Why was post-Diwali air quality better this year?

Wind speed, warmer temperatures helped disperse pollutants 

By DTE Staff
Published: Friday 28 October 2022

The air quality in the National Capital Region worsened on Diwali as citizens defied cracker bans and stubble-burning incidents increased. Even before October 24, 2022, winds had slowed down and local emissions had begun to accumulate, steadily driving up pollution levels.

Delhi’s air quality was expected to remain in the ‘very poor’ category of the Central Pollution Control Board’s Air Quality Index (AQI) until October 26, 2022, according to weather forecasting agency  System of Air Quality and Weather Forecasting and Research (SAFAR).

However, post-Diwali AQI has improved since 2015 (303 on October 25). It was 462 last year, in the ‘severe’ category. The wind speed from the westerly-southwesterly direction this year has prevented too many pollutants from accumulating in the air and helped disperse some pollution from stubble burning.

Read more: Delhites, all that rain does not mean you will have a smog-free Diwali. Here is why

On October 23, 1,400 fire counts were reported and 1,484 fires on October 24, according to Indian Agricultural Research Institute. Wind speeds increased to 15-20kmph on October 25 during the day, with visibility improving in several parts of Delhi.

Additionally, warmer temperatures during Diwali this time have also prevented the boundary layer (the lowest part of the troposphere) from becoming thinner, allowing the particulate matter to disperse quickly. The boundary layer is where the particulate matter gets trapped.

There have been 5,798 crop residue-burning events recorded in Punjab from September 15 to October 25, as compared to 6,134 last year. Unseasonal rains in October have pushed the dense stubble-burning period to November, leading to slightly fewer farm fires.

Stubble burning contributed 10 per cent to the pollution on Diwali and 5-6 per cent on October 25 as compared to 36 per cent on Diwali last year.

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