1. a Hydrological Sciences Branch , NASA/Goddard Space Flight Centre , Greenbelt, Maryland, 20771, U.S.A.
2. b Science , Systems and Applications , 7375 Executive Place, Seabrook, Maryland, 20706, U.S.A.
3. c Department of Meteorology , Florida State University , Tallahassee, Florida, 32306, U.S.A.
4. d Ecole Nationale Superieure de Physique de Strasbourg , Universite Louis Pasteur , 7 rue de I'Universite, Strasbourg, F-67000, France