Change in wind may lead to worse air over weekend in Delhi

On Friday, city’s AQI remained in the poor category at 261, with northwesterly winds causing nippy nights but warm and slightly windier afternoons

Delhi’s air quality is likely to dip over the weekend due to a change in wind patterns, government forecasting agencies said on Friday, predicting still conditions that will likely trap pollutants in the air and drive up the air quality index (AQI).

A smoggy morning at Kartavya Path on Friday. (Arvind Yadav/HT Photo)

On Friday, the city’s AQI remained in the poor category at 261, with northwesterly winds causing nippy nights but warm and slightly windier afternoons. From Saturday, the wind direction will change to southeasterly.

“Delhi’s air quality is likely to be in the ‘poor’ category on Friday and in the ‘very poor’ category from Saturday to Monday. The outlook for the subsequent six days shows that the air quality is likely to remain in the ‘very poor’ to ‘poor’ category,” said the Early Warning System (EWS) for Delhi, which comes under the ministry of earth sciences.

“In the last few days, we have been recording a similar trend where winds become calm at night and pick up from around 8 am onwards,” said Kuldeep Srivastava, a scientist at IMD.

“This wind speed once again dips in the evening, as the temperature begins to drop. The wind direction is forecast to change to southeasterly over the weekend, which may lead to deterioration in air quality once more,” he added, stating that this was due to a trough forming over Rajasthan. “Wind speed may dip during this transition and pollutants can accumulate over Delhi-NCR again,” he said.

To be sure, southeasterly winds will help reduce the impact of smoke from farm fires.

The slight deterioration in air quality over the last 24 hours was aided by a dip in minimum temperature too, which stood at 15.2 degrees Celsius on Friday – two degrees below normal and the lowest so far this season. It was 15.8 degrees Celsius a day earlier. The lowest minimum before Friday was 15.6 degrees Celsius on October 22.

Met officials said the dip so far was due to cold northwesterly winds blowing towards Delhi. With southeasterly winds returning – which are warmer – this minimum will also rise. The minimum is predicted to hover around 16 degrees Celsius on Saturday, before rising by a degree to 17 degrees on Sunday, a level at which it will till the end of the month.