Delhi's October Air Quality Best in Past Four Years, Thanks to Good Rainfall

Delhi's air has been cleaner throughout the month of October than it has been since 2018. Last month the average air quality index was 173, whereas in October 2020, the figure was 265, in 2019, the equivalent figure was 233, whereas the average AQI in October 2018 was 268. 

This, according to experts, is due to the monsoon's unprecedented rainfall. This year's delayed monsoon, along with the presence of a western disturbance, resulted in rainfall in Delhi in October. 

According to the Central Pollution Control Board's (CPCB) bulletins, there were no AQI days in Delhi in October this year that were classified as "extremely bad" or "severe".   This is in comparison, to nine 'very poor' air days in 2020, five such days in 2019, and nine in 2018. In October of this year, there were two 'severe' AQI days, compared to one such day in 2018. 

On October 18, when the AQI was 46, Delhi saw its first 'excellent' air day of the year. Since at least 2018, the month of October has never recorded a 'good' air day. 

Three days of 'satisfactory' AQI were registered in October this year, however no such days were recorded in October 2020 and 2018. 

There are active fire events in Punjab and Haryana. 

After falling around October 24 and 25, when areas of northwest India received rainfall due to a western disturbance, active fire incidents in Punjab and Haryana appear to have started up in the last few days. 

According to scientists affiliated with the System of Air Quality and Weather Forecasting and Research (SAFAR) forecasting system, the contribution of crop residue burning to PM 2.5 levels in Delhi has lately reduced since wind direction has not been favourable for pollution transmission. 

According to a CPCB report released on October 30, the active fire count in Punjab on October 29 was 1,353. From at least October 16 onwards, this is the largest active fire count for a single day. 

Since October 26, the number of active fires in Punjab has increased. On October 25, there were 76 fire occurrences, 329 on October 26, and 279 on October 27.

On October 28, the figure surged to 761, and on October 29, it surpassed 1,000. On October 22, when 1,111 fire events were reported, it was the last time active fire counts exceeded a thousand. 

On October 29, there were 161 active fires in Haryana, up from 134 on October 28 and 93 on October 27. 

On Sunday, the air quality in Delhi remained in the 'poor' category for the fifth day in a row, with an AQI of 289. On Sunday, the contribution of stubble burning to PM 2.5 levels in Delhi was 8%, down from 12% on October 30 and over 20% on October 29. 

The minimal contribution of stubble burning to pollution in Delhi can be explained by the recent shift in wind direction.

On November 1 and 2, the wind direction in Delhi is expected to be from the southeast, according to the Air Quality Early Warning System. Pollutants from burning are frequently carried in by winds from the northwest or west.