Strong local winds help AQI in Delhi to stay poor

Delhi’s air quality deteriorated on Thursday but remained in the ‘poor’ category for a second consecutive day, with an air quality index (AQI) value of 295, according to the Central Pollution Control Board’s national bulletin released at 4 pm

Delhi’s air quality deteriorated on Thursday but remained in the ‘poor’ category for a second consecutive day, with an air quality index (AQI) value of 295, according to the Central Pollution Control Board’s national bulletin released at 4 pm.

New Delhi, India - November 10, 2022: A clear sky seen at Kartvya Path/ near India Gate, in New Delhi, India, on Thursday, November 10, 2022. Strong surface winds brought some relief from high pollution levels in Delhi and improved visibility. (Photo by Raj K Raj/ Hindustan Times) (Hindustan Times)

In comparison, the Capital’s AQI was 260 on Wednesday. Officials said the wind changed direction on Thursday, allowing stubble intrusion to reach Delhi, but local wind speeds remained strong and did not allow the air quality to deteriorate significantly.

In wake of this spell of relatively clean air, the Commission for Air Quality Management (CAQM) will hold a review meeting on measures of the Graded Response Action Plan (Grap) on Friday, officials said. “The CAQM is keeping a close watch on the changing air quality scenario of Delhi-NCR and accordingly, the Sub-Committee of the Commission on Grap will convene a meeting tomorrow (Friday) to comprehensively review the situation for appropriate decision,” the CAQM said in a statement.

Forecasts by the Early Warning System (EWS) for Delhi, used by CAQM to take pre-emptive action under Grap, shows the city’s AQI is likely to remain ‘poor’ until at least November 13.

VK Soni, scientist at IMD and part of the CAQM sub-committee on Grap, said despite the intrusion from farm fires, local wind speeds did not allowing pollutants to accumulate. “We will continue to see strong winds in the next two days and this will negate the impact of stubble emissions. Overall, AQI should remain in the ‘poor’ range,” he said.

Meanwhile, the System of Air Quality of Weather Forecasting and Research (Safar), a government body, said the contribution of stubble burning to Delhi’s PM2.5 pollutants was 8% on Wednesday -- up from a contribution of 5% on Wednesday.

According to Safar, the rate of inflow of pollutants is also expected to be higher over the next two days, with the body predicting that the AQI will deteriorate to ‘very poor’.

“The air quality is likely to be ‘very poor’ category for the next two days, owing to strong upper-level windflow blowing from the northwest direction, therefore enhancing transport of pollutants,” said Safar.

Delhi recorded a maximum temperature of 29.5 degrees Celsius on Thursday, which is around normal for this time of the year. The minimum was recorded at 16.8°C -- three degrees above normal. The forecast for Friday shows the maximum temperature is likely to remain around 29°C, while the minimum will hover closer to the 16-degree mark.