1. a Hydrological Sciences Branch/974, Laboratory for Hydrospheric Processes, NASA/Goddard Space Flight Center , Greenbelt, MD, 20771, U.S.A
2. b Department of Electrical Engineering and Computer Science , George Washington University , Washington, DC, 20052, U.S.A
3. c USDA/ARS Hydrology Laboratory , Room 104, Bldg. 007, BARC-WEST, Beltsville, MD, 20705, U.S.A