Delhi residents flouted the ban on crackers on Diwali but weather conditions, including strong wind and rain, helped them breathe easier by Sunday evening. The 24-hour average AQI was recorded at 435, in the severe category on Sunday. This was in keeping with the trend observed during at least the past five years, when the day after Diwali is more polluted than the festival day, owing to accumulation of pollutants during the day.
SAFAR had forecast that Delhi’s air would be the best in four years if no crackers are burnt, but several violations of the ban were reported from all parts of the city.
At Anand Vihar, PM 2.5 levels touched 1,661 microgrammes per cubic metre (µg/m3) at 1 am, after a steady increase that started at 7 pm, when it was 496 µg/m3. By 5 pm on Sunday, the concentration had dipped to 172 µg/m3, owing to strong winds that started in the morning and rain in the evening.
At Aurobindo Marg, similarly, PM 2.5 levels touched a peak of 668 µg/m3 at midnight, slowly dipping to 147 µg/m3 at 5 pm.
Strong winds started blowing at around 2 pm on Sunday — an average of close to 11 km per hour, almost twice as high as the previous day. Wind direction too, was southeasterly, which meant stubble burning had only a nominal impact on air quality.
“The magnitude of PM 2.5 within the severe category is found to be more than predicted. This tends to suggest that significant local additional emissions (probably firecracker related) during yesterday night on already high pollutant concentrations led to such a scenario where hourly average concentrations touched more than 1,000 micrograms per cubic metre at midnight. However, there are three very positive developments to follow and a quick recovery from the current scenario is expected,” a SAFAR official said.
SAFAR said that boundary layer winds picked up and changed direction to easterly, which is not favourable for stubble fire-related intrusion.
“Stubble burning share in PM 2.5 in Delhi’s air is almost negligible and estimated at around 4%. Better ventilation conditions are likely to prevail for faster dispersion. AQI is likely to be in the lower end of very poor on Monday, and may touch the poor category in case of enough rains and washout. On Tuesday and Wednesday, it is forecast to stay in the middle-end of very poor,” the weather forecasting agency said.
Temperature expected to dip
The city, meanwhile, is expected to get colder too, with the maximum temperature expected to be 26 degrees Celsius. The minimum temperature is expected to be 11 degrees Celsius.
On Sunday, the maximum temperature was 29.1 degrees Celsius, a degree above normal, while the minimum was 11.4 degrees Celsius, 2 degrees below normal.
At Safdarjung, 0.4 mm of rain was recorded till 5.30 pm. This was 1.8 mm at Palam, 2.5 mm at Pusa Road and 1.2 mm at the Ridge.
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