Delhi at 323, one station at 414: a warm, windless night does what the farm fires alone could not

Delhi woke on Thursday to an Air Quality Index of 321 at 07:00 local time (02:30 CET), rising to 323 an hour later, according to the Central Pollution Control Board’s hourly data¹. That is in the “very poor” band, which runs from 301 to 400, and eight points above Wednesday’s official daily average of 313¹. The worst station, IIT Delhi, read 414, in the “severe” band^1,2.

Fifty-seven stations, one picture. Of the 57 stations reporting, 39 were “very poor”, 16 “poor”, one “severe” and one “moderate”: the Cantonment, at 128². Fine particles, PM2.5, were the leading pollutant at 48 of them^1,2. After IIT Delhi came NSUT Jaffarpur at 399, ITO at 397 and North Campus at 394².

The weather did the trapping. Calm winds overnight kept pollutants from dispersing, and a layer of warmer air above the ground restricted vertical mixing, the Hindustan Times reports¹. The nights were unusually mild: Safdarjung, the city’s base station, recorded a minimum of 16.5°C, 3°C above normal, and Lodhi Road 16.6°C, 4.6°C above normal¹. No rain fell at any of the five weather stations¹.

The fires are part of it, and harder to count. Punjab recorded 2,347 farm-fire incidents up to 4 November, 17.3% fewer than a year earlier, according to an earlier HT report¹. But burning has shifted later into the day, after the satellite pass at about 13:30, so both counts are undercounts¹. Traffic and other local sources add the rest¹.

What to take from it. This is not a new story, and that is precisely the point: every November the same mix of stubble, traffic and still air arrives, and every November the monitoring network records it station by station, hour by hour. That record is what makes the policy argument possible. Air like this disperses when the wind returns; the dull work of cutting what goes into it has to be done in the other eleven months.