Coastal Cities Turn Up the Heat on Rainfall

	The image shows the Houston metropolitan area, where buildings, roads and other built surfaces create urban heat islands that can affect local rain patterns. The images were taken by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), an imaging instrument that is flying on Terra.

The old song, asking rain to "go away" and "come again another day," may get even older for people who live in large coastal cities, according to new NASA-funded research.

According to the study, urban heat islands, created from pavement and buildings in big coastal cities like Houston, cause warm air to rise and interact with sea breezes to create heavier and more frequent rainfall in and downwind of the cities. Analysis of Houston-area rain-gauge data, both prior to and since urbanization, also suggests there have been observed increases in rainfall as more heat islands were created.

The Houston-area study used data from the world's only space-based rain radar on NASA's Tropical Rainfall Measuring Mission (TRMM) satellite, and dense clusters of rain gauges.

Authors, J. Marshall Shepherd of Goddard and Steve Burian, a University of Arkansas, Fayetteville, Ark. researcher, believe the impact large coastal cities have on weather, and possibly climate, will become increasingly important as more people move into urban areas, with even greater concentrations in coastal zones. The paper is in the current American Meteorological Society and American Geophysical Union's journal, Earth Interactions.

For more on the urban rainfall study, visit: http://www.gsfc.nasa.gov/topstory/2003/0523urbanrainfall.html