A lethal cocktail of air-borne pollutants that has engulfed large parts of northern India and Pakistan is likely to clear up only by the weekend.
“We expect this [weather system] to dissipate from November 10 onwards, following which there will be a relief from the smog,” said M Mohapatra, scientist at the National Weather Forecasting Centre of the India Meteorological Department.
An anticyclonic circulation has developed over areas including New Delhi, Haryana, Punjab and Uttarakhand, Mohapatra explained.
Anticyclonic circulations of air move clockwise around a central region of high pressure in the northern hemisphere. This means that while winds are moving around the periphery of the region, air in the centre remains trapped. This weighs down low-lying pollutants in that area.
Dipankar Saha, a scientist at the Central Pollution Control Board who is monitoring the situation said that this was an “accumulation phase” where there was no chance of dispersion of pollutants because there is no entry of air from outside the circulation area.
“That is why the pollution is increasing day by day,” Saha said. He added that this was not smog. “It is particulate matter and ash in the air.”
An air quality index data for Delhi showed that particulate matter of 10 micrometres, or PM10 had hit 999 in Punjabi Bagh and RK Puram in New Delhi. The lowest reading of PM10 for the National Capital Region was 330 in Gurugram, while other areas in the region ranged between 420 and 700. The Central Pollution Control Board classifies a reading of 100 as “satisfactory”. Last year, index readings touched 500 after Diwali.
The gas chamber-like phenomenon has led to car crashes on the Yamuna Expressway, Delhi’s schools to be shut until Sunday and a public health emergency to be declared in the capital region.
Though the condition developed in conditions favourable to fogs, which are common in northern India at this time of the year, Mohapatra was at pains to clarify that the current situation is no mere fog.
“Fog occurs when there is humidity in the air and so appears in the morning hours,” he said. “However, today in Delhi, the condition was more intense in the afternoon, at which time there is usually is no fog. So weather is not the only factor.”
While Delhi has a dense collection of meter readings, the extent of the pollution is not limited just to the National Capital Region, as this map of particulate matter 2.5 across the subcontinent shows. Even parts of Pakistan along the River Indus and almost the entire Gangetic plain is highly polluted.
While the circulation is likely to dissipate over the weekend, this does not reduce the severity of pollution that has led to it in the first place. These sources included crop burning and industrial emissions in northern India.
Saha expressed his helplessness at the present situation. He said, “We can cut down on ground pollution, but we cannot dilute or churn the air.”