At 7am on Tuesday, when the temperature dropped to 9 degrees Celsius, Delhi’s Air Quality Index (AQI) registered as 281 in the poor category. At 4 pm on Monday, the AQI was 310, falling into the very bad category. Because of the strong surface breezes that allowed pollutants to scatter, the weather was predicted to stay bad at least through Thursday.
Low temperatures, especially at night, cause the mixing height, a layer of the atmosphere where pollutants can accumulate, to decrease. However, a good mixing height—an invisible layer of the atmosphere where pollutants become trapped—and strong surface winds during the day are also likely to aid in the dispersion of pollutants.
According to the Early Warning System for Delhi, which the Commission for Air Quality Management in the NCR employs to take preventative action against pollution, Delhi’s AQI is unlikely to reach a severe level by the end of the month.Up until Thursday, the AQI is anticipated to be in the poor category, and the forecast for the following six days indicates that the air quality is likely to stay primarily in the poor to very poor category.
The minimum temperature on Monday was 8.9 degrees Celsius, which is the lowest so far this season and three notches above average. For the first time, the temperature fell below the magic number of 9.
Since Friday, when it fell to 9.6 degrees Celsius, Delhi’s minimum temperature has been below 10 degrees. On Saturday, it was 9.0 degrees, on Sunday it was 9.6 degrees, and on Monday, it was 8.9 degrees. The frigid northwesterly winds moving toward the city are mostly to blame for the temperature dip. The dip could go even lower.
“The impact on temperature, especially at night, increases the longer these northwesterly winds persist.” By Thursday, the minimum temperature may reach 8 degrees, according to an official.
Delhi experienced the coldest minimum temperature of 9.2 degrees Celsius on November 24 of last year. It dropped as low as 6.3 degrees Celsius in 2020. (November 23). The lowest minimum temperature in November 2019 was 11.4 degrees (November 20).