1. Department of Geographical Sciences, University of Maryland, College Park, MD 20740, USA.
2. State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China.
3. Department of Geosciences, Texas Tech University, Lubbock, TX 79409, USA.
4. State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USA.