Cold wave continues; air quality turns 'severe' again

NEW DELHI: It was a cold Thursday morning in the national capital with the minimum temperature settling at 3.7 degrees Celsius, four notches below the season's average, the Met Office said. Delhi's air quality turned severe again on Thursday due to unfavourable meteorological conditions like low wind speed that prevented dispersion of pollutants,

authorities said.

The maximum temperature is expected to hover around 21 degrees Celsius, and the humidity at 8:30 am was 97 percent, an India Meteorological Department (IMD) official said. The Central Pollution Control Board data showed the overall air quality index (AQI) in the severe level of 403, while the Centre-run System of Air Quality and Weather Forecasting (SAFAR) showed an AQI of 372, which falls in the 'very poor' category.

According to CPCB data, 22 areas recorded severe pollution, while 13 areas witnessed 'very poor' air quality in NCR. Ghaziabad and Faridabad recorded severe air quality while Gurgaon and Noida recorded 'very poor' air quality. The overall PM2.5 level –fine particulate matter in the air with a diameter of less than 2.5 micrometer –was recorded at 322 and the PM10 level at 485 in Delhi, CPCB said.

The national capital recorded its second-highest pollution level of the year on Sunday with an AQI of 450. The air quality remained 'severe' on Monday and Tuesday. There was a slight drop in pollution level and the air quality moved to the 'very poor' category on Wednesday.

On Thursday, the air quality again worsened and turned severe. According to the Indian Institute of Tropical Meteorology, the air quality is likely to improve marginally on Friday. The ventilation index is marginally favourable for dispersion of pollutants at 4,500 sqm/second, IITM said.

The ventilation index is the speed at which pollutants can disperse. A ventilation index lower than 6,000 sqm/second, with average wind speed less than 10 kmph, is unfavourable for dispersion of pollutants.