With pollutants pushed out by strong winds and rain over the past couple of days, Delhi’s air quality improved further to the ‘satisfactory’ range Friday for the first time in over a month.
The city’s average air quality index (AQI) was 84 Friday. The AQI last reached ‘satisfactory’ levels on October 5, when it was 98, as per the Central Pollution Control Board (CPCB).
Kuldeep Srivastava, scientist at the India Meteorological Department, said winds have been strong over the past few days, peaking at 35 kmph Thursday.
“Air quality has been improving over the past few days, and as a result, concentration of pollutants is already in the lower end… The air quality had improved a lot on Thursday because of strong winds, rain and hail brought on by a passing Western Disturbance in parts of Haryana and Uttar Pradesh. Even though wind speed dropped Friday, it was enough to keep pushing pollutants out,” Srivastava said.
A Western Disturbance is an extratropical storm originating in the Mediterranean region that brings sudden rain during non-monsoon months to northwest India. Scattered rains and hail had lashed parts of Delhi-NCR on Wednesday and Thursday and the AQI in the region reached ‘moderate’ category.
On Friday, parts of the NCR also recorded ‘satisfactory’ air quality, with Gurgaon and Ghaziabad seeing an AQI of 84, and Noida recording 83. Clear sky and sunlight over the region Friday also helped with dispersion of pollutants, which are otherwise trapped closer to the surface on days with low wind speed and less sunlight, Srivastava said.
According to CPCB, the average concentration of PM2.5 and PM10 — fine particles suspended in the air — in Delhi-NCR was 45.2 and 84.6 respectively between noon Thursday and 8pm Friday, which is below the 24-hour acceptable standards of 60 and 100 micrograms per cubic metre air.
The Delhi Pollution Control Committee’s air monitoring stations in Delhi also recorded a fall in real-time concentration of particulate matter in the city. The lowest reading of PM2.5 at Mandir Marg monitoring station was 19 at 7 pm, and at Anand Vihar it was 22 at 3 am.
However, the relief may be short-lived for the city as the Centre-run System of Air Quality and Weather Forecasting and Research (SAFAR) has forecast a deterioration to ‘poor’ air quality Saturday.
Impact of stubble burning in nearby states on Delhi’s PM2.5 levels was estimated to be 5% Friday and is expected to go up to 6% Saturday, according to SAFAR.