Delhi’s air quality remains ‘severe’, no immediate respite in sight

The predominant wind direction impacting Delhi’s air over the last three days has been northwesterly -- one which brings stubble smoke towards the national Capital

Delhi’s air remained firmly in the severe category on Friday as calm winds, low temperatures and stubble intrusion continued to impact the national Capital’s air.

With Thursday’s reading of 419, Delhi has now recorded seven severe days this month now. (HT Photo)

Delhi’s 24-hour average air quality index (AQI) at 7am was recorded at 437 (severe) -- a rise from Thursday’s 4pm reading of 419, the Central Pollution Control Board (CPCB) data showed.

This number had gradually risen to 440 (severe) by 10pm on Thursday, before marginally improving in the last few hours, it showed.

Visibility at 7am was 500 metres at Palam. It had dropped to as low as 200 metres on Thursday morning.

The predominant wind direction impacting Delhi’s air over the last three days has been northwesterly -- one which brings stubble smoke towards the national Capital.

This is expected to be easterly post noon today, the IMD has forecast.

Even then, wind speed should largely remain calm through the day, briefly picking up to 5 km/hr between 12pm and 6pm, it said, not giving any significant relief to the capital.

“Delhi did not see a change in wind direction to easterly, as expected on Thursday, and winds also remained calm till almost noon. At Palam, they picked up marginally to 6 km/hr post noon, but at Safdarjung, wind speed was almost nil throughout the day,” said Kuldeep Srivastava, scientist at IMD, stating similar wind speed is expected over the next two days.

“Chances of a change in wind direction are now more likely on Friday,” he added.

CPCB data showed Delhi’s first half of November ended with an average AQI of 376, which was more polluted than last year’s first half of November (345), but less polluted than 2021 (385), 2020 (387) and 2019 (376) as well.

Delhi has largely been helped by the spell of rain it recorded between November 9 and 10, which brought AQI below 300 again and gave Delhi three consecutive and relatively ‘less polluted’ poor air days.

Delhi’s average AQI without any rainfall on those three days hovered around 410.

The data according to Delhi government’s real-time source apportionment on Thursday meanwhile showed that the contribution of biomass burning to Delhi’s PM 2.5 was 28%, while vehicles were contributing 26% on the day. Secondary inorganic aerosols — particles formed in the air as a result of gases reacting with each other from combustion sources — had meanwhile contributed by 35% to PM 2.5 formation, it said.

With Thursday’s reading of 419, Delhi has now recorded seven severe days this month now.

It is on track to record an eighth such day today.

Last November, it only recorded three severe days, but the count was 11 in 2021 and 9 in 2020.

Night-time temperatures meanwhile continues to fall.

Delhi’s minimum was recorded at 11.3°C – two notches below normal. It was 10.9°C on Wednesday, a season-low so far.

Delhi’s maximum was 27.5°C on Thursday, which was a degree below normal.

IMD forecast shows Delhi’s maximum should hover around 28°C today and the minimum should be around 12°C.