Delhi’s air quality deteriorated on Wednesday morning and was likely to worsen to the poor category by the end of the day even as a change in wind direction brought the minimum temperature below 20°C (19.4°C) after five days.
An average air quality index (AQI) of 196 (moderate) was recorded at 8am compared to 180 (moderate) a day earlier. The change in the wind direction to northwesterly and a drop in local wind speed was likely to keep the air quality poor for the next two days
Cold northwesterly winds negatively impact air quality. A dip in temperature slows down the dispersion of pollutants and also brings smoke from the fields of Haryana and Punjab, where farm fires are recorded around this time of the year.
The minimum temperature dipped below the 20°C mark for the first time since Friday when it was 18.6°C. A change in wind direction followed and the minimum temperature rose to 20.9°C on Saturday. On Sunday, it rose to 23.1 and to 24.4°C on Monday. Delhi’s minimum on Tuesday was 22.7°C, two degrees above normal.
“With a change in wind direction, clear skies will return. Northwesterly winds are also cooler, so the minimum is expected to be below 20°C,” said an India Meteorological Department official.
According to an Early Warning System (EWS) forecast, the air quality was likely to be in the lower end of the poor category until Friday. “The outlook for the subsequent six days shows the air quality is likely to hover between poor and moderate.”
