New York June 5, 2011 Moisture and heat fluctuations from the land surface to the atmosphere form a critical nexus between surface hydrology and atmospheric processes, especially those relevant to rainfall. While current theory has suggested that soil moisture has had a positive impact on precipitation, there have been very few large-scale observations of this. A team of researchers from Columbia Engineering, Geophysical Fluid Dynamics Laboratory, and Rutgers University has now demonstrated that evaporation from the land surface is able to modify summertime rainfall east of the Mississippi and in the monsoonal region in the southern U.S. and Mexico. One of their main findings is that evaporation from the land is, however, only able to modify the frequency of summertime rainfall, not its quantity.
"This is a major shift in our understanding of the coupling between the land surface and the atmosphere, and fundamental for our understanding of the prolongation of hydrological extremes like floods and droughts," said Pierre Gentine, Assistant Professor of Applied Mathematics at The Fu Foundation School for Engineering and Applied Science at Columbia University, and co-author of the paper "Probability of Afternoon Precipitation in eastern United States and Mexico Enhanced by High Evaporation," published in the June 5th online edition of Nature Geoscience. The other co-authors are Kirsten Findell (Geophysical Fluid Dynamics Laboratory), Benjamin Lintner (Rutgers University), and Christopher Kerr (Geophysical Fluid Dynamics Laboratory).
The researchers used data from the National Centers for Environmental Prediction (NCEP) to quantify the impacts of continental evaporation on the frequency and intensity of summertime rainfall over North America. They discovered that higher evaporation increases the probability of afternoon rainfall east of the Mississippi and in Mexico, while it has no influence on rainfall over the Western U.S. The differ
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