Haze returns to Delhi; change in weather pattern to blame

It's fog, not smog, say experts; to continue for 3 more days

Haze returns to Delhi; change in weather pattern to blame

A thick blanket of pollution - caused by a change in weather pattern - returned to the national capital on Monday.

The Central Pollution Control Board's air quality index for Delhi and its three satellite towns - Noida, Gurugram and Faridabad - was in the "very poor" category while Ghaziabad was in the "severe" category.

The main culprit was particulate matters (PM-2.5 and PM-10), whose levels were 5-6 times above the CPCB safe standards and 12-15 times higher than the World Health Organisation's limits in most of the pollution measurement stations.

"This was caused by a change in the mixing height of pollutants. It was nearly 2000 mt in the last few days, but came down to nearly 1700-1800 metres on Sunday and is likely to stay like that for the next 48 hours," K J Ramesh, director general of India Meteorological Department told DH.

Mixing height is the height of vertical mixing of air and suspended particles that cause pollution. During the pollution-crisis days, the mixing height came down to 200 metres, but with the change of weather, the situation improved in Delhi.

A drop in temperature leading to moderate fog in Punjab, Haryana and Delhi brought down the visibility and compounded the scenario.


After last month's pollution emergency, the authorities took several steps like closure of schools, stopping all construction work and banning the entry of trucks unless they were carrying essential commodities. While emergency measures were lifted, there are still restrictions on the use of diesel generators.

"Now there is no stubble burning. The pollution sources are locals like construction dust and transport," Ramesh said.

"It's more of a local weather phenomenon that comes with winter. It's more of a fog, rather than smog and likely to continue for the next three days. This is different from last month's situation when there were external sources like dust storm and stubble burning," said Gufran Beig, who heads the Ministry of Earth Science's pollution monitoring wing named System of Air Quality and Weather Forecasting and Research (SAFAR-India).

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