Calm winds, local emissions worsen Delhi’s air quality

Delhi also witnessed shallow fog and mist in the early hours, with the minimum temperature recorded at 8.3 degrees Celsius while the maximum temperature was recorded at 25.4 degrees Celsius.

Cold conditions, combined with calm winds, led to a bad air day for Delhi, with the Capital’s air quality index (AQI) recorded at 368 (very poor) on Thursday, as per the daily national bulletin released by the Central Pollution Control Board (CPCB) at 4 pm.

Commuters at Patel Nagar in New Delhi on Thursday. The city’s AQI was recorded at 368 (very poor) on Thursday. (Sanchit Khanna/HT Photo)

The CPCB classifies an AQI between 0-50 as ‘good’, between 51 and 100 as ‘satisfactory’, between 101 and 200 as ‘moderate’, between 201 and 300 as ‘poor’, between 301 and 400 as ‘very poor’ and over 400 as ‘severe’.

Delhi also witnessed shallow fog and mist in the early hours, with the minimum temperature recorded at 8.3 degrees Celsius -- the same as Wednesday -- while the maximum temperature was recorded at 25.4 degrees Celsius, which is around normal for this time of the season.

India Meteorological Department (IMD) officials said Delhi’s minimum temperature is unlikely to dip further in the next few days, with partly cloudy skies and shallow fog keeping the temperature in check – an impact of the western disturbance affecting the northern plains till December 3.

“Owing to the disturbance, there is a slight rise in the minimum temperature, and the same disturbance has also led to a change in wind speed… The moisture content has also increased and this will lead to a drop in the maximum temperature and a slight rise in minimum temperature as heat during the day will not be able to reach the surface completely, while the same heat will take time in escaping at night,” said RK Jenamani, scientist at IMD.

Thursday’s AQI was a slight deterioration from the reading of 365 (very poor) on Wednesday, and forecasts by the Early Warning System (EWS) for Delhi, under the union ministry of earth sciences, show that the Capital’s AQI will inch closer to the ‘severe’ category over the next three days as calm winds continue to cause unfavourable conditions for the dispersion of pollutants.

However, the AQI is not likely to slip into the ‘severe’ category. “The AQI is likely to deteriorate further over the next three days, but will remain in the ‘very poor’ category till December 4, during which time meteorological conditions will be highly unfavourable for dispersion of pollutants. The outlook for the subsequent six days shows that the AQI will largely remain in ‘very poor’,” the EWS forecast said.

Delhi has not seen a severe air day since November 4, when the AQI was 447.