Delhi’s air quality in ‘severe’ category as stubble burning add to woes

Forecasts at present show Delhi’s AQI could remain ‘severe’ until Saturday, before local wind speeds pick up once again

Delhi’s air quality deteriorated in the last 24 hours, returning to the ‘severe’ category with an air quality index (AQI) of 431 at 11am on Thursday, with calm winds overnight and intrusion from stubble burning creating a haze over the city.

Farm fires in Punjab, Haryana and Uttar Pradesh had doubled in numbers on Wednesday. (ANI image)

While wind speed dropped overnight, allowing local emissions to accumulate in the air, strong north-westerly winds are also blowing towards the capital at present, facilitating the transmission of stubble emissions to Delhi-NCR and beyond.

Forecasts at present show Delhi’s AQI could remain ‘severe’ until Saturday, before local wind speeds pick up once again.

Farm fires in Punjab, Haryana and Uttar Pradesh had doubled in numbers on Wednesday, touching a figure of 3,825 fires, up from 1,842 fires the region on Tuesday. This is so far the highest single-day count of the season, with numbers expected to rise further today and in the coming days, experts say.

VK Soni, scientist at IMD and part of the commission for air quality management (CAQM) in NCR, said while wind speed may change to southeasterly from Friday onwards, Delhi’s AQI is forecast to stay in the ‘severe’ range till Saturday at the moment, owing to intrusion from farm fires.

“Farm fire count has increased significantly now and while initial forecasts were that the AQI will be between ‘very poor’ and ‘severe’ for Thursday, the AQI has reached severe due to these stubble emissions reaching Delhi. We are also seeing calm winds at night time. With stubble count expected to increase, the AQI is expected to be impacted accordingly,” he said, stating wind speeds increase during the day, when the sun comes out, allowing for some dispersion to take place.

Delhi’s AQI had improved to the ‘very poor’ category on Wednesday, dropping to a reading of 376 (very poor) as wind speeds were fairly strong during the day, oscillating between 5-20 km/hr. At the same, winds at the transport level – upper-level winds which bring pollutants from far-away places – were slow and did not significantly impact Delhi’s AQI. On Tuesday, Delhi’s AQI had been in ‘severe’, with the AQI of 424 also making it the most polluted day of the year thus far.

Gufran Beig, project director at the System of Air Quality and Weather Forecasting and Research (Safar) said early estimates by their model indicate the contribution of stubble burning to Delhi’s PM 2.5 is 38% today, making it the highest single-day count so far.

“The AQI across most of NCR is in ‘severe’ and the AQI at Noida is there worst, where it is close to 500. Gurugram and Lodhi road are the least affected locations. We are seeing the highest values at locations that are in the path of stubble burning, including Noida,” said Beig, stating dispersal of existing pollution levels will only take place significantly from Saturday evening.

“Wind speed will increase and allow dispersion from Saturday evening. Before that, no significant dispersion will take place as impact from stubble burning is high,” he said.

An AQI between zero and 50 is classified as “good”, 51 and 100 is “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor”, and 401 and 500 is “severe as per the CPCB.

Delhi recorded a minimum of 15.8°C this morning, which is around normal for this time of the season. The maximum is expected to be around 32°C on Thursday, IMD’s forecast shows.