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At 6.3 degrees, Sunday morning in Delhi was coldest this December but air turns foul

According to Met officials, the record chill on Sunday was because of a clear sky and wind direction from the northwest.

delhi Updated: Dec 25, 2017 10:46 IST
HT Correspondent
HT Correspondent
Hindustan Times
delhi,delhi weather,air quality
A cold wave has gripped the Capital on the eve of Christmas.(Sonu Mehta/HT PHOTO)

Sunday was the coldest day this December so far with the minimum temperature hitting a low of 6.3 degrees Celsius.

“This was two notches below average and the lowest yet this month. The previous lowest in December 2017 was on the 15th with the minimum recording 7.3 degrees Celsius, while the mercury dipped to 7.4 degrees Celsius on December 10,” a Met official said. “The maximum temperature on Sunday stayed at 25.1, four degrees above what is normal this time of the month,” the official added.

According to Met officials, the record chill on Sunday was because of a clear sky and wind direction from the northwest. “The clouding has cleared away and the clear sky is the reason why minimum temperature witnessed a drop on Sunday. In the days to come, too, the minimum temperature will remain in 6-7 degrees range,” the official said. He added that northern winds are required to get the temperature further down.

Earlier in the day, due to fog, at least 17 trains were cancelled, 19 arrived late and six were rescheduled after a blanket of fog engulfed Delhi on Saturday morning.

Air ‘very poor’ again

In terms of pollution, Delhi saw a “very poor” day with the Air Quality Index (AQI) touching 305. On Saturday, it was 228 in “poor” levels, while on Friday it was 336.

The AQI is calculated on a scale of 0-500. An AQI between 0-50 is considered good, 51-100 satisfactory, 101-200 moderate, 201-300 poor, 301-400 very poor and 401-500 is severe.

The levels of PM10 and PM2.5 saw substantial increase throughout the day as well. While PM10 concentration went up from 253.2μg/m3 at 6am to 314.9μg/m3 at 6pm, the level of PM2.5 saw increase from 141.4.8μg/m3 at 6am to 186μg/m3 at 6pm.

Both PM10 and PM2.5 are ultrafine particles, the dominant pollutants in Delhi. The acceptable levels of PM10, the larger particulate matter, and PM 2.5, which measures the finer and more dangerous particulate matter, are 100μg/m3 and 60μg/m3, respectively.

Met officials said this dip in air quality was because of low wind speed. “The wind speed has deteriorated on Sunday and is 7-8km/hour. Tomorrow, it will be around 10-12km/hour and thereby the air will be cleaner,” Kuldeep Srivastava, a senior Met department scientist, said.

On Monday, clear sky is expected with shallow fog in the morning hours. The maximum and minimum temperatures are expected to be around 24 and 7 degree Celsius.

“Shallow fog will be there with visibility expected to be around 500m till 8-9 in the morning. However, heavy fog is expected on the night of the 27th and the morning of the 28th. Wind direction will change and speed will decrease. The current westerly and north westerly winds will become easterly and south easterly,” Srivastava said.

First Published: Dec 24, 2017 20:43 IST