Shallow fog envelopes Delhi as air quality worsens

Shallow fog enveloped Delhi on Monday morning as the mercury was likely to plunge to 8 degrees Celsius while the air quality worsened to the very poor category.

According to the Central Pollution Control Board, the hourly air quality index (AQI) was 307 at 7am. On Sunday, the average 24-hour AQI was 259 (poor).

An AQI between zero and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, 301 and 400 very poor, and 401 and 500 severe.

On Sunday, the government’s monitoring agency System of Air Quality and Weather Forecasting and Research said fine particles (size < 2.5 micrometer) contributed ~ 72% to PM10.

“For the next 3 days, surface wind speed (Calm to 12 km/h) and temperature (Max 19-18 deg C; Min 6-4 deg C) are likely to worsen air quality. Mixing layer height is likely to be ~ 1.0 km that helps dilution of pollutants.”

It added the air quality was likely to deteriorate but remain within the poor or lower end of the very poor categories for the next three days due to low temperatures, which help accumulation of pollutants, and low surface winds that weaken their dispersion. “Morning fog continues to persist due to cold, dry wind flow from [the] northwest region.”

On Monday, the maximum temperature was likely to be 21 degrees Celsius. The minimum temperature on Sunday was 7.6 degree Celsius, and the maximum was 21.1, one degree above normal.