Delhi air pollution worsens to severe category, set to be worst since Dec 2021
Some respite was expected from November 4 under the influence of a western disturbance, which is expected to lead to a change in wind direction
Pollution levels in Delhi deteriorated on Tuesday to the severe category with an air quality index (AQI) of 426 at 9am, the highest so far this year. The city was set to record its worst air pollution levels since December 26, 2021, when the AQI was 459, amid an increase in farm fires and meteorological conditions favourable to the accumulation of pollutants. Some respite was expected from November 4 under the influence of a western disturbance, which is expected to lead to a change in wind direction.
On January 2 this year, Delhi recorded an AQI of 404. On Monday, it was 392 (very poor), according to the Central Pollution Control Board (CPCB)’s bulletin released daily at 4pm. The AQI was 352 (very poor) on Sunday.
Data from CPCB’s Sameer app showed at least 26 out of the 37 ambient air quality monitoring stations recorded severe category pollution at 9am on Tuesday. Burari Crossing reported the highest AQI (477), followed by Jahangirpuri (475) and Sonia Vihar (469).
An AQI between zero and 50 is classified as good, 51 and 100 satisfactory, 101 and 200 as moderate, 201 and 300 poor, 301 and 400 as very poor, and 401 and 500 as severe.
Experts said the pollution from stubble burning was rising with an increase in farm fires while meteorological conditions such as calm winds, low temperatures, and a low mixing height were also favourable for the accumulation of pollutants.
India Meteorological Department (IMD) scientist V K Soni, who is also part of the Commission for Air Quality Management, said mostly calm winds from the northwesterly direction and stable atmospheric conditions are favourable for the accumulation of pollutants. He added the mixing layer height, within which pollutants get trapped, was dropping and was currently less than 500 metres. “This is why pollutants are unable to disperse and a haze is visible,” he said.
IMD scientist R K Jenamani said calm wind conditions and a strong northwesterly will persist until November 4 onwards when the western disturbance is expected to bring some respite. “While this... [western disturbance] will be far from Delhi-NCR [National Capital Region], it will lead to a change in wind direction to easterly and may increase local wind speed too.”
Farm fires have spiked across the northern plains. On Monday, 2,221 fires were recorded in Punjab, Haryana and Uttar Pradesh compared to 1,916 a day earlier. A thick layer of smoke could be seen across the Indo-Gangetic Plains through Nasa’s satellite imagery.
The contribution of stubble burning to Delhi’s PM 2.5 levels on Monday was pegged at around 17%, according to the earth sciences ministry and the Indian Institute of Tropical Meteorology’s Decision Support System, which the CAQM uses.
System of Air Quality Management and Weather Forecasting And Research (Safar), which also comes under the earth sciences ministry, said the contribution was around 22%. On Sunday, Safar said the contribution of stubble burning was at a season-high of 26%. It was expected to remain similarly high with northwesterly winds blowing towards the capital.
Delhi recorded a minimum temperature of 15.2 degrees Celsius on Tuesday morning, a degree below normal, and the maximum was expected to be around 32 degrees.