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Last Updated: Tuesday, 10 October 2006, 17:03 GMT 18:03 UK
Dust 'affects hurricane activity'
Satellite image of a hurricane  Image: Eumetsat
Several factors may influence the development of hurricanes
US researchers have discovered a link between Atlantic hurricane activity and thick clouds of dust that periodically rise up from the Sahara Desert.

At times of intense hurricane activity, dust clouds were scarce, but in years with stronger dust storms, fewer hurricanes swept across the Atlantic.

The work raises the tantalising possibility that Saharan dust storms could help to quench hurricanes.

Details appear in the scientific journal Geophysical Research Letters.

"These findings are important because they show that long-term changes in hurricanes may be related to many different factors," said co-author Jonathan Foley, director of the Center for Sustainability and the Global Environment at the University of Wisconsin-Madison.

"While a great deal of work has focused on the links between [hurricanes] and warming ocean temperatures, this research adds another piece to the puzzle."

Dust tracking

Researchers have increasingly turned their attention to the environmental impact of dust, after it became clear that, in some years, millions of tonnes of sand rise up from the Sahara Desert and travel across the Atlantic Ocean - sometimes in as little as five days.

If scientists conclusively prove that dust storms help to suppress the development of hurricanes, weather forecasters could one day begin to track atmospheric dust, factoring it into their predictions for the first time, the researchers say.

Infographic, BBC

The Saharan sand rises when hot desert air collides with the cooler, drier air of the Sahel region, just south of the Sahara.

The windy conditions that result toss the sand upwards. Then, strong trade winds begin to blow them westward into the northern Atlantic Ocean.

Dust storms form primarily during summer and winter months, but in some years, for reasons that are not understood, they barely form at all.

The researchers say that dry, dust-ridden layers of air probably help to "dampen" brewing hurricanes, which need heat and moisture to fuel them.

But co-author Christopher Velden, from the University of Wisconsin-Madison, said that effect could also mean that dust storms had the potential to shift a hurricane's direction further to the west, which means it would have a higher chance of hitting the United States and Caribbean islands.

"What we don't know is whether the dust affects the hurricanes directly, or whether both [dust and hurricanes] are responding to the same large-scale atmospheric changes around the tropical Atlantic," said Dr Foley. "That's what future research needs to find out."

The study was funded by the US National Oceanic and Atmospheric Administration (Noaa).


SEE ALSO
Humans 'causing stronger storms'
11 Sep 06 |  Science/Nature
'Above normal' hurricanes in 2006
22 May 06 |  Science/Nature
Hurricanes and global warming - a link?
23 Sep 05 |  Science/Nature

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