Farm fires at record low but impact on Delhi air still high | Delhi News – Times of India

NEW DELHI: As per satellite data, stubble-burning incidents this season (Oct-Nov) in Punjab and Haryana were by far the lowest on record. The farm fire count in Punjab was down a steep 70% as compared to last year while Haryana saw a reduction of 42%. But here’s the rub: Data on different pollution sources in Delhi shows that farm fires continued to be a major contributor to the capital’s PM2.5 levels from late Oct to Nov.

How’s that possible? Experts said low stubble burning doesn’t necessarily me an the impact on Delhi’s air quality will be proportionately less. Intrusion of pollution from stubble burning into the capital depends on transport level winds and air ventilation conditions in Delhi.
Met factors adding to stubble woes
If stubble burning counts are less, but north-westerly winds are consistently blowing in Delhi, the stubble burning impact would be more on capital’s air. The impact of paddy residue burning events in other states would be more on Delhi if there is not proper ventilation for dispersion of the pollutants,” said a senior scientist.
From Oct 23 to Nov 23 this year, the contribution of stubble burning was more than 15% on 26 days in Delhi’s PM2.5. Of these 26 days, the share of farm fires was above 20% on 14 days. The season’s highest single-day share in Delhi’s air was seen on Nov 1 (a day after Diwali) at 35.2%, followed by 27.6% on Oct 31 and 26.2% on Nov 22, according to Decision Support System’s data.
Last year, stubble burning mostly impacted Delhi’s air from the last week of Oct to mid-Nov but there was stubble burning intrusion during the entire Nov this year due to meteorological reasons. The impact of crop residue burning was mostly negligible in Oct this year, except for a few days around Oct 23. Last season, the highest single-day share was 35% on Nov 3.
An analysis done by scientists at Indian Institute of Tropical Meteorology (IITM), Pune, stated that paddy residue burning counts decreased in neighbouring states in the winter of 2023 as compared to the previous two years but its impact on Delhi’s air quality was higher than in 2021 and 2022 due to meteorological conditions.

In the winter of 2023 (Oct 22 to Nov 30), the contribution of stubble burning was above 10% in 58% of days, more than 15% in 44% of days and over 20% in 30% of days. In contrast, the contribution of farm fires in Delhi’s air was over 10% for 32% of days each in 2022 and 2021. The impact of farm fires in Delhi’s PM2.5 was above 15% in 30% of days in 2021 and 18% of days in 2022. A similar analysis for the current winter season is underway.
Anumita Roychowdhury, executive director, research and advocacy, Centre for Science and Environment, said, the contribution of farm fire to Delhi’s air quality is variable and is highly influenced by the direction and speed of transport wind. “While it is true that there have been days with significantly high contribution of fires to Delhi’s air quality, there have also been several days when Delhi’s pollution has been in very poor category even with minimal influence of farm fires, indicating high influence of local pollution sources. Farm fires need to be eradicated with significant reductions in other sources to clean up the air in the entire region,” she said.
The model used by DSS to calculate the contribution of stubble burning in Delhi’s air captures fire counts using the Visible Infrared Imaging Radiometer Suite (VIIRS) satellite. The model tracks fire counts in Punjab, Haryana, UP, Rajasthan, Delhi, MP, as well as in Pakistan, and also emissions released by burning of paddy residue. Depending on meteorological conditions, the model calculates the percentage share of stubble burning in Delhi’s PM2.5.
However, the VIIRS satellites overpasses India around 10.30 am and 1.30 pm. Some experts have pointed out that farmers in north-west India could be burning stubble in afternoon hours, after satellites have overpassed the region.