1. The Institute of Geography and Resources Science; Sichuan Normal University; Chengdu 610068 China
2. Xinjiang Institute of Ecology and Geography; Chinese Academy of Sciences; Urumqi 830011 China
3. Tianshan Station for Snow & Avalanche Research; Urumqi 830011 China
4. Institute of Desert Meteorology; China Meteorological Administration; Urumqi 830002 China