Smog warning: Worst is yet to come

207 HRS and Counting Met warns of dense smog starting Nov 12, says not seen since 1989

After 207 hours of smog cover, the city saw clear sky when the afternoon sun returned on Thursday. But the worst of the fog spell, which leads to smog formation, is yet to come, the weatherman claims.

The maximum total fog hours in November was in 2008, when there were three spells of fog totalling 245 hours for the month.

This year, the month is already close to the previous high with three weeks to spare.

"November is usually when the fog starts to collect. In November 2008, Delhi had three spells of 5-11 days of smog. In total, it lasted for 245 hours," said R K Jenamani, Director of IGI Met department.

He claimed this month could be the worst since 1989 when fog data was analysed for the first time.

Scientists say the average fog duration for a day has already increased by eight hours since 1989.

The forecast warns of the return of fog around November 11 when wind speed is likely to slacken.

The recent smog spell was attributed to the aftereffects of Cyclone Nilam which struck the Tamil Nadu coast on November 1. Scientists say moisture in the air over Delhi stayed until Wednesday, pushing up relative humidity level to 75 to 95 per cent. Lack of wind meant that pollutants were not swept away, causing the smog to intensify.

Through last week, air pollution level was recorded 8 to 10 times higher than the national standard. The Respirable Suspended Particulate Matter level at Anand Vihar was 1,559 ug/m3 — 15 times more than the national standard of 100 ug/m3. At RK Puram, it was 836 ug/m3.

The Met department says the relief from fog came due to a three-fold jump in the speed of surface wind from 0-5 kmph on Wednesday to 16 kmph on Thursday. General wind speed improved from 5-10 kmph on Wednesday to 25 kmph on Thursday. Visibility at IGI Airport improved to 2,500 metres on Thursday.

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