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Delhi's air quality took a sharp downturn on Sunday, reaching its worst level in nearly 10 months as calm winds and low temperatures hindered the dispersion of pollutants. The Air Quality Index (AQI) soared from 316 on Saturday to 382, placing it firmly in the higher end of the 'very poor' category. This marked the highest AQI since January 31st, when it reached 392. The city's air quality is predicted to remain within the 'very poor' category until Wednesday.
Experts attribute the worsening air quality to a shift in wind direction from north-westerly to south-easterly on Sunday. The wind speed dropped to zero during this transition phase, exacerbating the accumulation of pollutants. The nighttime temperature, which was typically 3-4 degrees above normal in October, has begun to dip in November. On Sunday, the city recorded its lowest minimum temperature of the season at 16.5 degrees Celsius, one degree above normal. This represents a four-degree drop from the minimum temperature on October 31st.
The calm winds and low temperatures have created a perfect storm for air pollution in Delhi. As the wind direction shifted to south-easterly, the winds became calm during the daytime, further exacerbating the situation. While the AQI was 366 at 8 am on Sunday, it surged to 382 by 4 pm. Data from the Central Pollution Control Board (CPCB) revealed that 14 out of 40 monitoring stations recorded an AQI exceeding 400, placing them in the 'severe' category. Anand Vihar, the most polluted area, recorded an AQI of 436, followed by Nehru Nagar at 430 and Punjabi Bagh at 425.
The Air Quality Early Warning System for Delhi (EWS) issued a warning on Sunday, stating that meteorological conditions were 'extremely unfavourable' for pollutant dispersion. They predict the air quality to remain in the 'very poor' category until Wednesday, with a forecast of 'very poor' to 'severe' for the following six days, starting November 6th. While the share of stubble burning in Delhi's PM2.5 levels was 14.96% on Saturday, the contribution from this source is expected to decrease as south-easterly winds prevail. Satellite data from the Indian Agricultural Research Institute revealed 351 residue burning events on Sunday, with the majority (216) occurring in Punjab, followed by Haryana (19), Uttar Pradesh (16), Rajasthan (36), and Madhya Pradesh (67).