As wind speed picks up, Delhi air quality stays in check

Delhi's air quality worsened to the "moderate" category, with an AQI of 193, and is forecasted to reach "poor" by Thursday. Cold northwesterly winds are contributing to the decline in air quality as they transport smoke from farm fires in neighboring states. The minimum temperature dipped below 20 degrees Celsius, slowing down the dispersion of pollutants. Measures have been implemented to mitigate the situation, including shutting down construction sites and encouraging unified commuting. The maximum temperature will remain around 35 degrees Celsius, while the minimum temperature is expected to drop to 18 degrees Celsius.

Delhi’s air quality deteriorated on Wednesday, but remained in the “moderate” category, after wind speed picked up during the day. Delhi’s 24-hour average air quality index (AQI) was recorded at 193 (moderate) — up from 180 (also moderate) recorded a day earlier. The forecast showed AQI is likely to touch “poor” by Thursday, and may remain in the same zone over the weekend.

Tilak Marg covered with smog in New Delhi on Wednesday morning. (Arvind Yadav/HT Photo)

A change in wind direction to the northwesterly, meanwhile, once again brought Delhi’s minimum temperature below the 20-degree mark, at 19.4 degrees Celsius (°C), one degree below normal, on Wednesday morning. In comparison, it was 22.7°C on Tuesday.

Cold northwesterly winds are known to negatively impact air quality as a dip in temperature not only slows down the dispersion of pollutants, but these winds also transport smoke from the fields of Haryana and Punjab, where farm fires are being recorded every day.

“Delhi’s air quality is likely to be towards the lower side of ‘poor’ category from Thursday till Saturday. The outlook for the subsequent six days shows the air quality is likely to remain in between ‘moderate’ and ‘poor’,” said the Early Warning System (EWS) for Delhi. EWS is a forecasting system under the ministry of earth sciences and used by the Commission for Air Quality Management (CAQM) to take pre-emptive action.

Delhi recorded its first “poor” air day this winter on Friday, when the AQI was recorded at 212. On the same day, CAQM invoked Stage-I measures of the Graded Response Action Plan (Grap). These measures include shutting down construction and demolition sites over 500sqms but are not registered with the government on its “web portal” for dust management, encouraging offices to start unified commute for its employees to reduce road traffic, periodic mechanised sweeping and water sprinkling on roads and deployment of traffic police at all identified corridors with heavy traffic.

The next day, the AQI deteriorated further to 216 (poor), before improving and returning to the “moderate” range. Delhi’s AQI has been “moderate” since Sunday, after a change in wind direction to easterly raised the mercury once again. The AQI had briefly touched 200 on Wednesday morning, before an increase in wind speed post noon brought an improvement.

Delhi’s maximum temperature was recorded at 35 degrees Celsius, one degree above normal. Forecasts showed that while the maximum temperature will continue to hover around 35 degrees Celsius for the next few days, the minimum temperature is likely to drop further, to around 18 degrees Celsius over the next two days.