
Despite poorer air quality in Delhi during Diwali this year, favorable weather patterns, including high wind speeds and warmer temperatures, resulted in the best post-Diwali air quality since 2015 (excluding 2022), with the AQI dropping from previous highs.
- Air Quality Trends: Delhi’s 24-hour AQI during Diwali reached 339, improved from the 358 recorded in 2022 and significantly better than the severe 462 recorded in 2021.
- Air Quality Index (AQI): Established by the government in 2014 under the Swachh Bharat initiative, AQI simplifies the presentation of air quality data. It combines pollutant data (PM2.5, PM10, NO₂, CO, and ozone) into a single index to assess pollution levels.
- Key Pollutants: PM2.5, a fine particulate pollutant, poses severe health risks by penetrating the respiratory system and bloodstream, contributing to conditions like asthma and cardiovascular diseases.
- Effect of Weather on Air Quality: Warmer-than-usual October temperatures in Delhi facilitated better pollution dispersion. Higher inversion layers due to the warmer weather prevented pollutants from being trapped near the surface.
- Role of Wind: Strong westerly winds, reaching speeds up to 15 kmph, helped disperse pollutants, reducing AQI levels post-Diwali despite the festival’s increase in air pollution.
- Policy Response: AQI data informs government measures, such as Delhi’s Graded Response Action Plan (GRAP), which implements restrictions (e.g., on diesel generators and coal use) during poor air quality periods.
Explanation of Relevant Terms:
- Air Quality Index (AQI): Introduced in 2014, AQI consolidates pollutant levels into a single figure, color-coded to indicate air quality, from ‘good’ to ‘severe.’
- Graded Response Action Plan (GRAP): A set of progressively severe measures triggered by increasing air pollution levels, aimed at reducing pollution through restrictions and enforcement mechanisms.
- Temperature Inversion: A weather phenomenon where warmer air above traps cooler air (and pollutants) below, often worsening air quality in winter due to lower inversion heights.
This report highlights the influence of weather patterns on air quality and the government’s strategic response to mitigate pollution during critical periods like Diwali.