Delhi’s air quality deteriorates to higher end of very poor as wind speed drops

New Delhi: Delhi’s air quality deteriorated to the higher end of the ‘very poor’ category on Sunday, with calm winds seen across the city, leading to local pollutants accumulating in the air. The average air quality index (AQI) stood at 369 (very poor) at 9am on Sunday — a deterioration of over 50 points from Saturday’s 4pm reading of 316 (very poor).
Delhi’s AQI on Diwali day on Thursday was 328 (very poor), with this rising marginally to 339 (very poor) the next day at 4pm, when the Central Pollution Control Board (CPCB) releases its daily national bulletin.
Aided by strong winds of 10-15 km/hr, firecracker emissions released on both days were swiftly dispersed, with the AQI even improving to poor briefly on Saturday morning, before it began to deteriorate once more as wind speeds dropped. CPCB classifies AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.
“With winds transitioning from northwesterly to easterly, they became almost calm in the second half of Saturday. The same condition prevailed in the early hours of Sunday but is likely to pick up during the day on Sunday again, likely oscillating between 5-10 km/hr,” said an India Meteorological Department (IMD) official.
Forecasts by the Centre’s Early Warning System for Delhi (EWS) show further deterioration is unlikely with air quality expected to remain in the ‘very poor’ category.
“Delhi’s air quality is likely to be in the very poor category from Sunday till Tuesday,” said EWS.
Despite a change in wind direction, mercury fell lower in the city. Delhi recorded a minimum temperature of 16.5°C on Sunday, which is one degree above normal, but the lowest minimum so far this season. It was 17.1°C a day earlier.