1. a Department of Environmental Sciences , University of Virginia , Charlottesville, VA, 22903, USA
2. b Joint Research Centre , Ispra, 21020, Italy
3. c Geography Department , University of Maryland , c/o NASA-GSFC, Code 923, Greenbelt, Maryland, 20770, USA
4. d Department of Geography , University of London , 26 Bedford Way, London, WC1H 0AP, UK
5. e NASA-GSFC , Code 923, Greenbelt, Maryland, 20770, USA
6. f INRA Bioclimatology , Avignon, 84 914, France