‘Calm’ winds spike pollution levels in Delhi

Delhiites breathed in “severe” levels of pollution on Monday, the first full working day since the Delhi government’s car-rationing experiment started on January 1.

In fact, the level of the harmful PM2.5 (particles below or 2.5 microns in size) spiked by about 18 per cent over the course of the day. According to the System of Air Quality and Weather Forecasting and Research (SAFAR) index of the Union Earth Science Ministry, the average PM2.5 level from eight monitoring stations rose from 226 at 8 a.m. to 266 micrograms per cubic metre at 7 p.m. This meant that the air quality index (AQI) was over 400, putting pollution in the “severe” category.

“The increase in PM2.5 levels is associated with prevailing weather conditions,” said SAFAR project director Gufran Beig, referring to the relatively calm winds and high moisture levels seen on Monday.

According to a Meteorological Department official, the minimum temperature remained at 8 degrees Celsius, the same as Sunday.

Moisture levels high

The maximum rose from 22.8 degrees Celsius on Sunday to 23.2 degrees on Monday, four degrees above normal for this time of year. Since the wind speed fell to “calm” levels on Monday, pollutants did not get swept away as they did on Sunday, when westerly winds were observed. The moisture levels also remained high, between 97 to 53 per cent,

Anumita Roychowdhury, the head of the Centre for Science and Environment’s clean air campaign, said climatic conditions will only lead to higher pollution levels over the coming weeks. “As the weather gets colder in January, pollution levels increase. We have to take that into account when we assess the impact of the odd-even policy,” said Ms. Roychowdhury.

Citing the Delhi government’s data for Day One of the odd-even experiment, she added that the dip in PM levels, that happens everyday from early morning to afternoon, was more pronounced compared to previous days, pointing towards the effect of the policy.


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