长江流域大范围旱涝与南亚高压的关系

THE LARGE AREA FLOOD AND DROUGHT OVER YANGTZE RIVER VALLEY AND ITS RELATION TO THE SOUTH ASIA HIGH

中文关键词:  旱涝  南亚高压  西太平洋副热带高压  海面温度异常距平

英文关键词:Flood and drought  South Asia high  Western Pacific subtropical high  SSTA

中文摘要:

      利用1958～1999年月平均气象资料,分析了42a以来长江流域大范围旱涝的时空分布特征,发现长江流域降水具有非常明显的年代际变化,年代际的转折发生于20世纪70年代末,60年代的持续干旱和90年代的多发性洪涝形成鲜明对比。依照降水标准差大小,从42a降水资料中划分出6个严重涝年和5个严重旱年。合成分析表明旱涝年大气环流和全球海温均有明显差异,涝年高低层副热带高压偏南偏强,全球海温呈大范围正距平,旱年则相反。文中对比分析了南亚高压和海温两个异常因子与夏季长江流域降水的关系,发现南亚高压强度指数与长江流域降水有显著相关,二者的年代际变化趋势非常一致,20世纪70年代末当南亚高压由弱变强,长江流域由相对干旱转为相对多雨。而赤道太平洋SSTA与长江流域降水的关系不甚确定。超前/滞后相关分析表明,前期冬春季100hPa副热带高压强度与夏季长江流域降水呈显著的正相关,前期冬春季赤道东太平洋SSTA与长江流域降水也呈正相关,但相关不显著。分析结果表明,由于中国特殊的地理环境、地形和海陆分布特征,将南亚高压作为一个异常强信号并加以关注,对中国短期气候尤其是灾害性气候的预测具有重要意义。

英文摘要:

      The temporal and spatial distributions of the summertime precipitation over Yangtze River Valley are examined in this paper by employing monthly mean observation data from 1958 to 1999. There is a distinct interdecadal trend in precipitation and the transition occurs in late 1970s. The significant contrast can he found in the persistent drought during 1960s and frequent occurrence of flood during 1990s. According to the standard deviation of the precipitation, the 6 severe flood years 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 subtropical 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 simultaneous correlation shows the significant positive correlation between SAH intensity index and precipitation anomalies in the Yangtze River Valley.When the SAH changes from a relative 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 the relationship between the Yangtze River Valley precipitation and Equatorial Eastern Pacific SSTA is uncertain. The lead/llag correlation also shows the significant positive correlation between the intensity of winter/spring 100 hPa subtropical high and summertime Yangtze River Valley precipitation.The results of the paper suggest that due to the special geographic and land-sea distribution of China, the anomaly of the SAH has more direct impact on regional climate of China than that of ENSO. Thus we propose that the SAH should be considered as a strong anomalows signal and be paid more attention to.