Delhi’s air back in ‘severe’ zone as smoke, slow winds trap pollutants

The surge in pollution follows an upswing in the number of stubble fires in upwind Punjab over the past few days.

Delhi’s air quality index (AQI) dropped into the deep red “severe” zone yet again on Wednesday, primarily due to the heavy influx of smoke from stubble fires, which was worsened by slow winds, dipping temperatures and remnants of firecracker emissions, ensuring that the city’s pollution crisis persists and residents remain trapped in a hazy mist.

Residents of Delhi-NCR have started wearing masks to protect themselves from pollution and smog in the morning, in Noida on Wednesday. (Sunil Ghosh/HT Photo)

The Capital’s AQI on Wednesday clocked 401, according to the Central Pollution Control Board’s (CPCB) 4pm bulletin, marginally worse than 397 (very poor) a day ago, and the first severe reading since November 9.

The surge in pollution follows an upswing in the number of stubble fires in upwind Punjab over the past few days. Satellite data recorded 2,544 farm fires across the state on Wednesday, significantly more than 1,776 a day ago, and 1,624 on Monday.

Northwesterly winds, blowing into Delhi from Punjab, have over the past few days carried plumes of smoke from these burning paddy fields and settled these pollutants in the Capital’s air, capping the city’s turnaround after two-and-a-half days of relatively clean air.

A sharp spell of rain last Thursday night and Friday morning wiped Delhi’s air of pollution and dragged it out of a spell of seven days of severe air in nine days. The air quality improved till Sunday (Diwali day) afternoon, when the AQI settled at 218.

But it went downhill from there. Residents across Delhi set off firecrackers all evening, violating the Supreme Court’s directives and giving the city hazardous pollution levels once again. AQI, as a result, spiked 140 points to 358 at 4pm on Monday. By 10pm on the same day, AQI surged to 403.

Meanwhile, the winter chill continued to set in on Wednesday, when the minimum temperature dropped to 10.9°C, the lowest yet this season.

Lower temperatures keep the ground surface cool, and prevent pollutants from dispersing.

Weather experts said conditions will remain similar for the next few days. According to the India Meteorological Department (IMD), the minimum and maximum temperatures will continue to be around 11°C and 27°C for the next few days, with a shallow fog in the morning.

However, the weather agency also added that winds picked up speed on Wednesday and that their direction may change on Thursday.

“The wind speed improved from Wednesday and we hope that it will continue to be 6-8 kilometres per hour for the next few days. We are also expecting easterly winds from Thursday,” said Kuldeep Srivastava, scientist at IMD.

According to the forecast by CPCB, Delhi’s AQI is expected to be in the ‘very poor’ category over the next six days.

“The air quality is likely to remain in the ‘very poor’ category from November 16 to 18 and may stay in the same zone for the subsequent six days. The predominant surface wind is likely to be calm in the morning,” said the AQI forecast.

Meanwhile, other NCR cities fared marginally better. AQI was 378 in Ghaziabad, 338 in Greater Noida and 360 in Noida on Wednesday. Gurugram had an AQI of 297 in the “poor” zone.

Depending on how weather factors and pollution levels pan out over the next three days, the Delhi government said it will take a final decision on the proposed odd-even traffic rationing scheme and inducing artificial rain over the city.

“We have been informed by experts that over the next three days, the temperature and wind speed may not change much. So, pollutants will be trapped and pollution levels will continue to be high. We are continuously monitoring the situation. Depending on the condition over the next three days, we will take a definite call on the odd-even scheme and the plans for artificial rain,” said Delhi environment minister Gopal Rai.