Delhi’s AQI up by nearly 100 points in a day, highest in October in 3 years

The dip was driven by calm surface winds, high humidity and a drop in night temperature, which led to a temperature inversion — a condition where a layer of warm air traps cooler air near the surface, preventing pollutants from dispersing.

Thursday’s maximum temperature was 27 degree Celsius, four notches below normal and the lowest for October in the last two years. The last time a lower maximum temperature for the month was recorded was on October 17, 2023, when the mercury settled at 26.2 degrees Celsius.

The minimum temperature was 20.1 degrees Celsius, four notches above normal.

The IMD said south-easterly winds prevailed over Delhi in the past 24 hours, with speeds up to 10 kmph. The combination of weak winds and low day-night temperatures limited atmospheric mixing and allowed pollutants to accumulate close to the ground.

Visibility reduced sharply across several parts of the city. Around 7.30 am, a visibility of 1,000 m was recorded in Palam and 800 m in Safdarjung. Areas such as Kartavya Path, Burari, Akshardham and Anand Vihar remained shrouded in haze.

The Air Quality Early Warning System said that Delhi’s ventilation index, which indicates the atmosphere’s ability to disperse pollutants, remained below the favourable level of 6,000 sq m per second. A low mixing height and high humidity of around 90% further restricted the vertical spread of pollutants. Data from the Decision Support System showed that while the contribution of stubble burning to Delhi’s PM2.5 levels remained modest at 2.57%, vehicular emissions accounted for nearly 16.7% as of Wednesday.

Anand Vihar and Vivek Vihar recorded “severe” air quality levels, with AQI readings of 408 and 415, respectively. As many as 33 monitoring stations across the city reported “very poor” air quality with readings above 300, CPCB data showed.

The unusually low maximum temperature and weak wind conditions limited pollutant dispersion, as per the IITM. The IITM forecast said, air quality is expected to remain in the “very poor” range over the next few days, with light winds and stable atmospheric conditions likely to continue. The minimum temperature is forecast to dip to around 15 to 17 degrees Celsius by November 5, while the maximum is expected to hover between 29 and 31 degree Celsius.