NEW DELHI: Clouds and haze enveloped the city on Thursday as air quality plunged again to the ‘severe’ zone after remaining ‘very poor’ for the past three days. Also, at 19.8 degrees Celsius, five notches below the season’s average, Delhi recorded its lowest maximum temperature of the season so far.
Overcast skies, low temperature, calm winds and very light rain adding to the high humidity levels trapped the pollutants, leading to further deterioration of the air quality. Weather officials said the air is likely to remain bad over the next two days as well.
As per the Central Pollution Control Board (CPCB), Delhi’s 24-hour average air quality index (AQI) was 429 in the ‘severe’ zone, up from 370 in ‘very poor’ category the previous day. Last month saw 11 ‘severe’ days, the highest number of days in this category recorded over the past six years.
Delhi saw a ‘severe’ smog episode from November 25 when the AQI remained above 400 (extremely unhealthy across all age groups) till November 28. The air quality improved slightly from November 29 but again reached the upper end of ‘very poor’ on Wednesday.
While stubble burning has come down drastically, adverse weather conditions and local sources of pollution are the major factors pushing down the air quality, data from the Indian Institute of Tropical Meteorology’s (IITM) decision support system showed. While vehicular emissions contributed 20% to overall pollution, Delhi and peripheral industries contributed 9%. “It is mainly because of the local pollution and low boundary layer on which pollutants settle. Since there is no dispersion because of stable weather, the air quality is staying bad,” a senior IITM scientist said.
According to the India Meteorological Department (IMD), on Thursday the Safdarjung Observatory recorded 1mm rainfall till 5.30pm. “The very light rain actually added to the problem. Had it rained well, the pollutants would have been washed out,” said a senior IMD scientist, who didn’t wish to be named.
On Thursday, the maximum temperature was 19.8 degrees C, five notches below normal — lowest maximum temperature this season so far. The minimum settled at 13.4 degrees C, four notches above normal. Mahesh Palawat, vice-president, Skymet, a private weather forecaster, said that less rainfall and high moisture allowed further trapping of pollutants, which led to the spike.
“The Western Disturbance that struck Delhi resulting in cloudy skies and light rain was not strong enough and hence, didn’t induce good showers. Also, variable light winds didn’t allow any dispersion. There might be slight improvement over the next two days but any real change may be expected only after December 7-8,” he said. Meanwhile, IMD officials said the temperatures will start dropping from December 7-8 when winds from the Himalayan region are likely to return to the national capital.