Delhi pollution: Rain, less stubble fires and wind reduce AQI

Day after Diwali a surprise shower, cool surface wind and relatively less stubble burning activity in the vicinity of the national capital brought down Delhi`s air quality index from 525 to 273 within 24 hours.

Delhiites relaxed a bit as they could comparatively breathe better on Monday after consistently battling the severe level of air quality which persisted over a week.

The Central Pollution Control Board of India recorded a significant improvement of the ambient air quality from 525 on Sunday to 273 on Monday.

As per the Ministry of Earth Science officials, surface winds which are blowing in northeasterly direction (not favourable for stubble-burning smog from entering Delhi), besides scattered rainfall in Delhi and surrounding region have washed out some of the pollutants, bringing down the AQI reading.

The System of Air Quality and Weather Forecasting and Research (SAFAR) recorded the overall AQI of the national capital at 319. The CPCB notified the overall air quality of Delhi in the upper end of "Poor" category while the SAFAR monitored it in the lower end of the "Very Poor category".

An AQI between 0-50 is marked "good", 51-100 is "satisfactory", 101- 200 is "moderate", 201- 300 is "poor", 301-400 is "very poor" and 401-500 is considered "severe". The AQI beyond 500 is termed as an emergency situation and calls for equivalent measures.

The morning after Diwali celebration, a thick blanket of noxious smog enveloped the national capital and shot up the pollution in the city to "emergency` level on Sunday where the hourly average concentrations of PM 2.5, a deadly pollutant, touched more than 1000ug/m3.

While SAFAR mentioned Delhi`s AQI in Very Poor, it stated that the AQI is likely to improve further during the day and settle at the POOR category.

The overall air quality of Delhi is in the lower end of the Very Poor category today morning as forecasted. AQI is likely to improve further during the day and reach the POOR category. Surface winds are northeasterly direction and energetic, very favorable for pollutant dispersion. Scattered rainfall in Delhi and observed surrounding regions has washed out some of the pollutants," the ministry said.

Drastic reduction in the stubble fire counts also played a major role in improving the air quality. "The stubble fire counts with sufficient potential estimated from SAFAR-multi-satellite products are significantly reduced and are around 282. Stubble burning share in PM2.5 in Delhi`s air is almost negligible and estimated as 1 per cent for today," the officials added.

The officials further added that the boundary layer wind direction is northeasterly which is not favourable for fire-related transport. However, a change in boundary layer wind direction is forecasted by Tuesday afternoon, but since the fire-related emissions have reduced, a significant impact of such incidents on the air quality is not expected.

For Tuesday, Wednesday and Thursday, the ministry forecast the AQI to marginally deteriorate and stay in the "Very Poor category".
 

The story has been taken from a news agency