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Giant sandstorm shrouds Atlantic

Jan 1, 2003

A giant sandstorm roughly the size of Spain made its way across the Atlantic in February while being tracked by NASA satellites. The storm, originating in the Sahara Desert, resulted from a combination of high winds and warm, rising air, and tracked seaward while covering hundreds of thousands of square miles.

The storm was first observed by members of NASA's Sea Viewing Wide Field-of-View Sensor (SeaWiFS) project on Feb. 26. Satellite images showed a massive band of brown cloud cover extending from the Moroccan coast of the Sahara roughly 1,000 miles into the Atlantic and moving west-northwest at about 50 kph. "The storm we saw on the 26th was really dense, really big, and really concentrated," said Gene Feldman, an oceanographer at SeaWiFS. While a portion of the storm broke off for Portugal and Spain on the 28th, the central Atlantic remained smothered. "From about 20° N to 10° S, from the coast of Africa to the coast of Brazil, is still blanketed," said Feldman in an interview in mid-March.

While its magnitude was unusual, its occurrence was not. Dozens of such storms are believed to form annually. Their effects appear to be as far-reaching as the Caribbean, particularly in summer months when warmer air allows the sand to rise to heights of 15,000 feet and thus travel greater distances. Dust particles known to have originated in the Sahara have been found on Caribbean islands and on certain coral. The U.S. Geological Survey is even studying whether sand is a significant contributing factor in reef deterioration. The deposit of a fungi in the dust onto the reefs is believed to cause a chemical reaction with the coral and initiate its deterioration, according to reports from USGS scientists. Such westward-tracking sandstorms are also believed to influence hurricanes by providing atmospheric energy necessary to maintain their force.

While Feldman had never been at sea in the middle of a sandstorm, he speculated that it could be problematic in terms of both visibility and equipment. "We got reports from guys on the Canaries that visibility was way downto a couple of hundred meters." Any equipment on deck would be subject to potential problems, he said. "If you have any kind of sensitive equipment, or ones with exposed bearings, it could cause all sorts of problems. Any kind of optical gear you'd want to keep covered," he said. "I would think air filters would get clogged, too. It tends to cover stuff with a fine grit. And, it'll screw up SST map retrievals because the storm blocks the view."

The SeaWiFS project is a component of NASA's Mission to Planet Earth program, an ongoing effort to understand the earth's behavior by observing it from space. The image was part of a series that tracked the storm and were posted on the SeaWiFS web site, which routinely runs weather images from around the world: http://seawifs.gsfc.gov.

Christopher Baker