Delhi may breathe better air during October-November

Early withdrawal of monsoon may result in fewer “severe” and “very poor” air quality days over the next two months, according to Central government-run air monitoring agency SAFAR

October 01, 2022 01:44 am | Updated 01:07 pm IST - NEW DELHI:

Heavy smog covered Kartavya Path in Delhi on Friday.

Heavy smog covered Kartavya Path in Delhi on Friday. | Photo Credit: SUSHIL KUMAR VERMA

The central government-run air monitoring agency SAFAR (System of Air Quality and Weather Forecasting and Research) has posited two scenarios for Delhi’s air quality during the upcoming winter season.

Scenario 1: If stubble burning in the neighbouring States peaks by October-end and there are half as many fires as those reported last year, Delhi will likely have no “severe” air pollution days in October and November, according to the air-monitoring agency. However, there will be more “very poor” air days comparatively. 

Scenario 2: If stubble burning peaks around the same time as it did last year (mid-November) and the number of fires remains the same, Delhi will suffer from as many “severe” air pollution days this October-November as it did during this period last year. However, even in this case, the number of “very poor” air quality cases will be fewer.

In other words, even if the stubble burning pattern in neighbouring States is repeated this year, Delhi will still experience an overall better quality air during the next two months.

Three factors

There are three reasons for this — mixing depth, wind speed and timely withdrawal of monsoon.

Mixing depth is the height, measured from the surface of the earth, up to which pollutants can be dispersed into the atmosphere. During winter, the mixing depth decreases, which leads to an increase in the concentration of pollutants.

Gufran Beig, founder and project director, SAFAR, said after the monsoon withdraws, the wind speed tends to reduce, leading to a spike in air pollution. As per the India Meteorological Department (IMD), the monsoon withdrew from Delhi on September 29, earlier than last year.

“As a result of this, the mixing depth won’t be as low as last year. In other words, the combination of mixing depth and slow wind speed won’t be as deadly as it was last year,” Mr. Beig said. An Air Quality Index between 0 and 50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor”, and 401 and 500 “severe”. Severe air pollution “seriously impacts” those with existing diseases, as per Central Pollution Control Board.

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