PM2.5 concentration more than doubles to 244 micrograms per cubic metre in 24 hours, while the city’s AQI touches 387 amid stagnant winds and incoming farm-fire smoke.
Delhi’s air quality deteriorated sharply on Thursday, with PM2.5 concentration more than doubling in 24 hours to 244 micrograms per cubic metre by 6pm, around four times the national safe limit. The city’s Air Quality Index (AQI) climbed to 387 by 10pm, placing it in the ‘very poor’ category.
According to Central Pollution Control Board (CPCB) data, the AQI rose from 313 at 2am to 366 by 6pm before reaching 387 at night. As many as 21 of the 58 monitoring stations reporting data recorded ‘severe’ air quality, with readings above 400.
Weather conditions contributed significantly to the deterioration. The height of the atmospheric mixing layer, which allows pollutants to disperse, dropped to around 400 metres on Thursday, from 1,400 metres on Tuesday. Weaker surface winds and high humidity further restricted the dispersal of pollutants.
North-westerly winds, blowing at around 34 kmph at higher altitudes, also carried smoke from crop-residue fires in Punjab and Haryana towards the Capital.
Visibility at Safdarjung fell to 800 metres on Thursday afternoon, compared with 2,500 metres a day earlier.
The India Meteorological Department has forecast no immediate rainfall, with light winds expected over the next three days. Stronger afternoon winds may bring some relief over the weekend.
Sunil Dahiya, founder and lead analyst at Envirocatalysts, said Delhi was facing the combined impact of incoming farm-fire smoke and weather conditions that prevented pollutants from dispersing.
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