Despite the continuous burning of firecrackers and rising fire counts from neighbouring states, Delhi woke up to a relatively clear morning the day after Diwali. In what has come as a welcome surprise to many, the Air Quality Index (AQI) for Delhi continued to hover over ‘very poor’ levels and did not breach the ‘severe’ mark despite the high emissions as was earlier predicted.
This is a far cry from last year, when a dense toxic smog covered the national capital the day after Diwali, which was celebrated on November 4. The air quality had begun to deteriorate to severe levels by 8pm on Diwali night and peaked at 9pm, with AQI at almost all monitoring stations across the national capital above 450.
An AQI of 300 to 400 is termed ‘very poor’, while above 400 falls in the ‘severe’ category. This year, AQI remained between 350 and 380 across most parts of the city till late on Monday night.
As per SAFAR India, run by scientists from Pune-based Indian Institute of Tropical Meteorology (IITM), the AQI for Delhi on Tuesday morning is around 323 (lower-end of very poor), while it is 342 (very poor) for Noida, and 245 (poor) for Gurugram. The PM2.5 levels recorded at 10am stood at 190 ug/m3. It is expected to improve further to 150 ug/m3 by Wednesday.
WINDS OF CHANGE?
Diwali not only arrived earlier this year when winter is yet to set in fully, but the weather also played a pivotal role. According to Dr Gufran Beig, founder of SAFAR India, the relatively warmer conditions and prevailing winds ensured the dispersion of pollutants that may have otherwise accumulated and worsened the air quality.
“The surface wind speed was expected to pick up from Tuesday afternoon. However, that happened a little earlier than usual. Even though it was slightly cold, the winds prevailed. Stagnant conditions did not arrive and the accumulation of PM2.5 did not happen. In fact, the dispersion is expected to get faster from Tuesday afternoon,” he told News18. “Even if the air quality had dropped to severe levels on Diwali, it was not expected to be a prolonged event due to favourable meteorological conditions this time. This was perhaps the cleanest Diwali since 2015.”
As per the assessment, the local surface winds remained moderate at 8-16 km/h with maximum temperature around 31-32 degree Celsius and are likely to remain so over the next two days, which will help in better dispersion of emitted pollutants. The AQI is likely to improve further by Wednesday.
FIRE COUNTS RISING
Despite the ban, firecrackers were still being burnt across the national capital region (NCR), and according to Dr Beig, it is difficult to rule out if the incidents were lesser post-midnight, which is the time when maximum stagnation happens.
Meanwhile, another contributing factor — the fire counts over the neighbouring states of Punjab and Haryana — remained on an ascending trajectory, and crossed nearly 1,450 on Monday. While the overall impact of stubble burning on Delhi’s air quality has remained negligible so far, it has begun to increase since last week. According to SAFAR India, it is expected to rise to nearly 10 per cent due to favourable transport-level wind flow from north-west and west directions.
“Even though the fire emissions were high, the wind direction was such that the intrusion of smoke in Delhi was minimal. The winds were westerly/south-westerly, mostly coming from Afghanistan and the Gulf, instead of north-westerly which is usually to blame for the pollutants from crop fires to drift towards Delhi,” said Beig.
WORD OF CAUTION
Though the air quality did not deteriorate to severe levels, it could still have an adverse impact on people breathing such polluted air for a very long time, leading to a significant increase in respiratory problems. While there is already an advisory for people to reduce heavy exertion, those suffering from heart or lung disease — especially older adults and children — need to take adequate care.
As the temperatures plummet further and winter sets in, the stagnation of pollutants is likely to make air quality worse. Despite a ‘relatively better AQI’ this Diwali, the national capital remains one of the most polluted cities in the world.
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