Delhi recorded the season’s lowest minimum temperature for a second straight day on Monday, and its air quality worsened, though it stayed in the “moderate” category.
Monday afternoon, the weather’s impact on air pollution was mixed. The wind through that layer averaged 17km/h, close to the usual 15km/h. Those figures come from the HT analysis, which pairs the balloon readings with wind estimates from the European Centre for Medium-Range Weather Forecasts. But the balloon itself measured a stronger wind, 20km/h, which would explain why pollution did not spike to higher levels that are typical during this season. The evening brought no relief. Readings varied across the city.
The 24-hour average air quality index ( AQI ) was 174 in the Central Pollution Control Board ’s (CPCB) 4pm bulletin on Monday, up from 153 on Sunday. At 4.30am, a layer of warm air (an inversion) sat about 200 metres above the city, lower than Sunday’s 300 metres, and the air near the ground at Safdarjung was calm overnight. By 4.30pm the sun had mixed the pollution about 1,150 metres up, below the usual 1,750 metres for late October. Safdarjung airfield reported calm air in all five of its reports between 4pm and 9.30pm, and no rain.
As the Capital headed into the new week, the weather held the night’s pollution close to the ground, according to an HT analysis of IMD’s weather-balloon readings from Safdarjung . At 9pm, 13 of the 57 stations reporting an AQI were in the “poor” category, 42 were “moderate” and two were “satisfactory”, according to CPCB data.
