Asia. Cold water rises from the depths of the ocean to replace the displaced warm water. However, two opposing climate patterns, El Niño and La Niña, break these normal conditions.
El Niño, which means a little boy in Spanish, weakens the trade winds and corresponds to the warmer phase. During this phenomenon, warmer currents are pushed back east, toward the west coast of the America. A large part along the equator experiences above-normal ocean temperature. The heat dissipating from the ocean rises into the atmosphere and causes warmer air temperatures in the Pacific, thereby leading to warmer global air temperatures.
On the other hand, La Niña, which means ‘a girl’ in Spanish, is responsible for an opposite climatic pattern. During this phase, a strong easterly current pushes the water towards the west, which cools the ocean surface.
Earlier, the El Niño had developed in 2018-2019, while the La Niña impact was witnessed during the winter of 2020-2021 and 2017-2018.
“For the upcoming winter season, which extends from December 2021 through February 2022, there is an 87 percent chance of La Niña," US-based National Oceanic and Atmospheric Administration had said in October.
How does it impact India?
La Niña is responsible for bringing cold air from Siberia and South China to the Indian subcontinent, which results in a north-south low-pressure system when it interacts with the tropical heating conditions here. The cold conditions associated with these troughs can envelope the southern parts of India as well and can extend till Tamil Nadu. However, they do not affect Northeast India.
In the winter months, the La Nina causes a very cold wave-like jet stream to flow across Afghanistan, Iran and the Hindu Kush mountains. These strong and cold winds impact the degree of cold in India.
Earlier, the weather phenomenon had led to the unexpected heavy rains in October. It had also caused a delayed withdrawal of the southwest monsoon from the country on October 25, which was the seventh-most delayed retreat since 1975.
In January and February, temperatures in India are likely to touch 3 degrees Celsius in some northern areas before recovering, Bloomberg reported.
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