Tracking atmospheric dust for predicting hurricanes
weather forecasters will now need to track atmospheric dust to predict hurricanes. Dust may dampen hurricane fury, say scientists at the University of Wisconsin-Madison, studying a link between Atlantic hurricanes and thick clouds of dust that periodically rise from the Sahara Desert and blow off Africa's western coast.
A strong relationship between variations in North Atlantic tropical cyclone activity and atmospheric dust cover as measured by satellite, from 1981 to 2005, has been demonstrated in the study published in Geophysical Research Letters (Vol 33, No 21).
While the study does not demonstrate a direct causal relationship, there appears to be a link between tropical cyclonic activity and dust transport over the Tropical Atlantic."What we do not know is whether dust affects hurricanes directly, or whether both are responding to the same large-scale atmospheric changes around the tropical Atlantic,' says lead author Amato Evan.
From the satellite data, Evan made the observation that during intense hurricane activity, dust was relatively scarce in the atmosphere. In years when there were stronger dust storms, fewer hurricanes swept through the Atlantic.
"These findings are important because they show that long-term changes in hurricanes may be related to many different factors,' says Jonathan Foley, co-author and director of Madison's Center for Sustainability and the Global Environment. "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. If scientists 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,' he adds.
Researchers have increasingly focused on the environmental impact of dust, after it became clear that in some years many million tonnes of sand would rise up from the Sahara Desert and float right across the Atlantic Ocean, sometimes in as few as five days.
The Sahara sand rises when hot desert air collides with the cooler, dryer air of the Sahel region, south of Sahara, and forms wind. As particles swirl upwards, strong trade winds blow them west into the northern Atlantic. Dust storms form usually during summer and winter months, but in some years they barely form at all. Scientists have not been able to crack the reason so far.
Researchers say that dry, dust-ridden layers of air helps "dampen' brewing hurricanes, which need heat and moisture to fuel them. That effect, scientist Christopher Velden adds, could mean that dust storms may shift a hurricane's direction further to the west. ?