Northwesterlies bring in stubble burning fumes into capital; low temperature, slow winds keep them trapped
Air quality in Delhi returned to ‘severe’ after a brief respite due to several factors. The overall air quality index (AQI) was recorded at 416 around 10 AM, on November 12, 2019, according to the Central Pollution Control Board (CPCB).
Northwesterly wind blew into the national capital region, carrying fume of burning stubble from Haryana and Punjab. The pollutants remained trapped in the city’s atmosphere due to low temperatures and low wind speed.
In the Delhi region, 29 of 37 monitoring stations recorded ‘severe’ air quality.
An AQI between 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’, 301-400 ‘very poor’, and 401-500 ‘severe’. Above 500 is considered ‘severe-plus’ or of ‘emergency’ category.
The concentration of harmful pollutants such as particulate matter (PM) 2.5 and PM 10 in the air rose substantially to 303 microgramme per cubic metre (µg/m3) and 426 µg/m3, respectively — more than four times the prescribed safe standard of 60 µg/m3 and 100 µg/m3 respectively.
No respite was expected for the next two days, forecast SAFAR — System of Air Quality and Weather Forecasting and Research, under Union Ministry of Earth Sciences.
“The effective stubble fire counts estimated by SAFAR-integrated multi-satellite methodology are 1,846 on November 10. Stubble plume intrusion is expected to increase and a decrease in surface wind speed over the Delhi region is forecast for the next two days,” read an analysis on the SAFAR website.
The share of biomass in Delhi's air quality is simulated to be 25 per cent on Wednesday if present fire trend is assumed, it added. The share was 18 per cent on Monday.
A western disturbance was located as a cyclonic circulation over Jammu and Kashmir and adjoining north Pakistan. Under its influence, no rainfall was expected in the Delhi region, but the sky was be partly cloudy with cool temperature during the next two days. That can lower the boundary layer height and accumulation of pollutants near the surface.
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