THE FLUCTUATION OF DRY AND WET CLIMATE BOUNDARY AND ITS CAUSAL ANALYSES IN CHINA
Yang Jianping Ding Yongjian Chen Rensheng (Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000) Liu Lianyou (Resources and Environment Institute, Beijing Normal University, Beijing 100875)
Based on the yearly precipitation, annual mean wind, solar radiation data during 1951-1999 of 295 stations, the aridity index is calculated in this paper. According to aridity index( D ), the climatic regions in China are delineated into three types, namely, arid region, semi-arid region and humid region. D =0.20 is the boundary between arid and semi-arid region. D =0.50 is the boundary between semi-arid and humid climate region. Dry and wet climate in China fluctuate markedly and differentiate greatly in each region over past 50 years. Semi-arid region is the transitional region between humid and arid regions, the border belt of monsoon in China and the susceptible region of environmental evolution. During 1960's and 1970's dry and wet climate in China had abrupt changes, which turned wetness into drought. Moreover, drought has an increasing trend. Dry and wet climate boundaries show the fluctuation characteristics of the whole shifts and the opposite fluctuations in east, west, south and north directions. The fluctuation of climatic boundary and the dry and wet variation of climate have substantial inter-decadal features. The main factors affecting the fluctuations of dry and wet climate boundary and the dry and wet variations of climate in China are southeast monsoon, southwest monsoon, plateau monsoon in the Tibetan Plateau, westerly circulation, and West Pacific subtropical high. The different circulation and the strong and weak combination of different circulation result in the regional difference of dry and wet climate change in China. Inter-decadal changes of the fluctuation of dry and wet climate boundaries and of arid and humid change of climate result from the inter-decadal variations of southeast monsoon, southwest monsoon, plateau monsoon in the Tibetan Plateau, westerly circulation, and West Pacific subtropical high. The anomalous atmospheric circulation of Northern Hemisphere in 1960's and 1970's was the causes for the abrupt change of arid and humid climate.
【Fund】： 中国科学院知识创新重大项目 (KZCX1-10 -0 6);; 沙漠化973项目 (2 0 0 0 0 4870 5 )
【CateGory Index】： P468
【CateGory Index】： P468