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Opinion

November was the coldest in 71 years, IMD data shows

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November 2020 was the coldest in Delhi in 71 years, with global weather events such as La Niña and the absence of western disturbances, as well as local ones such as less rain in September and the absence of cloud cover, contributing to an average minimum temperature of 10.2 degrees. Celsius degrees.

Normally average minimum temperatures in November are around 12.9 degrees, according to the Indian Meteorological Department.

However, it wasn’t just November: Delhi also experienced its coldest October in 58 years, with an average low temperature of 17.2 degrees Celsius. To find a lower average temperature in October, one will have to travel back in time to 1962, when it was 16.9 degrees Celsius, according to IMD data.

And it will likely get worse, with IMD’s seasonal forecast on Sunday predicting a colder winter (“below-normal minimum temperatures”) in New Delhi and parts of north and northwest India. Monday was the coldest day in Delhi in November with the minimum temperature falling to 6.9 degrees
Celsius.

Kuldeep Srivastava, head of IMD’s regional weather forecast center (RWFC), attributed the colder November to “a combination of factors including global conditions such as La Niña” and local conditions such as “the absence of cloudiness …; whenever there are clear skies, the minimum temperature drops ”.

He added that the minimum temperature will remain between 7 and 8 degrees for the next few days, a degree or two below normal, but that maximum temperatures would be marginally higher than normal.

La Niña is a climate phenomenon that sees cooler ocean temperatures in the Pacific, which has a strong correlation with wetter monsoons and cooler winters in India. It also has a significant correlation with the number and strength of cyclones in the Bay of Bengal. Cyclone Nivar crossed the coast of Tamil Nadu last week, bringing widespread rains to the region and causing some damage. IMD has forecast that another cyclone will cross the coast of Sri Lanka in early December, bringing more rain to Tamil Nadu.

The capital has also experienced four cold waves this month, on November 3, 20, 23 and 24. The last time Delhi saw multiple cold waves during November was in 1964, when three of them occurred. Significantly, the last time Delhi saw a cold snap in November was in 2014. The lowest average minimum temperature of all time in November was recorded in 1930, at 8.9 degrees Celsius.

DS Pai, head of climate research and services at IMD Pune, said that in addition to La Niña and other factors, the absence of western shocks also caused a variation in temperature. He explained that these disturbances, storms that originate in the Mediterranean, usually cause an increase in temperature.

IMD Director General M Mohaptra said that while global factors like La Niña have already taken their toll, this is magnified when local and regional factors also contribute, resulting in extreme weather like the one Delhi has seen. in November.

He also pointed to the dry September that the capital saw this year as another reason. “… it means there was less humidity and the atmosphere was mostly dry, which resulted in clear sky conditions. Clear skies allow for more radiant cooling, which means heat dissipates quickly and makes the night cooler, leading to a drop in minimum temperature. ”

Meanwhile, lower minimum temperatures and a slight reduction in wind speed caused air quality to deteriorate to the “very poor” area on Monday. The average air quality index (AQI) was 318, up from 256 on Sunday. There is bad news on that front too. “Winds will become calm from December 4-5 and air quality may deteriorate further as both the low temperature and the absence of winds will not allow the dispersion of pollutants,” said Srivastava.

Reference site

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