After many years of studying links between hurricanes and warming ocean currents, scientists at the University of Wisconsin in Madison have come up with a surprising new correlation. They have begun to notice a pattern that in years when Sahara winds swirl with heavy dust, fewer hurricanes sweep through the Atlantic. Venturing carefully into the risky world of weather prediction, the Wisconsin researchers suggest that during many hurricane seasons, dust storms circulating westward out of Africa’s Sahara Desert may help suppress the development of hurricanes in the tropical North Atlantic. Amato Evan of Madison’s Cooperative Institute for Meteorological Satellite Studies explains the thinking behind the latest findings to VOA English to Africa reporter Howard Lesser.
“When we have these dust storms, we’re basically moving the air that’s over Africa over the North Atlantic. So for any storm to grow when it hits all of this dry air, it really just shuts down the convection and the storm isn’t able to intensify. Basically, the dust tends to absorb radiation like a warm blanket in the middle of the atmosphere, which you might refer to as an inversion. Generally, inversions are associated with a very stable environment which doesn’t promote storm growth,” he said.
As lead author of findings published this week in the journal Geophysical Research Letters, Amato Evan, says that West African dust storms play as crucial a role as ocean currents in determining whether hurricanes and tropical depressions can survive.
“The correlations between dust and hurricanes were almost equally as important as the correlations with the hurricanes and the sea surface temperature. And basically, what we saw was the sea surface temperature changes were kind of this slower, long-term growth in the hurricane numbers, whereas the dust activities seem to be more well correlated with the year-to-year ups and downs that we see in tropical cyclone numbers,” he said.
Evan says scientists are turning their attention to studying the environmental impact of dust in Africa after monitoring 25 years of satellite data. The findings show that several different factors are responsible for the long-term patterns of hurricane formation.
“We definitely saw a big increase in dust levels during the early 1980’s. They dropped down again in the late ‘90’s and now they look like they are picking up again, which is a little bit contrary, because I know that the last few years, they haven’t necessarily been particularly dry years in West Africa," he said.
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