Delhi’s air back in ‘severe’ zone, rain ahead could bring down AQI

Sunday’s pollution was down to local emissions, which calm winds and low temperatures did little to disperse.

Delhi’s air quality index (AQI) tipped back into the “severe” zone on Sunday evening, after skirting around that level for the nearly two days, as the Capital remained in the chokehold of a poisonous haze once more this month.

A hazy morning at Kartavya Path on Sunday. (Arvind Yadav/HT Photo)

The city registered an average 24-hour AQI of 396 at 4pm, according to the Central Pollution Control Board’s (CPCB) official bulletin. Even as this number itself was worse than 389 a day ago, the reading inched into severe territory — the most polluted of the AQI — at 9pm, with a reading of 401, according to the agency’s Sameer air quality app. By 11pm, this number touched 403.

Sunday’s pollution was, once again, down to local emissions, which calm winds and low temperatures did little to disperse. Indeed, Delhi’s pollution levels picked up despite smoke from farm fires in Punjab not impacting the city’s air.

Some parts of the Capital may receive some rain on Monday, the India Meteorological Department (IMD) forecast on Sunday, though its impact on air quality is only likely to be negligible, with a “very poor” AQI likely.

An AQI between 301 and 400 is considered “very poor”, while a number between 401 and 500 is “severe”. CPCB’s AQI scale maxes out at 500.

Still, Delhi’s long stretch of polluted air this month is likely to render it the dirtiest November since at least 2015 — the year CPCB adopted the AQI system to track air quality.

Till Sunday, Delhi’s monthly average AQI (according to the official 4pm bulletins) stood at 377, the highest for November in the last eight years, show CPCB data. The average AQI was 376 in November 2021 and 374 in November 2016.

Data shows Delhi has recorded nine ‘severe’ air days so far this month, behind only November 2016 (10 severe days) and November 2021 (11 severe days). However, like Sunday, Delhi has also recorded seven days when the AQI has been between 390 and 400 — on the brink of severe.

Hence, the city’s AQI has been 390 or worse on 16 days this month, the most eight years, well past 13 in November 2021.

Kuldeep Srivastava, scientist at IMD said Monday may bring rain thanks to a western disturbance that brought showers to parts of Gujarat and Rajasthan on Sunday.

“The wind speed will also pick up and touch around 15 km/hr during the day,” he said.

Strong winds aid in dispersal of pollutants. Rain also helps settle pollutants, making Monday a favourable day for a slight reduction in pollution. Srivastava said the wind direction was predominantly easterly on Sunday and will remain so on Monday.

“Cold northwesterly winds will return from Tuesday again then and this will once again lead to a drop in minimum temperature.” he added.

Delhi’s minimum temperature was 10.4°C on Sunday — a degree below normal. It was 10.2°C a day earlier. The maximum, meanwhile, stood at 26.4°C, which is around normal for this time of the year. It was 27°C on Saturday.

IMD forecasts show the rain on Monday will lead to the maximum dipping to 22°C, while the minimum should hover around 12°C . On Tuesday, Delhi’s minimum will be around 10°C, with the maximum around 24°C.