Several parts of the national capital were engulfed in a dense layer of fog on Saturday morning, which reduced visibility to 100 metres.
New Delhi,UPDATED: 25 Dec 2022 04:19 IST
The mercury dropped to 4 degrees Celsius, four notches below normal, at Ridge weather station, making it the coldest place in the capital.
Courtesy of Press Trust of India: A dense layer of fog engulfed parts of the nation’s capital on Saturday morning reducing visibility to 100 metres, affecting road and rail traffic, while the Ridge area recorded a cold wave.
The Safdarjung Observatory, the main weather station in the national capital, recorded the minimum temperature at 5.4 degrees Celsius, three notches below normal, according to the India Meteorological Department (IMD).
The mercury dropped to 4 degrees, four notches below normal, at Ridge weather station, making it the coldest place in the capital.
Aynagar recorded a minimum temperature of 4.4 degrees and Mungeshpur 4.1 degrees Celsius. The foggy weather delayed 14 trains from 1:30 to 3:30, railway officials said.
At 5.30 am, visibility was 100 meters at Palam and 200 meters at Safdarganj, the two weather stations in Delhi. Among other cities, it had 25 meters in Patiala (Punjab) and Ganganagar (Rajasthan), and 50 meters in Churu.
IMD officials said a layer of fog is mainly seen over Punjab, north Rajasthan, Haryana and Delhi. Another layer is visible in parts of Bihar, while parts of Uttar Pradesh are free from the fog cover, they said.
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According to the IMD, fog is “very dense” when the visibility is between 0 and 50 meters, 51 and 200 “dense”, 201 and 500 “moderate” and 501 and 1,000 when it is “slight”.
The Air Quality Index (AQI) in the national capital was 364 at 9 am, the Central Pollution Control Board (CPCB) said.
An AQI of zero to 50 is considered “good,” 51 to 100 “satisfactory,” 101 to 200 “moderate,” 201 to 300 “poor,” 301 to 400 “very poor,” and 401 to 500 “severe.”
In the plains, the IMD declares a cold wave if the minimum temperature drops to 4 degrees Celsius. A cold wave is also expected when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches below normal.
A “severe” cold wave occurs when the minimum temperature drops to two degrees Celsius or when the deviation from normal is more than 6.4 degrees Celsius.
When the minimum temperature is less than or equal to 10 degrees Celsius and the maximum temperature is at least 4.5 degrees Celsius below normal, it is said to be a ‘cold day’.
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