1. NASA Goddard Space Flight Center; 8800 Greenbelt Road Greenbelt Maryland 22071 USA
2. Department of Environmental Sciences; University of Virginia; 376 Clark Hall, 291 McCormick Road Charlottesville Virginia 22904 USA
3. National Center for Atmospheric Research; 1850 Table Mesa Drive Boulder Colorado 80305 USA
4. USDA Forest Service; Rocky Mountain Research Station; 240 West Prospect Fort Collins Colorado 80526 USA