The US is always looking for ways of improving its seasonal hurricane forecasts and Amato Evan reckons he can help. He is testing a new forecasting tool, and the critical element is dust.
Every year, large amounts of Saharan dust are blown off the West African coast and over the North Atlantic. There, they are thought to reflect solar radiation back out into space, cooling the temperature of the surface of the ocean.
Given that the North Atlantic is the breeding ground for hurricanes that make landfall in the US and that their formation is triggered by warm sea-surface temperatures, Evan believes studying desert dust could improve the forecasts put out at the beginning of the hurricane season each May.
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Evan and his colleagues calculated the dust鈥檚 influence on sea-surface temperatures and hurricane strength by combining 25 years of satellite data showing the amount of dust suspended in the atmosphere with a conventional climate model. They estimate that about one-third of the increase in hurricanes intensity over the last 25 years is due to decreases in atmospheric dust load.
Evan has extended his research to produce a dust-forecasting tool that uses precipitation patterns over Africa during the previous year to estimate how much dust will be released by the Sahara during the coming the summer.
Evan predicts a moderate amount of dust for 2008. 鈥淲e have a computer model that takes the dust forecast and tries to estimate how much that dust storm activity will cool the ocean,鈥� he says. His computer forecasting tool calculates that dust will cool the Atlantic by about 1.1掳C during the 2008 hurricane season, which is close to the average during the past 27 years.
鈥淭here is not likely to be an anomalously large warming or cooling [of ocean temperatures] due to dust storms,鈥� he says.
Gerry Bell, lead seasonal hurricane forecaster for the US National Oceanic and Atmospheric Administration, admits that atmospheric dust is not a key element in current forecasts. 鈥淭here are more dominant factors, like El Ni帽o and La Ni帽a events,鈥� he told 快猫短视频.
However, he says that his colleagues at NOAA鈥檚 base in Miami, who predict hurricane tracks five days ahead throughout the season, do consider atmosphere鈥檚 dust load. Among other things, the NOAA meteorologists see dust clouds as a sign of very dry air, which is not conducive to hurricane formation. 鈥淒ust 鈥� and dry air 鈥� kills hurricanes,鈥� says Bell.
Journal reference: (DOI:10.1029/2007GC001774)
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