Ruitang Yang, Lanzhou, China, Regine Hock, Univ of AK-Geophysical Inst, Fairbanks, AK, United States, Wanqin Guo, CAREERI/CAS Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China and Kang Shichang, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China