Air quality falls to poor as stubble fires rise again
According to the union government’s air quality forecasting wing, the share of stubble burning to the overall pollution levels increased to 8% from just 3% the previous day.Updated: Nov 19, 2020, 02:27 IST
After remaining in the moderate zone for a day, Delhi’ s air quality plunged to the ‘poor’ category again as the number of stubble fires in neighbouring states more than doubled on Wednesday.
According to the union government’s air quality forecasting wing, the share of stubble burning to the overall pollution levels increased to 8% from just 3% the previous day.
The air quality is likely to remain in the lower end of the ‘poor’ zone and may improve to the higher end of ‘moderate’ over the next two days, the government agencies have forecast.
The average air quality index (AQI) according to the Central Pollution Control Board (CPCB) 4 pm bulletin was 211 in the ‘poor’ zone. Delhi’s AQI has fluctuated between poor and severe and moderate in a matter of five days between November 13 and 17.
From an AQI of 435 on November 15, which is in the severe zone, the air improved to poor (221) on November 16 and moderate (171) on Tuesday.
Rain, good wind speed and low fire counts after Diwali had improved the air quality significantly. An analysis of the AQI data shows that on Tuesday, for the first time since 2017, Delhi experienced a moderate air quality day between November 13 and 17.
The System of Air Quality and Weather Forecasting and Research (SAFAR), the union ministry’s air quality forecasting wing, said the number of stubble fire counts on Wednesday rose to around 427 from 98 the previous day. The contribution of stubble fires to the city’s PM 2.5 levels (ultrafine particulate matter with diameter less than 2.5 micrometres) had peaked to around 40% in October, which came down only after Diwali.
“Stubble burning share in PM 2.5 levels in Delhi’s air is estimated as 8%. AQI is forecast to further deteriorate to the higher end of ‘poor’ to the lower end of the ‘very poor’ category on November 21, as the conductive meteorological environment created after rainfall is gradually retreating,” the SAFAR bulletin stated.
V K Soni, head of the environment monitoring research centre of IMD, said wind speed is likely to remain high over the next two days and no significant deterioration is expected.
“The average wind speed is likely to remain around 12-15 kmph, which will allow continuous dispersion of pollutants. Wind speed is likely to reduce on November 21 when the air quality may plunge to the lower end of the ‘very poor’ zone,” Soni said.
Also, IMD scientists said Delhi will get colder over the coming days with the minimum temperature likely to fall to single digit by November 22. A drop in day and night temperatures is not favourable for the dispersion of pollutants but the wind speed is likely to remain above 10 kmph and keep the air quality in check.
Between November 16 and 18, the minimum temperature has dropped by over 5 degrees. On November 16, night temperature was 16 degrees Celsius. On November 18, the minimum temperature dropped to 10.6 degrees C, two notches below the season’s average. The maximum settled at 25.4 degrees C, two notches below normal.
Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, said that widespread snowfall in Jammu and Kashmir, Himachal Pradesh, and upper reaches of Uttarakhand will lead to a fall in both minimum and maximum temperatures by around 2 to 4 degrees Celsius over northwest India in the coming days.
“Cold winds have started blowing in from the western Himalayas, where snowfall has just happened. We are expecting the minimum temperature to drop to around 9 degrees Celsius in the next couple of days. If wind speed remains good and fire counts remain low, Delhi’s air quality is likely to remain under check,” Srivastava said.