Dust storm in West Asia precipitated smog crisis'

New Delhi: A large multi-day dust storm, which emerged in Iraq, Kuwait, and Saudi Arabia in October, was the main contributor to the recent smog episode in Delhi-NCR, said an analysis by Safar, a Centre-run agency. The pollution contribution of the Gulf dust storm on peak day (November 8) was around 40 per cent and that of stubble burning was 25 per cent, said Safar (System of Air Quality and Weather Forecasting and Research).

According to the Safar assessment report of the week-long pollution crisis, November 8 was the day when pollution levels peaked with PM 2.5 concentrations reaching 640 micrograms per cubic metre (µg/m3).

There was large multi-day dust storm that emerged in Iraq, Kuwait, and Saudi Arabia in the last week of October that continued upto November 3-4. This dust storm was carried by relatively cool winds, said Safar, adding that as air temperature dropped, winds and dust was likely to slowly diminish. However, by that time it reached the upper part of the atmosphere (1.5- 3 km, 700-850 hPa) where winds became very strong (15-20 kmph) and its direction changed towards India (westerly, north-westerly). The change in direction of the dust storm was what affected a large region of NCR, including Delhi.

The imposition of emergency measures, such as ban on the entry of trucks and construction activities, yielded positive results, thereafter putting the gains at around 15 per cent in terms of percentage, the agency said.