African Dust May Mute Atlantic Hurricanes

MADISON, Wisconsin, October 11, 2006 (ENS) - Dust from the Sahara Desert may help reduce the intensity of Atlantic hurricanes, according to new research by U.S. scientists. The study found less hurricane activity in years when stronger dust storms rose from the Sahara Desert and blew off Africa's western coast and more intense hurricanes in years when dust was relatively scarce.

"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 Madison at Wisconsin. "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."

The researchers said that if they can conclusively prove that dust storms help to squelch hurricanes, weather forecasters could one day begin to track atmospheric dust, factoring it into their predictions for the first time.

The study was published Tuesday in the journal "Geophysical Research Letters."

Last year's Hurricane Wilma was the most intense hurricane ever recorded in the Atlantic basin. (Photo courtesy NASA)

The research team analyzed 25 years of satellite data - dating from 1981 to 2006 - and noticed the correlation. The study reflects increasing attention to the environmental impact of dust. In some years, many million tons of sand rise up from the Sahara Desert and float right across the Atlantic Ocean, sometimes in as few as five days.

"People didn't understand the potential impact of dust until satellites allowed us to see how incredibly expansive these dust storms can be," said lead author Amato Evan, a researcher at UW-Madison's Cooperative Institute for Meteorological Satellite Studies (CIMSS). "Sometimes during the summer, sunsets in Puerto Rico are beautiful because of all the dust in the sky. Well, that dust comes all the way from Africa."

The dust rises when hot desert air collides with the cooler, dryer air of the Sahel region, just south of the Sahara, and forms wind.

As particles swirl upwards, strong trade winds begin to blow them west into the northern Atlantic. Dust storms form primarily during summer and winter months, but in some years - for reasons that aren't understood - they barely form at all.

The findings of the study make sense, the researchers said, because dry, dust-ridden layers of air probably helps to "dampen" brewing hurricanes, which need heat and moisture to fuel them.

That effect, explained coauthor and CIMSS research scientist Christopher Velden, could also mean that dust storms have the potential to shift a hurricane's direction further to the west, which unfortunately means it would have a higher chance of hitting the United States.

The research team said the work doesn't confirm that dust storms directly influence hurricanes, but it does provide compelling evidence that the two phenomena are linked in some way.

"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," Foley said. "That's what future research needs to find out."