Acta Geographica Sinica ›› 2007, Vol. 62 ›› Issue (11): 1142-1152.doi: 10.11821/xb200711003

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The Temporal and Spatial Distribution of Seasonal Dry- Wet Changes over the Northwestern China: Based on PDSI

ZHANG Yong1, CHEN Fahu1, GOU Xiaohua1, JIN Linya1, TIAN Qinhua1,2, WANG Yousheng3, PENG Jianfeng1   

  1. 1. CAEP, National Laboratory of Western China's Environmental System, Lanzhou University, Lanzhou 730000, China;
    2. Institute of Earth Environment, CAS, Xi'an 710075, China;
    3. Gansu Meteorological Bureau, Lanzhou 730000, China
  • Received:2007-05-15 Revised:2007-07-05 Online:2007-11-25 Published:2007-11-25
  • Supported by:

    National Natural Science Foundation of China, No.40671191; No.90502008; Innovation Team Project of NSFC, No.40421101; Program for New Century Excellent Talents in Universities, Ministry of Education, No.NCET-05-0888; Chinese 111 Project, No.B06026


Using global Palmer drought severity index (PDSI) database, the seasonal and annual PDSI mean values of 56 grid points covering the period 1953-2003 over northwestern China is analyzed by rotated experience orthogonal function (REOF). The results show that the seasonal and annual means display similar anomaly regions, and furthermore there are five main anomaly regions in the northwestern China based on the annual PDSI mean, i.e., the northern and southern parts of Xinjiang, northern part of plateau, western part of Inner Mongolia and eastern part of northwestern China. The opposite changes of dry-wet conditions are discovered after comparing the curves of feature point series and binomial fit between the eastern and western parts of the northwestern China: The western part of the northwestern China influenced by westerly, a trend of wetting gradually occurred since 1980. On the contrary, a trend of drying gradually occurred in the eastern part of the northwestern China which is mainly influenced by Asian monsoon, and especially in summer and autumn, there is notable trend of drying over the southeastern part of the northwestern China. The northwestern China is obviously affected by westerly, Asian monsoon and Tibetan Plateau. There are differences among the responses of the dry-wet conditions to the global warming in different regions.

Key words: northwestern China, REOF, PDSI, westerly, monsoon, dry-wet condition