The air quality index (AQI) in Delhi and the National Capital Region (NCR) has recently shown a significant deterioration, reaching a severe level. This is the highest level recorded since November 19th, when the AQI reached a concerning 460.
Throughout November 2024, Delhi grappled with severe air pollution for eight days. Among these, two days witnessed hazardous levels of air quality. For the majority of the month, 22 days, the AQI remained in the very poor category.
The first half of December provided a temporary respite with the AQI staying mostly within the moderate range. This improvement can be attributed to a moderate-intensity Western Disturbance that impacted the Western Himalayas in early December. This disturbance brought widespread rainfall across the Northwest plains, effectively dispersing pollutants. Furthermore, moderate westerly winds prevailed throughout the first half of the month, aiding in the ventilation of the atmosphere.
However, a recent shift in weather patterns has led to a resurgence in air pollution. A fresh Western Disturbance is currently approaching the Western Himalayas, inducing a cyclonic circulation over Central Pakistan and Punjab. This has resulted in a decrease in wind speed and a change in wind direction from West to East Delhi, leading to an increase in moisture levels.
The combination of light winds, high moisture, and low temperatures creates ideal conditions for fog formation. Pollutants, including particulate matter (PM2.5 and PM10) and harmful gases, get trapped within this layer of fog, resulting in the formation of smog. The absence of strong winds further hinders the dispersion of these pollutants.
Based on current weather conditions, significant improvement in Delhi's air quality is not expected in the coming days.