• Source:JND
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After an intense monsoon season, the northern plains, including Delhi, are witnessing a drop in temperature earlier than usual this year. This marks the earlier arrival of winter this year, as the snowfall has already started in the higher reaches of Jammu and Kashmir and Himachal Pradesh.

The northern plains in UP, Bihar, Punjab, Himachal Pradesh, and Uttarakhand are facing a dip in temperature, especially morning chills.

While snowfall was witnessed in Srinagar last week, the higher-altitude Himachal Pradesh continued to face it throughout the week.

According to the India Meteorological Department (IMD), this weather activity is due to the La Niña effect. A senior IMD official, as quoted by the TOI, said, "Our models show a good probability of La Niña developing during Oct–Dec this year".

"La Niña is usually associated with colder winters in India. While the warming effect of climate change can offset this to some extent, winters during La Niña years tend to be colder compared to years without it. This year overall may not rank among the hottest, as monsoon rainfall has already kept temperatures under control," he added.

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What is La Niña effect?

La Niña is one of the three phases of the wider El Nino Southern Oscillation (ENSO) phenomenon. ENSO is about the change in the temperature of the sea along the central and eastern tropical Pacific Ocean.

Normally, the winds near the equator blow from South America towards Asia (East to West). These winds are called trade winds.

During the La Niña phase, these winds become stronger than usual. These strong winds push warm surface water even more westwards up to Indonesia.

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Because of the warming, more moisture evaporates, bringing heavy rainfall to the Indian subcontinent. This leads to a drop in temperature.

Along with that, La Niña shifts atmospheric patterns that helps in bringing cold air from Central Asia into northern India earlier than usual, thereby making winters colder and early.