Delhi pollution: AQI improves to enter very poor zone

Delhi’s air quality improved marginally to reach the ‘very poor’ category on Wednesday as the capital recorded an overall air quality index (AQI) of 372 – a drop from Tuesday’s 404, data from the Central Pollution Control Board (CPCB) showed.

According to experts, though local meteorological conditions largely remained the same, a slight drop in the speed of wind that is bringing stubble emissions to Delhi has led to this slight improvement in the last 24 hours. Forecasts on Wednesday showed transport-level winds will once again pick up from Thursday onwards, with two days of ‘severe’ air a possibility once again.

According to the System of Air Quality and Weather Forecasting And Research (Safar), winds that transport stubble emissions from Punjab and Haryana to Delhi, are expected to pick up again over the next two days. This likely to deteriorate over the next two days.

Though the number of farm fire incidents went up to 5,317 on Wednesday from 3,476 on Tuesday, their share in the overall pollution mix of Delhi stayed at 27%.

Gufran Beig, founder and project director at Safar, says a combination of strong transport-level winds, along with calm wind speed over Delhi is likely to see ‘severe’ air again. “If the farm fires remain the same, the share of stubble burning will start increasing again from Thursday as winds from Punjab and Haryana will pick up speed. Meanwhile, Delhi will see calm wind conditions, which will help trap pollutants over the city,” he said.

In an analysis done by the Centre for Science and Environment (CSE) on Wednesday, the body said this smog episode is expected to last another two days, with it already matching the first smog episodes of 2018 and 2020 – each of which lasted six days.

“While very high concentrations of PM2.5 have hogged attention, the levels of gases – ozone, CO or NO2 -- have also remained elevated during this smog episode,” says Avikal Somvanshi, programme manager, Urban Lab, CSE, adding that if conditions do not improve, this smog episode is likely to overtake the 2019 smog episode, which lasted eight days.

Delhi recorded a minimum temperature of 13.4 degrees Celsius on Wednesday, the lowest so far this season. It was 13.5 degrees on Tuesday.

“A gradual drop in minimum temperature is expected over the next seven days, touching 11 degrees Celsius by November 16,” a met official said.