Guangyao Gao, State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China, Jianjun Zhang, School of Land Science and Technology, China University of Geosciences, Beijing, China, Bojie Fu, Chinese Academy of Sciences, Beijng, China and Hoshin Vijai Gupta, University of Arizona, Department of Hydrology and Atmospheric Sciences, Tucson, AZ, United States