Air Quality Index (AQI), which had remained below 150 for most of December, suddenly jumped to 256 at the monitoring station in Sector 25, Chandigarh, on Saturday morning.

Attributing it to wind systems forming in the region due to western disturbances, experts said the air quality is expected to improve with rain likely for the next few days.

The jump is high considering that at the Sector-25 station, which gives live updates, AQI had gone up to just 140 on Diwali night, though it was recorded higher at other observatories of Chandigarh Pollution Control Committee.

“The air quality turned poor at other stations as well, and the sudden spike is most likely related to some weather phenomena,” said Debendra Dalai, member secretary, CPCC.

Throwing more light on it, Surender Paul, director, India Meteorological Department, Chandigarh, said: “A western disturbance is active in the northwest of the region, and winds from other places are rushing in towards here. The most likely explanation is that winds are coming from in and around Delhi, where air quality is poorer.”

However, with rain likely in the coming days, AQI is likely to fall below 100 again, said Paul.

Central Pollution Control Board classifies AQI of 200-300 as poor. It can cause breathing discomfort to most people on prolonged exposure. AQI of 100-200 is moderate, and can cause breathing discomfort to people with lung and heart diseases. AQI of 50-100 is satisfactory, though it can still cause minor breathing discomfort to sensitive people. Beloe 50, AQI is classified as good and has minimal impact on health.

‘Cleaner air so far has led to colder winter’

Air this winter has been cleaner than in previous years. The average AQI of the city in December 2020 stood at 119, as compared to 140 in December 2019.

Explaining how this made the winter chillier, Paul said: “Pollutants, especially particulate matter, soak up heat during the day and keep the city warm at night. This has been missing this winter and has been one of the reasons why the city has been colder.”

Dalai added that due to less vehicular movement this year, the concentration of greenhouse gases had also come down and made the city a bit more colder this season.

City records 1.1mm rain, more on the cards

Meanwhile, western disturbances started affecting the region, with 1.1mm rain recorded in the city on Saturday. Chances of rain are likely to increase from Sunday, and up to 30mm along with thunderstorm is likely on Monday .

Sunday was a cold day as maximum temperature fell from 17.4°C on Saturday to 15.7°C, five notches below normal. Minimum temperature remained unchanged at 6.1°C. A cold day is declared when maximum temperature is more than 4.5°C below normal and minimum temperature is less than 10°C.

In the next three days, maximum temperature will remain between 16 and 17 degrees while minimum will remain between 8 and 10 degrees, according to the weather bulletin.

Source: January 02, 2021, Hindustan Times