Fahu Chen^1,2, Huan Xia³, Guanghui Dong³ and Dongju Zhang³, (1)ITP Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China, (2)Lanzhou University, MOE Key Laboratory of West China's Environmental System, College of Earth and Environmental Sciences, Lanzhou, China, (3)Lanzhou University, MOE Key Laboratory of Western China's Environmental Systems, College of Earth Environmental Sciences, Lanzhou, China