1. a International Institute for Geo‐information Sciences and Earth Observation , Department of Water Resources , Box 6, 7500 AA, Enschede, The Netherlands
2. b Duke University , Department of Civil and Environmental Engineering , Box 90287, Durham, NC 27708
3. c INRA Climat , Sol et Environnement , Batiment Climat , F‐84914 Avignon Cedex 9, France