Man-made fires can worsen drought in Africa

Smoke pollution from human cooking fires has a major effect on amount of rainfall in the tropics, according to researchers

From Greg Lefevre
CNN San Francisco Bureau Chief

SAN FRANCISCO, California (CNN) -- Fires made by humans for cooking and other reasons in the African tropics slow down rainfall and can contribute to drought on the continent, according to a new report.

Scientists studying the world's tropical rainfall determined that a storm over a populated area in Africa may generate only half the rain as the same kind of storm over the ocean.

A main reason is smoke pollution, according to lead scientist Daniel Rosenfeld, a professor of meteorology at the Hebrew University of Jerusalem.

"The smoke and pollution particles, when going into the clouds, distribute the water into many small droplets. They are so small that they are very slow into combining into raindrops and other icy precipitation particles," Rosenfeld said.

VIDEO CNN's Greg Lefevre reports that a recently concluded, three-year study found that air pollution causes a decline in rainfall amounts Play video (QuickTime, Real or Windows Media) Watch NASA animated maps of rainfall for 1998-2000 Play video (QuickTime, Real or Windows Media)     MESSAGE BOARD Environmental issues     ALSO Vicious cycle: Global warming feeds fire potential November 2, 2000 Get smart: satellite refines rainfall forecasts January 19, 2000     INTERACTIVE Images and animation from the TRMM satellite

Clouds formed in dirty air "produce as little as half of the rainfall from clouds of the same size in clean air," he said. Other factors contribute to the drought as well. For example, desert dust in the clouds makes them less efficient rain producers, according to the three-year study.

"The major global environmental problem of the 21st century is water, the amount of the water and the quality," Rosenfeld said. "It is really a matter of famine or no famine,"

The report observations come from data obtained from a satellite in low-Earth orbit, launched jointly by Japan and the United States in 1997. Called Tropical Rainfall Measuring Mission (TRMM), the orbiter scans and maps tropical storms with radar and microwave instruments from an altitude of 217 miles (350 km).

Seventy-five percent of world rainfall takes place in tropical zones in middle latitudes around the equator.

The TRMM satellite, which has exceeded its three-year life expectancy, has improved storm forecasting considerably. By measuring the actual amount of rainfall in storms, scientists can now better predict the damage such storms might cause.

Information from the satellite "can make a significant improvement in forecasts," said Bob Adler of the NASA Goddard Space Flight Center, citing better rainfall predictions and hurricane tracking.

Rosenfeld presented his study this week a meeting of the American Geophysical Union in San Francisco.

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Institute Earth Sciences
University of Utah - Department of Meteorology
NASA Goddard Space Flight Center
American Geophysical Union

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