1. The Key Laboratory of Tree-ring Physical and Chemical Research of China Meteorological Administration; Institute of Desert Meteorology; China Meteorological Administration; Urumqi 830002 China
2. Xinjiang Laboratory of Tree-ring Ecology; Institute of Desert Meteorology; China Meteorological Administration; Urumqi 830002 China
3. College of Earth and Environmental Science; Lanzhou University; Lanzhou 73000 China
4. Department of Geography; Swansea University; Singleton Park Swansea SA2 8PP UK