Delhi air pollution spikes again, rain forecast holds out hope

The air quality index shot up from 305 to 377 on a scale of 0- 500 on Sunday as the landlocked city was caught in the crosswinds of a depression over the Bay of Bengal and a western disturbance blowing from the Mediterranean region.

Air pollution in the national capital spiked on Sunday as two weather patterns that surfaced thousands of kilometres away pushed up the level of airborne pollutants in the city.

A cyclist wearing a mask rides on his vehicle amid heavy smog in New Delhi on December 5, 2017 (AFP)

India’s official pollution forecasting system SAFAR has forecast the air quality to dip more on Monday.

But the weather office predicted light rain on Monday night and Tuesday. Winter rain may bring the Celsius down but will also help wash away pollutants, giving Delhi a breath of fresh air.

The air quality index shot up from 305 to 377 on a scale of 0- 500 on Sunday as the landlocked city was caught in the crosswinds of a depression over the Bay of Bengal and a western disturbance blowing from the Mediterranean region.

This is the third time in a month that weather disturbances caused Delhi’s air quality to deteriorate. The other two turbulences were cyclone Ockhi over the Arabian Sea early December and a dust storm barreling down from West Asia in the first half of November.

The Bay of Bengal depression has obstructed a strong northwesterly wind that was blowing last week over Delhi and flushing out pollutants.

The wind, moving without hindrances, and light rain on Wednesday night improved the city’s air quality and the AQI dropped to 194 the next day. This helped Delhi record “moderate” pollution in December for the first time in two years.

“But the depression over the Bay of Bengal has blocked this clear passage. The cross-ventilation got disrupted and the wind speed dropped from around 15kmph on Thursday to around 5kmph on Sunday,” said a senior official with the Indian meteorological department.

“The wind failed to disperse pollutants and the air quality started deteriorating,” he said.

Data collated by the Central Pollution Control Board (CPCB) say the city’s air quality has been deteriorating over the past three days and the level of particulate matter — PM10 and PM2.5 — has more than doubled.

The level of fine dust particle PM10 and PM2.5, which is even finer and more hazardous for people, is now four times above the safe standard of 100 and 60, respectively.

“This is mainly because of disturbances in the weather,” said D Saha, who heads the CPCB’s air quality laboratory.

A western disturbance, or storms originating over the Mediterranean, is adding to the problem.

“This has pushed up moisture levels. The result is that Delhi is witnessing misty mornings. This disturbance has helped trigger a cyclonic circulation over Rajasthan. There could be some rain on Monday night and Tuesday,” said Kuldeep Srivastava, a senior scientist with Delhi’s weather office.

Pollutants are getting trapped because of the low wind speed and high moisture level. The cyclonic circulation is acting like a trap for pollutants in Delhi and its satellite cities.