Delhi’s air quality turns severe, no relief in sight till next week
The air quality in the city deteriorated on Thursday, and was on the brink of the “severe” category, according to the Central Pollution Control Board’s daily bulletin, before plunging into deep red later in the evening, as calm surface winds were unable to disperse pollutants.
Delhi’s average air quality index (AQI) touched 400 – just point short of “severe” -- in the 4pm reading that is taken as the pollution marker for the day. By 9pm, the average climbed to 401, and was on an upward trend at several stations across the city. The Capital has seen a sudden drop in air quality in the past 48 hours: it was 290 (poor) on Tuesday and 361 (very poor) on Wednesday.
Weather forecasting agencies said no immediate relief is expected as calm conditions are likely to continue till November 28, after which wind speeds may increase to 15-20 km/hr on Monday, facilitating the dispersal of pollutants.
According to Gufran Beig, founder and project director at the Centre-run System of Air Quality and Weather Forecasting and Research (Safar), calm wind conditions will prevail at night and in the early hours of the morning for the next three days. “A combination of local emissions and weather conditions are playing a part now, with stubble burning reducing considerably,” said Beig.
The share of stubble burning in Delhi’s PM 2.5 concentration was 6%, with 219 fires recorded by Safar across the northern plains.
“On November 29, local surface winds are likely to increase, resulting in improvement of air quality, but even then, it will be within the ‘very poor’ category,” Beig added.
Delhi recorded a minimum temperature of 9.7 degrees Celsius (°C) on Thursday, 0.5 degrees above Wednesday’s minimum temperature of 9.2°C.
Mahesh Palawat, chief meteorologist at private forecasting agency Skymet, said temperatures are not likely to dip below 9°C this week. “Temperatures will hover around 10-11 degrees for the next few days,” he said, and concurred with Safar’s forecast of three more high-pollution days until Monday.
According to Early Warning System (EWS) for Delhi – another forecasting mechanism under the ministry of earth sciences -- a combination of low wind speed and a low ventilation index was negatively impacting Delhi’s air.
While wind speed in the city touched 10km/hr during the day on Thursday, EWS said, it will drop to a maximum speed of 8km/hr on Friday and Saturday, with the Delhi’s ventilation index (measure of the volume rate of horizontal transport of air within the mixing layer) varying from 500-1,500 sqm/second in the next two days.
“A ventilation index lower than 6,000sqm/sec, with an average wind speed less than 10km/hr, is unfavourable for dispersion of pollutants,” it said.
The Delhi government on Thursday announced a ban on construction and demolition activities in the Capital once again, following a Supreme Court on Wednesday reimposing the ban in the wake of deteriorating air quality. Schools and educational institutions in the Capital are set to open next week.