Slow winds push Delhi air quality to ‘very poor’

Air quality in the National Capital plunged to ‘very poor’ category on Tuesday after remaining in the relatively better ‘poor’ zone for over a week as winds slowed

Air quality in the National Capital plunged to ‘very poor’ category on Tuesday after remaining in the relatively better ‘poor’ zone for over a week as winds slowed down. The air quality index (AQI), as calculated by the Central Pollution Control Board’s (CPCB) 4 pm bulletin, was 364 in the ‘very poor’ category, as against 269 in the ‘poor’ zone on Monday.

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As per scientists at the India Meteorological Department (IMD), the average wind speed was 8-10 kmph on Tuesday, which is not favourable for dispersion of pollutants. According to experts, the ventilation index should be around 12-14kmph for effective dispersal of pollutants.

“The winds have been slow because no system or a Western Disturbance forming over Delhi. The wind speed is expected to pick up on January 23,” a senior IMD scientist said.

As per the system of Air Quality and Weather Forecasting and Research (Safar), a unit of the Union ministry of earth sciences (MoES), low wind speed is the crucial factor leading to deterioration of air quality.

“The forecast suggests the low surface wind condition is likely to continue till Wednesday. The decreased ventilation can lead to further deterioration in AQI pushing it towards the higher end of ‘very poor’ category by tomorrow (Wednesday) morning. A sharp increase in wind speed is expected on January 22, and is likely to flush out accumulated pollutants. A considerable improvement in AQI from the lower end of ‘very poor’ to ‘poor’ is forecast for January 23,” the SAFAR bulletin read.