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


The peak daily contribution of stubble burning to PM 2.5 levels in Delhi so far this year has been lower compared to previous years, data from the System of Air Quality Forecasting and Research (SAFAR) shows.

The highest contribution from stubble burning to PM 2.5 levels in Delhi on a single day this season was 34% on November 3. The peak single-day contribution last year was higher at 48% on November 7. In the past five years, the highest contribution on a single day was recorded on November 5, 2018 – 58%. This contribution peaked at 44% on October 31, 2019, and 42% on November 5, 2020, according to data provided by Gufran Beig, founder project director, SAFAR. In previous years, the contribution of stubble burning had peaked by the first week of November.

On Saturday, the contribution of stubble burning was 17% in Delhi, a little below the 19% recorded the previous day. This is 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. So far this season, both Punjab and Haryana have recorded a smaller fire counts compared to the same period last year. Punjab has recorded a fire count of 43,144, below the count of 59,121 recorded till November 12 last year. So far this season, Haryana has recorded 2,979 fire events, less than 5,190 recorded till November 12 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 to 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.





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