Delhi’s pollution drops to 7-day low but stays in ‘very poor’ zone

Delhi’s air quality improved on Tuesday, but stayed in the ‘very poor’ category, as wind speeds ranged between 10-12 km/hr during the day, helping pollutants disperse.

Delhi recorded a 24-hour average air quality index (AQI) of 328 (very poor) on Tuesday, down from 389 on Monday, according to the Central Pollution Control Board’s 4pm bulletin.

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Winds did, however, get significantly slower in the evening, falling to speeds of less than 3km/hour after 5.30pm. Weather officials forecast that calm conditions from Wednesday will see the pollution take a turn for the worse, adding that Delhi could receive light rain on Thursday, as a western disturbance approaches.

“Local surface winds were relatively strong on Tuesday, leading to an improvement, but the AQI remained within the ‘very poor’ category. On December 1 and 2, winds are likely to be calm, reducing ventilation and leading to deterioration in the air quality,” said the System of Air Quality and Weather Forecasting And Research (Safar), a body under the ministry of earth sciences.

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Gufran Beig, founder and project director at Safar said stubble burning season in northern states was at its end, with farm fires contributing to just 1% of Delhi’s PM2.5 (ultra-fine polluting particles) count on Tuesday.

“Only 186 fires were recorded across the northern plains. Wind speeds will again drop from Wednesday and a low mixing layer will also influence pollution levels,” he said.

Delhi recorded a minimum temperature of 9.8 degrees Celsius on Tuesday, while the maximum was 25.6 degrees, both around the normal mark for this time of the year.

“Delhi is expected to see two western disturbances in the first week of December. While the first may bring light rain on December 2, the second could bright light rain on December 6,” said RK Jenamani, scientist at IMD, stating showers will drop the day-time temperature, but minimum temperature will rise during these two spells. He said while November tends to see one to two WDs each year, December generally sees two to three WDs. “We are already expected to see two of these WDs and this can help the air quality,” he added.

According to the seven day forecast by the Early Warning System (EWS) for Delhi, the air quality will remain in the ‘very poor’ category, unless Delhi receives significant rain.

“From December 1, the air quality is likely to deteriorate but will remain in the ‘very poor’ category and PM 2.5 will be the prominent pollutant during this period,” said the daily bulletin released by the EWS.