1. Key Laboratory of Geographic Information Science (Ministry of Education), East China Normal University, Shanghai, China;
2. School of Geographic Sciences, East China Normal University, Shanghai, China;
3. Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, FL, USA;
4. USDA UV-B Monitoring and Research Program, Natural Resource Ecology Laboratory, and Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, USA