A drop in temperature slows the movement of pollutants and brings smoke from the fields of Punjab and Haryana, where there have been farm fires recently.
Delhi’s air quality
After five days of temperatures above 20°C (19.4°C), Delhi’s air quality fell to the bad category on Thursday, while the minimum temperature dropped to 16.4°C, the lowest so far this season.
At 9 a.m., the Central Pollution Control Board reported that the hourly air quality index (AQI), which measures air quality, was at the lower end of the poor range at 204. The average 24-hour AQI on Wednesday was 193, which is in the upper range of the moderate category.
An AQI of 0 to 50 is considered to be good, 101 to 200 to be satisfactory, 201 to 300 to be poor, 301 to 400 to be very poor, and 400 and higher to be severe.
At 8 a.m. on Wednesday, the AQI was 196 (moderate), up from 180 (moderate) the previous day. The air quality was probably going to remain poor until Friday due to the change in wind direction to northwesterly and a decrease in local wind speed.
Air quality is negatively impacted by cold northwesterly winds. A drop in temperature slows the movement of pollutants and brings smoke from the fields of Punjab and Haryana, where there have been farm fires recently.
When it was 18.6°C last week, the minimum temperature became the first to fall below 20°C. Following a shift in wind direction, Saturday’s minimum temperature increased to 20.9°C. It increased to 23.1°C on Sunday and 24.4°C on Monday. Tuesday’s minimum temperature in Delhi was 22.7°C, two degrees above average.
On Wednesday, the minimum temperature was two degrees below average and the high was 35°C, one degree above average. This season’s previous low point (18.3°C) was observed on October 3.
The air quality was predicted to stay at the lower end of the poor category through Friday by the Air Quality Early Warning System (AQEWS). The air quality was predicted to be between poor and moderate for the six days after that.
The Union Earth Sciences Ministry oversees the forecasting system known as AQEWS. To prevent pollution, the Commission for Air Quality Management (CAQM) relies on AQEWS.
The AQI was 212 on Friday of last week, the first day of the winter season when Delhi had poor air quality. The Graded Response Action Plan stage-I measures were activated by CAQM on the same day. The solutions include reducing road traffic, occasional mechanized sweeping, watering of the roads, closing down buildings and demolition sites larger than 500 square meters that are not registered with the government, etc.
The air quality index (AQI) decreased to 216 (bad) on Saturday before rising to the moderate range.
According to the CAQM, Delhi only experienced 200 days with good to moderate air quality this year, the second time since 2015. Only once else in the previous eight years has this occurred, and that was in 2020 when lockdowns were necessary due to the Covid-19 epidemic.
According to the AQEWS on Wednesday, a predominately northwesterly surface wind with a speed range of 8 to 14 km/h was expected. On Thursday, the surface wind was most likely coming from the west/north at 6–12 km/h. On Friday, winds are predicted to blow from the west or northwest at 8 to 16 km/h.