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《Acta Meteorologica Sinica》 2001-05
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THE LARGE AREA FLOOD AND DROUGHT OVER YANGTZE RIVER VALLEY AND ITS RELATION TO THE SOUTH ASIA HIGH

Zhang Qiong, Wu Guoxiong (Institute of Atmospheric Physics,Chinese Academy of Sciences, State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics,Beijing 100029)  
The temporal and spatial distributions of the summertime precipitation over Yang tze River Valley are examined in this paper by employing monthly mean observatio n data from 1958 to 1999.There is a distinct interdecadal trend in precipitation and the transition occurs in late 1970s.The significant contrast can be found i n the persistent drought during 1960s and frequent occurrence of flood during 1990s.According to the standard deviation of the precipitation,the 6 severe flood yea rs and 5 severe drought years are identified during the past 42 years.The obvious differences between flood year and drought year are found in the troposphere and stratosphere circulations as well as in the global SSTA .The subtropica l high at both upper and lower troposphere shifts southward and becomes strengthened during the flood year,meanwhile the global SST exhibits large area positive anomalies ,and vice versa during the drought year.The sim ultaneous cor relation shows the significant positive correlation between SAH intensity index and precipitation anomalies in the Yangtze River Valley .When the SAH changes fr om a relat ive weak period to a strong period at the end of 1970s,the Yangtze River valley precipitation changs from a relative drought period to a flood period;whereas th e r elationship between the Yangtze River Valley precipitation and Equatorial Easter n Pacific SSTA is uncertain.The lead/lag correlation also shows the significant p ositive correlation between the intensity of winter/spring 100 hPa subtropical h igh and summertime Yangtze River Valley precipitation. The results of the paper suggest that due to the special geographic and land s ea distribution of China,the anomaly of the SAH has more direct impact on region al climate of China than that of ENSO.Thus we propose that the SAH should be con sidered as a strong anomalous signal and be paid more attention to.
【Fund】: 国家重点基础研究发展规划项目“我国重大气候灾害形成机理和预测理论的研究”;; 国家自然科学基金项目(40005006,400230
【CateGory Index】: P426.616
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