37 flights diverted as Delhi faces severe toxic haze

A rare weather phenomenon that accelerated spawning of tiny polluting particles led to blanketing of the national capital and its satellite cities on Sunday with a thick toxic haze that not only triggered itching of the eyes even inside the houses but also led to the diversion of 37 flights which could not land because of poor visibility.

The climatic change – common in late December and January, but rare in early November – was triggered by the Saturday evening drizzle that brought a temporary sense of relief to a section of the residents of Delhi national capital region.

But they woke up to a choking Sunday as pollutants enter the houses causing itching and constant irritation of the eyes. Those who had breathing troubles had a tough time.

According to the Ministry of Earth Science's SAFAR air quality monitoring system, Delhi had an air quality index of 625 while Noida is 667 and Gurugram stands at 737. In the SAFAR system, an AQI of 400-500 is “severe” and anything beyond that is “severe plus.”

The Central Pollution Control Board records Delhi's AQI at 494 at 4 PM while that of Noida and Gurugram are 495 and 486 respectively. In the CPCB scale, an AQI of 400-500 means the air quality is “severely” bad and the scale ends at 500.

Such poor quality of air, explained a SAFAR official, was due to “secondary particulate formation”, a mechanism when PM-2.5 starts to multiply rapidly. Last night's rain acted as a catalyst by increasing the holding capacity of the air and in the absence of solar radiation, the boundary layer continues to be very low (50-100 mt), arresting pollutants during the daytime.

“Under this process, bigger particles like PM-10 and several others are getting converted to smaller particles like PM-2.5 whose share in the pollutant mix is now above 75% (normal is 50%). Because of the congenial weather conditions, the secondary aerosol formation has expanded manifold,” Gufran Beig, project director of SAFAR and a scientist at Indian Institute of Tropical Meteorology at Pune told DH.

While there are some clouds above Delhi, weather scientists do not foresee a rainfall to get the relief. There is a decline in the stubble burning as it contributed to 17% of the pollution on Sunday compared to 44% on Friday.

An increase in the wind speed may be likely around Tuesday to disperse a part of the haze, but the Monday in all probability would be as gloomy and polluted as Sunday.

The season's heaviest pollution haze caused a major disruption at Delhi airport as 37 flights were diverted to Jaipur, Amritsar Lucknow and Mumbai, airport officials said.