1. Department of Geography, University of California, Los Angeles, Los Angeles, California
2. Department of Geophysics, Stanford University, Stanford, California
3. Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina
4. Department of Geography, U.S. Census Bureau, Suitland, Maryland
5. Hydrologic Sciences Laboratory, Code 617, NASA Goddard Space Flight Center Greenbelt, Maryland