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Wind speed brings down AQI but farm fires double

ByJasjeev Gandhiok, Soumya Pillai and Vishal Rambani, New Delhi/sangrur
Nov 03, 2022 12:56 AM IST

Farm fires in Punjab surged to their highest levels this season, prompting experts to sound warnings of severe air pollution in the Capital in the coming week even though there was a slight respite on Wednesday, and sparking a political war of words over the annual crisis.

Farm fires in Punjab surged to their highest levels this season, prompting experts to sound warnings of severe air pollution in the Capital in the coming week even though there was a slight respite on Wednesday, and sparking a political war of words over the annual crisis.

Heavy smog has been deteriorating the city’s air quality, as seen here early morning at Majlis Park in New Delhi, India, on Wednesday, November 2, 2022. (HT Photos)
Heavy smog has been deteriorating the city’s air quality, as seen here early morning at Majlis Park in New Delhi, India, on Wednesday, November 2, 2022. (HT Photos)

On Tuesday, the 24-hour average air quality index (AQI) was 376, according to the Central Pollution Control Board’s (CPCB) 4pm bulletin. The reading was an improvement over the 424 recorded the day before, when air pollution was in the worst “severe” band before relenting to “very poor”, helped largely by an increase in local winds.

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But by late evening on Wednesday, the AQI began to inch up again, reaching 389 by 9pm. “Wind direction which was westerly and even southeasterly on Tuesday, once again switched to northwesterly on Wednesday and started to bring stubble emissions towards Delhi. However, local winds were between 6 to 20 km/hr during the day and pollutants were able to disperse freely,” said VK Soni, scientist at the India Meteorological Department (IMD) and a member of the Commission for Air Quality Management (CAQM).

But, he added, worse is in store, both due to the surge in farm fires and in weather conditions that are predicted to develop.

Also read: Delhi govt bans construction work, blames UP diesel buses for pollution

“During a change in wind direction or transition, wind speed may reduce slightly. The other variable is also the fire count and how much it rises. The count has doubled in the last 24 hours and if the rise is significant, then these forecasts may not remain as accurate,” he said.

Overall, 4,172 fires were spotted from satellites over north India, with Punjab accounting for 3,634, or 87% of these — a sharp rise from 1,842 a day ago. Haryana recorded 166 fires, up from 88 on Tuesday.

The crisis triggered a political spat between the Delhi chief minister Arvind Kejriwal and the Union government. Kejriwal on Wednesday tweeted and asked people to not do politics around air pollution, saying the problem was not limited to one state alone.

“Don’t do politics with pollution. Pollution is not only in Delhi and Punjab, it is in the whole of north India. Don’t abuse farmers and don’t file an FIR on them. The people of Punjab and Delhi are taking all steps at their level. The Centre will have to come forward and work out a solution with all the state governments,” said Kejriwal, whose Aam Aadmi Party is also in power in Punjab.

Union environment minister Bhupender Yadav also took to social media, stating the trend in farm fires so far was clear.

“Sample this: As of today, Punjab, a state run by the AAP government, has seen an over 19% rise in farm fires over 2021. Haryana has seen a 30.6% drop. Just today, Punjab saw 3,634 fires. There is no doubt over who has turned Delhi into a gas chamber,” he tweeted.

Hiren Jethva, aerosol and remote sensing scientist at US’s Morgan State University and National Aeronautics and Space Administration (Nasa) Goddard Space Flight Centre, said that the aggregated crop fires count in Punjab and Haryana is now following the 2021 curve but peak burning period is yet to arrive.

“PM2.5 (particulate matter with diameter less than 2.5 micrometres) in Delhi is affected by fires in Punjab and Haryana through low-level transport, possibly descending air mass, and semi-direct effect of smoke — an elevated heating increases atmospheric stability, suppresses vertical mixing, which in turn makes it difficult to disperse smoke,” he said via an email exchange.

In other words, the city is — as it is often this time of the year — trapped in the perfect storm of factors. Meteorologically, the pre-winter conditions mean colder, heavier air descends, bringing in the smoke from farm fires in Punjab and Haryana that have travelled through high-level transport winds.

Also read: AAP govt launches revamped ‘One Delhi’ app for public transport

The layer of haze then stops the sunlight from penetrating and heating up the lower altitudes while two blankets of air form -- one closer to the ground, cold hazy and thick with pollution, and the higher up, warmed by the sun’s rays. This separation, also known as the inversion effect, limits the vertical headroom for pollutants even from local emissions to be dispersed in the blanket of haze closer to the ground.

Other experts said that, just like every year, these conditions will combine with the effect from farm fires, which too reach a peak in the first half of November. “In the last few years, we have seen a peak of farm fire cases in the first and second week of November. If wind direction is northwesterly, which it is at present, the impact can be significant. Temperatures are also dropping at the moment and AQI could worsen in the next few days, particularly on Thursday, if farm fire count is high again,” said Anumita Roychowdhury, executive director, research and advocacy at the Centre for Science and Environment (CSE).

Dipankar Saha, former head of Central Pollution Control Board’s air laboratory, too said November brings Delhi’s most polluted season. “While Diwali was early this year, stubble peaks lead to a significantly high contribution to Delhi’s PM 2.5. With the peak expected in the coming days, we may see air quality worsen again,” he said.

In large parts of Punjab, harvesting of paddy has been completed, causing an upward trajectory in farm fires. A thick layer of smog has also enveloped Punjab, where 3,634 cases of fire were recorded on Tuesday, according to the state’s remote sensing experts.

The number for Tuesday is the highest in a day for this season.

Bharatiya Kisan Union, Dakounda, general secretary, Jagmohan Singh said that the government, particularly in the Centre, should find a long-term solution to tackle the problem of farm fires. “Now when we are in middle of the crisis, it’s of no use. A long term action plan is required with adequate funds support to deal with the problem of paddy stubble burning”, he said, adding that farmers do not want to set the crop waste on fire but they are left with no other means.

According to projections, the share of farm fires in Delhi’s air lay close to 12%. The System of Air Quality and Weather Forecasting And Research (Safar), said farm fires contributed 12.5% of the pollution in Delhi’s air on Wednesday, dropping from 14% the day before. The body attributed the improvement to wind speeds at the transport level.

The Decision Support System, a tool developed by the Ministry of earth sciences and the Indian Institute of Tropical Meteorology (IITM), meanwhile said the contribution of farm fires peaked at around 10% on Wednesday, with an average contribution of around 7.5%.

Urban Emissions, a platform to analyse air pollution across the country, also estimated the contribution of stubble burning or open fires to Delhi’s PM 2.5 to be 12.5% on Wednesday. It forecasts this to rise to 27% by Thursday.

On Wednesday, CAQM in NCR also held a review meeting with the states of Haryana, Rajasthan and Uttar Pradesh, asking them to ensure stringent action under the three stages of the Graded Response Action Plan (Grap) already in place. It said those not following norms should also be penalised heavily.

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