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Researcher wins presidential award for work on rain forests and rainfall

An MIT scientist whose work provided evidence that deforestation of specific sections of rain forest increases the prospect of widespread regional drought was recently selected by President Clinton to receive a Presidential Early Career Award for Science and Engineering.

Dr. Elfatih Eltahir, the Gilbert Winslow Career Development Assistant Professor of Civil and Environmental Engineering, was nominated by NASA for the honor based on his work in hydroclimatology. The award cites Professor Eltahir's "outstanding accomplishment in hydrology and hydroclimatology by combining theory and remote sensing observations to better understand the links between the biosphere and the atmosphere and their implications for regional water resources in the tropics."

"These gifted young professionals exemplify the best of our science and technology community and will help set the scientific pace for the United States and the world in the years ahead," said President Clinton in announcing the 60 recipients. The award includes up to $500,000 over a five-year period and is "the highest honor bestowed by the US government on outstanding scientists and engineers at the outset of their independent research careers."

Professor Eltahir studies how vegetative cover and soil moisture content affect land-atmosphere-ocean interactions at the regional level. Some of his recent work suggested that deforestation along the southern coast of West Africa could cause a collapse of the monsoon system and lead to notable decrease in rainfall for the entire Sahel region.

"West Africa is a region that has seen both significant deforestation activity and a decline in rainfall. We're asking if the 30-year drought is part of the natural variation in the system or is caused by human activity," said Professor Eltahir.

He and postdoctoral assistant Xinyu Zheng published a paper in Geophysical Research Letters earlier this year that described their model of the West African monsoon and its response to deforestation and desertification. Other researchers have suggested that deforestation has an effect on climate, but this was the first published study to suggest that the potential impact of the deforestation depends on the precise location of the loss of vegetative cover.

"Desertification along the border with the Sahara leaves a relatively minor impact on monsoon circulation and regional rainfall; deforestation along the southern coast of West Africa may result in complete collapse of monsoon circulation, and a significant reduction of regional rainfall," said the authors.

To create their model, Professor Eltahir and Dr. Zheng used data obtained by NASA satellites and other sources. Among the variables used by the model are surface temperature, rainfall, wind and humidity, as well as atmospheric temperature and water vapor.

The research team is also modeling the hydrological cycle of the American Midwest by studying atmospheric variables, soil moisture and ground water levels in Illinois. Professor Eltahir hopes that a clearer understanding of that cycle will help to determine if an increase in greenhouse gases will cause drier summers in that major agricultural region.

"Understanding these process in the current climate should eventually help us to project the impact of future climate change on water resources in the region," said Professor Eltahir, who plans to present this work in December at a meeting of the American Geophysical Union.

His assessment of the consequences of human activity on regional climate will likely contribute to a broader understanding of global climate change and its impact on water resources. "If we can understand how the natural system works with regard to soil moisture and rainfall, it will help us later to identify how any global change scenario may impact the regional hydrology and water resources. Such impacts represent a serious threat to the sustainability of water resources," he said.

A version of this article appeared in MIT Tech Talk on November 19, 1997.

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