Peak daily impact of stubble burning on Delhi’s PM 2.5 levels so far is lower than previous years

On Sunday, the contribution of stubble burning was 24%, higher than the 17% recorded on Saturday and 19% recorded on Friday. The AQI on Sunday was 303 in the ‘very poor’ category, and same as the AQI recorded on Saturday, according to the CPCB’s 4 pm bulletin.

The stubble burning contribution has remained on the lower side despite the count from farm fires in Punjab increasing sharply on Friday. Punjab recorded a fire count of 2,467 on Saturday, lower than the 3,916 recorded on Friday, data from the Indian Agricultural Research Institute shows. Sunday’s fire count was also low at 2,175.

So far this season, both Punjab and Haryana have recorded smaller fire counts compared to the same period last year. Punjab has recorded a fire count of 45,319, below the count of 62,863 recorded till November 13 last year. Haryana has recorded 3,111 fire events, less than 5,400 recorded till November 13 last year.

Winds have had much to do with lowering the impact of stubble burning on PM 2.5 levels in Delhi. Despite upper-level winds blowing from the northwest being favourable for the transport of pollutants from stubble burning to Delhi, the local wind speed has helped ensure dispersion of pollutants, according to an update issued by SAFAR on Saturday.

On November 14, the upper-level winds are likely to become weaker, reducing the likelihood of transportation of pollutants from stubble burning and bringing about an improvement in the AQI, the SAFAR forecast indicates.

“Last year’s peak stubble burning contribution coincided with Diwali. The fires were delayed by about 10-15 days this year. If harvesting is yet to be completed now, then the counts will increase or the burning period will extend into the first week of December. So far, although the contribution and fire count have been high, what is coming to Delhi’s rescue is local winds, which are not calm. This means that the pollutants have been getting dispersed quickly. If stagnant conditions persisted, the contribution would have been higher. Local winds are not allowing these pollutants to accumulate,” Beig said.

SAFAR has recorded the contribution of stubble burning to PM 2.5 levels in Delhi from around October 12 onwards this year, but the share remained below 6% till around October 25, and rose to over 20% by October 29. “When you compare this to previous years, the counts were not significant till around October 15 this year. Earlier, it would start increasing from around October 5 onwards,” Beig added.