Rain machines

Science News, Feb 14, 2009 by Sid Perkins

Tropical cyclones, including hurricanes and their weaker cousins, typically last only a short time and cover a relatively small area. But at some latitudes these storms provide a substantial part of a region's rainfall, a new study suggests. Using satellite data, Christopher L. Williams, a recent graduate of Georgia Tech in Atlanta, and Frank Marks Jr.

of NOAA's Hurricane Research Division in Miami estimated rain amounts dumped by the cyclones and total worldwide rainfall for 1998-2007. Overall, tropical cyclones drop about 2 to 3 percent of the world's rainfall. But at latitudes between 15[degrees] and 30[degrees], rain is less abundant, and tropical cyclones account for as much as 17 percent of annual rainfall.