National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [41571344, 41331174, 41071261, 40906092, 40971193, 41101415, 41401388, 41206169, 41406205]; Open Research Fund of the Key Laboratory of Space Ocean Remote Sensing and Application; State Oceanic Administration People's Republic of China [201502003]; Hong Kong Research Grants Council (RGC) General Research Fund [B-Q23G]; Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin; China Institute of Water Resources and Hydropower Research [IWHR-SKL-201514]; Major Science and Technology Program for Water Pollution Control and Treatment [2013ZX07105-005]; Open Research Fund of Key Laboratory of Digital Earth Science; Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences [2013LDE004]; Special Fund by Surveying & Mapping and Geoinformation Research in the Public Interest [201512026]; LIESMARS Special Research Funding; '985 Project' of Wuhan University; Special funds of State Key Laboratory