New Delhi, Dec 24 (PTI) A dense layer of fog engulfed parts of the national capital Saturday morning reducing visibility to 100 metres, and affecting road and rail traffic, while the Ridge area recorded a cold wave.
The Safdarjung Observatory, the national capital’s primary weather station, 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 Celsius, four notches below normal, at the Ridge weather station, making it the coldest place in the capital.
Aynagar recorded a minimum temperature of 4.4 degrees Celsius and Mungeshpur 4.1 degrees Celsius. Foggy weather delayed 14 trains by 1.30 to 3.30 hours, railway officials said.
At 5:30 am, visibility was 100 metres at Palam and 200 metres at Safdarganj, two Delhi weather stations. Among other cities, it was 25 metres at Patiala (Punjab) and Ganganagar (Rajasthan), and 50 metres at Churu.
IMD officials said a layer of fog was seen mainly over Punjab, north Rajasthan, Haryana and Delhi. Another layer is seen over some parts of Bihar, while regions in Uttar Pradesh are free from the fog cover, they said.
According to the IMD, ‘very dense’ fog is when visibility is between 0 and 50 metres, 51 and 200 is ‘dense’, 201 and 500 ‘moderate’, and 501 and 1,000 ‘shallow’.
The Air Quality Index (AQI) of the national capital stood at 364 at 9 am, the Central Pollution Control Board (CPCB) said.
An AQI between zero and 50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor” and 401 and 500 “severe”.
In the plains, the IMD declares a cold wave if the minimum temperature dips 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 is when the minimum temperature dips to two degrees Celsius or the departure 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 the normal, it is said to be a ‘cold day’. PTI NIT GVS NB
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