Delhi achieves second lowest air pollution levels after Diwali since 2015. Here's the reason
Strong, sustained winds swept through Delhi, rapidly dispersing dense smoke layer and bringing AQI down to 339 by 4pm Friday, further improving to 323 by 7pm.
Delhi's air quality has been the second cleanest post-Diwali since 2015, maintaining a “very poor” Air Quality Index (AQI) instead of deteriorating to “severe". This stability is attributed to "strong wind ventilation", with speeds reaching 16 kilometers per hour.
While the 24-hour air quality index (AQI) climbed steadily through Thursday night — from 328 in the early evening to 338 at midnight, reaching 362 by 9am Friday — the city experienced an unexpected respite. Powerful, continuous winds swept across Delhi, quickly dispersing the thick layer of smoke and lowering the AQI to 339 by 4pm on Friday, further dropping to 323 by 7pm.
The use of fireworks, an increase in stubble burning, and emissions from various local sources that release harmful gases elevated the city's air quality to the higher end of the "very poor" range late Thursday night and into Friday morning. Mahesh Palawat, vice president at Skymet meteorology, elucidated the intricate relationship between temperature and pollution: "Higher temperatures maintain a high mixing height, allowing pollutants to move and disperse freely." Cold temperature decreases wind speed and causes pollutants to be trapped near the ground due to a process known as inversion.
During winter, the mixing height usually decreases to 200-300 meters, but on Thursday it remained at 2,100 meters. Despite poor air quality on Diwali, reaching severe levels at midnight, conditions improved rapidly the following day and reached moderate levels by afternoon. This occurs due to warm temperatures, moderate wind, and natural airflow. The intense tranquil winter inversion conditions have not arrived yet. Nevertheless, October has experienced a higher number of days with poor and very poor air quality compared to previous years.
Despite farm fires contributing only 1-3%, local and regional pollution has had a significant impact on air quality during this month," Anumita Roychowdhury, executive director of Research and Advocacy at the Centre for Science and Environment (CSE) stated.
