Scientists at the NASA Goddard Space Flight Center in Maryland, US, may have a new tool to offer weathermen - a way to predict a bad hurricane season.
Hurricanes are "born" in the Caribbean and western Atlantic when high sea temperatures warm the overlying air sufficiently and trigger strong winds as the hot air starts to rise. But researchers William Lau and Kyu-Myong Kim wondered whether the 200 million tonnes of sand and dust blown every year into the atmosphere from the Sahara desert could have a shielding effect, cutting down the amount of sunlight hitting the sea and therefore reducing ocean temperatures and the numbers of hurricanes.
To find out they compared satellite images of dust clouds from the Sahara with sea temperatures in the summers of 2005 and 2006. In 2006 the sea temperatures were lower, no hurricanes hit the land that year, and sure enough there was a larger than average dust cloud. The effect is most marked in summer, between June and August. Before then the dust is too scarce in the atmosphere to make much difference.
The research, which is published in the journal Geophysical Research Letters, could help forecasters to predict future storms with greater accuracy. Indeed, a Colorado State University-based team that produces quarterly hurricane predictions plans to include Saharan dust figures in their weather models in future. According to the group leader Phil Klotzbach, "the dust information will be quite useful for our final seasonal forecast in August."
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