Pollution from soot and aerosol emissions may be to blame for the increased destructive power of cyclones in the Middle East and South Asia, according to a recent study.
Unlike tornadoes, which usually form over land and move quickly along narrow paths of destruction, cyclones are known for developing over water, and can last for hours or even days.
Traditionally, prevailing wind-shear patterns prevent cyclones in the Arabian Sea from becoming major storms. A paper appearing in the Nov. 3 issue of the journal Nature, however, suggests the weakening of the winds aloft has enabled the formation of stronger cyclones in recent years – including storms in 2007 and 2010 that were the first recorded storms ever to enter the Gulf of Oman.
Scientists behind the study say pollution from sources such as biomass burning and diesel vehicles have interfered with natural wind patterns, reducing wind shear and enabling cyclones to grow twice as intense.
To reach this conclusion, researchers compared cyclones that occurred between 1979 and 1996 with those between 1997 and 2010. It is known that during the last several decades, anthropogenic emissions of aerosols have increased sixfold, creating a thick layer of pollution over the Indian Ocean, known as the South Asian atmospheric brown cloud.
The research team discovered that cyclones developing during this period of increased air pollution were up to three times more intense, with higher wind speeds — and five of the strongest storms during the period occurred after 1998.
“We are showing that pollution from human activity – as simple as burning wood or driving a vehicle with a diesel engine – can actually change these massive atmospheric phenomena in a significant way,” said Amato Evan, lead author of the study and a researcher at the University of Virginia. “It underscores the importance of getting a handle on emissions in the region.”
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