Season-high stubble smoke plunges Delhi air into ‘severe’ again

Increased smoke from stubble burning and unfavourable meteorological conditions over the Capital on Friday and Saturday led to the deterioration of the air quality index to the “severe” category, as pollutants accumulated over the region and winds slowed down. Stubble smoke accounted for 37.51% of Delhi PM2.5 (particulate matter with a diameter of 2.5 microns or less) concentration on Friday, a season-high, according to the Centre’s Decision Support System (DSS).
Delhi recorded a 24-hour average air quality index (AQI) of 417 (“severe”) at 4pm on Saturday, according to the Central Pollution Control Board’s (CPCB’s) daily bulletin. It was 396 (“very poor”) a day before.
Winds, which had become favourable for the dispersion of pollutants, picked up to 14 km/hr during the day on Friday before slowing down towards late evening, predominantly remaining calm. Delhi witnessed a dip in the minimum temperature, to 15.3°C on Saturday from 15.6°C recorded a day before, and instances of firecrackers being burst across the city on Friday night were also reported.
“Meteorological conditions were expected to be favourable on Saturday, increasing to 15km/hr during the day, but winds remained slow. The maximum wind speed was 8km/hr, but it mostly remained calm. We expect winds could pick up to 15km/hr on Sunday, which could again help improve the AQI,” said Mahesh Palawat, vice president at Skymet meteorology.
Palawat said that emissions from the bursting of firecrackers, on the occasion of Gurupurab on Friday, may have also played a role in the deterioration.
As the day progressed, the AQI deteriorated to 426 by 6pm on Saturday, and 438 by 10pm.
On Saturday evening, the Commission for Air Quality Management (CAQM) held a review meeting with state governments in the NCR on the implementation of Stage 3 of the Graded Response Action Plan (Grap). The pollution body asked for augmenting mechanised road sweepers and the shutdown of construction and demolition sites violating the rules.
The review meeting was headed by CAQM member Sujit Kumar Bajpayee, who noted that the rate of resolution of complaints on different social media sites was not satisfactory, and said that agencies must resolve grievances within a week.
Further, the CAQM called for special attention to pollution hot spots in NCR, asking state governments to share reports on the same. “Delhi has already presented their action plan for identified hot spots in the high-level meeting held by the commission on November 8,” a CAQM official said.
NCR cities, despite having better AQI than Delhi, did not fare much better. In Haryana, Gurugram recorded an AQI of 320 (“very poor”) and in Uttar Pradesh, Noida recorded an AQI of 328 (“very poor”), Greater Noida 287 (“poor”) and Ghaziabad 363 (“very poor”).
CPCB classifies AQI between 0 and 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”.
Northwest India has been recording consistent northwesterly-westerly winds since Tuesday, which also brought widespread dense fog to the region on Wednesday.
Moderate fog was once again reported across the Capital on Saturday morning, with visibility dipping to 300 metres at 7.30am. The continued winds also facilitated the transport of stubble smoke to Delhi-NCR, which was 30.8% on Wednesday and 33.33% on Thursday, before reaching a season-high on Friday.
Before this, the highest single-day contribution was reported on November 1 (35.17%), when strong northwesterly winds were blowing towards the region.
Saturday was this winter’s third “severe” air day. Despite not recording “severe” air till November 12, Delhi recorded 14 consecutive “very poor” air days since October 29.
The AQI turned “severe” for the first time this season on November 13, when the AQI was 418, deteriorating further to 424 (“severe”) a day later, resulting in the implementation of Grap Stage 3.
Under Grap Stage 3, there is a ban on BS-3 petrol and BS-4 diesel four-wheelers, private construction and demolition, BS-3 or lower medium goods vehicles in Delhi and interstate buses, unless they run on CNG, are BS-6 or electric.
An official with the India Meteorological Department (IMD) said moderate fog prevailed in the early hours of the day, when winds were calm. “The lowest visibility was 300 metres at 7.30am at the Safdarjung observatory and 500 metres at the Palam observatory at 7 am. Mainly smog conditions prevailed in the city and wind speed was less than 6km/hr through the day,” the official said, forecasting winds of up to 18km/hr during the day.
The season-low minimum temperature of 15.3°C was still above the normal, by two degrees. The maximum temperature, meanwhile, was 29.6°C on Saturday, which was one degree above the normal, and down from 30.5°C recorded a day earlier.