Experts on Thursday warned that violations of the ban on firecrackers on Diwali, coupled with slower, north-westerly winds carrying stubble burning smoke, will likely push Delhi’s air pollution back into the ‘severe’ levels it witnessed earlier this week.
Scientists at the India Meteorological Department (IMD) said that even though the city’s air quality index (AQI) improved to the lower range of ‘very poor’ on Thursday, thanks to stronger winds, the situation will likely deteriorate from Friday.
Data from the Central Pollution Control Board (CPCB) data shows that on Thursday, Delhi’s overall AQI was 314, in the ‘very poor’ category. On Wednesday, the AQI was 344, also very poor.
Diwali will be celebrated on Saturday.
VK Soni, head of IMD’s environment monitoring research centre, said winds blowing over Delhi will start slowing down from Friday, and their direction will switch to north-westerly, which will increase the contribution of stubble-burning smoke from Punjab and Haryana.
“Even though we have forecast that this Diwali is likely to be better compared to the last few years, the weather is expected to be unfavourable. If people in the city burst crackers, then the pollution level could slip to ‘severe’ on Diwali day and a day after,” Soni said.
The Capital’s AQI was ‘severe’ for six days, starting November 6. The city got minor relief on Wednesday and Thursday, when the AQI was very poor category after winds shifted direction, blowing in from the east, and carrying minimal smoke from farm fires.
Smoke from farm fires contributed to just 3% of Delhi’s PM2.5 (ultrafine particulate matter less than 2.5 micrometres in diameter) levels on Wednesday, the lowest since October 14.
Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, said that from Diwali afternoon the wind speed will dip to nearly 6kmph.
“From Diwali evening the air quality is likely to start deteriorating. However, from Sunday night the wind direction is expected to change again to easterly and there is also a possibility of light rain,” Srivastava said.
The IMD forecast said that wind speeds are likely to improve from Monday.
The Union ministry of earth sciences’ air quality monitoring centre, System of Air Quality and weather Forecasting and Research (Safar), also released a similar forecast for Delhi’s air quality for the Diwali weekend.
“The stubble burning induced impact in AQI is expected to increase from negligible to moderate for the next two days,” the Safar forecast read.
The forecast, however, said that even if residents do not burn any crackers, the PM2.5 level is still expected to be on the higher-end of ‘very poor’ or the lower-end of ‘severe’ category.
However, despite unfavourable weather conditions, the forecast said the AQI is expected to be better this year, as compared to Diwali day and the days after the festival for the past four years.
“Even a smaller increment in the local additional emission is likely to have significant deterioration impact on November 14 and November 15, and may push the AQI in the severe category,” read the Safar forecast.
