Brief reprieve as wind pulls AQI out of ‘severe’

There was a significant improvement in Delhi’s air quality on Saturday, although it still remained very poor, after winds picked up and switched directions, helping reduce the impact of farm fires and blowing away some of the emissions originating in local sources

There was a significant improvement in Delhi’s air quality on Saturday, although it still remained very poor, after winds picked up and switched directions, helping reduce the impact of farm fires and blowing away some of the emissions originating in local sources.

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The 24-hour air quality index at 4pm dropped to 381 from 447 the day before, according the Central Pollution Control Board’s AQI bulletin. By 9pm, the number further improved to 363.

“Improvement in air quality started Friday night. Since the AQI data is a 24-hour average, the impact on the numbers will be seen more visibly in Sunday’s bulletin,” a scientist at the Indian Institute of Tropical Meteorology said, asking not to be named. “However, the AQI is likely to remain in the ‘very poor’ zone because the accumulation of pollutants is so high, these winds aren’t enough to display a significant improvement.”

The improvement also may not signal the worst may be over just yet. In Punjab and Haryana, the number of farm fires rose once again after a recent dip. On Saturday, 2,907 incidents were recorded via satellites in these regions, up from 2,500 the day before.

As per the trends of previous years, farm fires peak between November 3 and November 10. So, we are at the onset of the peak of stubble burning. Farm fires will continue for the next one week. However, the quantum will remain lower than the previous year,” said a Punjab Pollution Control Board (PPCB) official, asking not to be named.

Saturday was also the first day of new curbs to combat the problem – diesel cars that do not conform to the new BS-VI emissions standards and primary schools were shut for offline classes. Officials said for the enforcement of the first curb, the focus was mostly on raising awareness and issuing warnings.

Any violation of the diesel ban (also covered under the restrictions are petrol vehicles that are on the BSIII emission norm) will attract a fine of ₹20,000.

The slight fall in pollution levels was primarily because of a change in wind patterns on Friday night, the IITM scientist said. From northwesterly winds, which carry smoke from the stubble fires being lit in the agrarian states of Punjab and Haryana upwind, the direction changed to south-easterly. Wind speed also improved slightly due to an active western disturbance over the region.

Delhi’s foul air is mainly the result of the high count of stubble fires this year, primarily in Punjab, he said.

The air quality bulletin released by the earth science ministry’s Decision Support System (DSS)—a pollution monitoring and forecasting model developed by IITM—said that on Saturday, the prominent surface winds in Delhi were south-easterly, blowing at a speed of 8-12kmph. The mixing depth—the height above the surface throughout which a pollutant such as smoke can be dispersed—was 1,200m, which is expected to improve to 1,350m on Sunday.

As many as 2,817 of farm fires were reported from Punjab, and 90 from Haryana on Saturday, according to government data.

Pollution levels are expected to shoot back up from November 9 as temperatures are expected to start falling, said Mahesh Palawat, vice-president of meteorology and climate at Skymet Weather Services, a private forecaster.

“Currently, we are recording above normal temperatures, which are still a factor that is favouring dispersion of pollutants to some extent,” Palawat said. “From November 9, the temperatures are likely to start falling and that might result in pollution levels rising.”