Delhi’s air quality remains ‘severe’; mercury plunges to 12.3°C
A 24-hour average Air Quality Index (AQI) of 488 (severe) was recorded at 8am compared to 494 at 4pm on Monday, the joint-second highest ever in the Capital
Delhi’s air quality remained at the higher end of the “severe” category on Tuesday even as visibility improved marginally in parts of the city amid a sharp dip in the minimum temperature, which fell to the season’s low of 12.3°C.
A 24-hour average Air Quality Index (AQI) of 488 (severe) was recorded at 8am compared to 494 at 4pm on Monday, the joint-second highest ever in the Capital. Delhi recorded the same average AQI on November 3, 2019. The all-time high was on November 6, 2016.
No significant improvement was expected. The AQI was likely to remain in a “severe” zone until at least Thursday.
On Monday, the AQI at 15 of the city’s 36 monitoring stations hit 500 at 4pm. Delhi’s hourly average concentration of PM2.5 (a microscopic pollutant with a diameter between 1 and 2.5 micron) on Monday touched a peak of 820 micrograms per cubic metre (µg/m3) at 12pm. It was around 14 times the national 24-hour standard of 60µg/m3 and 164 times the World Health Organization’s daily limit of 5µg/m3.
Smoke from farm fires in Punjab, which remained locked in place by slow winds and plunging temperatures, worsened the air quality. The smog prompted work from home orders while schools and colleges shifted to online mode.
Monday’s AQI was calculated based on 36 stations, all of which were deep in the “severe” range. Throughout the day, at least 15 stations touched 500. There were only nine stations in 2016 when its record AQI was logged.
On Tuesday, 31 of 32 stations recorded “severe” air quality. ITO (396) logged “very poor” AQI. Two north Delhi stations—Narela and Alipur—recorded 500.
A drop in temperature impacts air quality negatively, slowing down the dispersion of pollutants. Delhi’s minimum of 12.3°C is around normal for this time of the year. Before this, the lowest minimum this season was 15.3°C on November 16. Delhi’s minimum temperature has been above normal for over a month since October 17.
The visibility improved in comparison to Monday. Fog coverage over northwest India thinned marginally. “The fog coverage over Haryana, Delhi, east Punjab, and western Uttar Pradesh on Monday has constricted to just western Uttar Pradesh, resulting in improved visibility conditions. Palam reported a minimum visibility of 600 metres, which improved to 900 metres by 8am. Winds of around 7 km per hour were also reported. At Safdarjung, the minimum visibility was 150 metres but it improved to 400 metres by 8 am,” said an India Metrological Department official.
No diversions or cancellations were reported at Delhi’s Indira Gandhi International Airport. Over 10 flights were delayed. The Northern Railways said at least 22 trains were running late due to fog.
The smog dipped visibility to 100m in some parts on Monday, hitting flight and rail operations. At least 11 diversions and over 350 delays were reported at the airport. At least 28 trains to or from Delhi were delayed by over an hour.
Delhi’s baseline pollution was already high due to sources like construction, industries, high transport emissions, and waste burning. Unfavourable conditions and stubble burning exacerbate the situation.
Haryana recorded 36 farm fires on Monday, Rajasthan 152, Uttar Pradesh 133, Madhya Pradesh 639, and Punjab 1,251. The deterioration in the last few days was mainly due to stubble emissions from Punjab and Haryana. The contribution of stubble burning has been over 20% since November 14.
