NEW DELHI: After a marked improvement for 24 hours, the city’s air quality plunged back to the ‘very poor’ zone on Wednesday, as local surface winds slowed down. Also, the national capital saw its coldest morning of the season with the minimum temperature falling to 9.2 degrees Celsius.
With winds slowing and cold conditions setting in, air quality is likely to deteriorate further over the next two days, government agencies said. As per the Central Pollution Control Board (CPCB), Delhi’s overall air quality index (AQI) on Wednesday was 361 in the higher end of ‘very poor’ zone, as against 281 in the ‘poor’ zone. On Tuesday, strong winds helped improve air quality, with the city seeing a ‘poor’ day in over 22 days.
According to the India Meteorological Department (IMD) officials, local surface winds slowed down because of a change in wind direction to easterly/south-easterly from north-westerly on Wednesday. “The transition period always slows down the winds as they become calm, which is extremely unfavourable for dispersion of pollutants and thus the spike in pollution levels observed today. Winds are likely to remain calm over the next two days and are likely to return to north-westerly from 28 November, when air might get better,” said a senior IMD scientist.
On Wednesday, the minimum temperature was 9.2 degrees C, two notches below the season’s average and the maximum settled at 28.8 degrees C, two notches above normal. “The night temperature may fall to 8-9 degrees C by the weekend while fog conditions are also likely to occur during this time,” he said.
The union government’s System for Air Quality and Weather Forecasting and Research said that local surface winds are relatively low for the next three days, which reduces dispersion of pollutants. “Air quality is likely to be in the higher end of ‘very poor’ category for the next two days. On 27 November, local surface winds are likely to increase resulting in improvement of air quality but expected to be within the ‘very poor’ category,” it said.