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12 March 2004
Amateur meteorologists photograph massive African dust storm
by Forrest M. Mims III
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This
satellite image shows a massive plume of Sahara dust being blown
over the Atlantic Ocean on 4 March 2004. The plume dropped significant
amounts of dust on the Canary Islands just off the African coast
in the upper part of the image. The Cape Verde Islands are off the
coast of Africa at bottom. The image is by the MODIS instrument
aboard NASA's Terra satellite. See http://rapidfire.sci.gsfc.nasa.gov/ |
Every year windstorms across the Sahara Desert blow hundreds of millions of tons of dust high into the sky over North Africa. Depending on the season, the dust may be blown across the Mediterranean Sea into Europe or over the Atlantic Ocean. The dust often reaches the Western Hemisphere, where it fertilizes bromeliads in Brazil, dirties windshields across the Southeastern United States and causes brilliant red sunsets across the American Southwest.
The Canary Islands and the Cape Verde Islands just off the western coast of North Africa often receive considerable dust from these events. On 3-4 March 2004, an unusually massive storm formed a huge arc of thick dust that swept over the Canary Islands. This event was captured by various satellites, including NASA's Terra and Aqua.
Dr. Xavier Calbet, a meteorological scientist with EUMETSAT in Darmstadt , Germany, is among the European scientists who follow Saharan dust events. He e-mailed to Dr. Joseph Prospero, a pioneer in Sahara dust studies, several spectacular photographs made by amateur meteorologists Eugenio Rodriguez and Sergio Suarez as the dust event crossed Tenerife in the Canary Islands.
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Amateur meteorologist Eugenio Rodriguez photographed a blanket of thick Sahara dust invading Tenerife, Canary Islands, on or about 3 March 2004. See Foro Canariasmet at http://meteo.viajesinsular.es. Click image to enlarge. |
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Amateur meteorologist Eugenio Rodriguez photographed still more Sahara dust invading Tenerife, Canary Islands, on or about 3 March 2004. See Foro Canariasmet at http://meteo.viajesinsular.es. Click image to enlarge. |
Dr. Calbet concluded from the photographs made by Rodriguez that the top of the dust cloud dust was below around 2,500 meters, and that the sky was clear above the dust. He described this as a typical winter dust outbreak over the Canary Islands. However, he noted, the intensity of the dust was greater than normal.
The photographs by Rodriguez were made from near the top of the dust layer. A photograph made by Suarez from a lower elevation clearly shows the scattering and absorption of sunlight by the thick dust.
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Amateur meteorologist Sergio Suarez photographed the bright aureole around the Sun caused by scattering of sunlight by a thick layer of Sahara dust as it crossed over Tenerife, Canary Islands, on or about 3 March 2004. See Foro Canariasmet at http://meteo.viajesinsular.es. Click image to enlarge. |
The E-Bulletin thanks Amateur meteorologists Eugenio Rodriguez and Sergio Suarez for the use of their photographs, which provide an outstanding example of how citizen scientists can document major atmospheric aerosol events that are also imaged by various satellites.
Foro
Canariasmet is a web site featuring a discussion forum that discusses
Sahara dust events. The site is at http://meteo.viajesinsular.es.
