Sahara dust may lower Atlantic hurricane frequency: study

A surprising link may lie between the frequency of Atlantic hurricanes and thick clouds of dust that periodically rise from the Sahara Desert, U.S. scientists reported on Tuesday.

During periods of intense Atlantic hurricane activity, dust was relatively scarce in the Sahara atmosphere, while in years when stronger Sahara dust storms rose up, fewer hurricanes swept through the Atlantic, according to a report filed in the Oct. 10 issue of the journal Geophysical Research Letters.

Scientists at the University of Wisconsin-Madison put forward the intriguing theory after poring over satellite data from 1981 to 2006.

The Sahara sand rises when hot desert air collides with the cooler, drier air of the southern region 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 they barely form at all.

According to the researchers, the dry, dust-ridden layers of air probably helps to "dampen" brewing hurricanes, which need heat and moisture to fuel them. That effect 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.

"People didn't understand the potential impact of dust until satellites allowed us to see how incredibly expansive these dust storms can be," said Amato Evan, a researcher at the University of Wisconsin who led the study.

"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," he said.

Researchers have increasingly turned their attention to the environmental impact of dust, after it became clear that 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.

The findings show that long-term changes in Atlantic hurricanes may be related to not only the warming ocean temperatures, but also many different factors such as the dust wind, the researchers said.

While the new study work doesn't confirm that dust storms directly influence hurricanes, 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 are responding to the same large scale atmospheric changes around the tropical Atlantic," said study co-author Jonathan Foley.

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

If further studies 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, according to the researchers.

Source: Xinhua