【摘要】 利用1961~2000年NCEP/NCAR再分析资料、扩展重建的海表温度资料(ERSST)和中国730个站旬降水资料,采用SVD和扩展SVD(ESVD)分析、合成分析、相关分析等方法,在分析中国梅雨期降水与同期大气环流和前期冬季海温之间关系的基础上,研究了ENSO盛期海温异常导致与长江流域梅雨期降水密切相关的东亚/太平洋(EAP)遥相关型形成的过程,及与ENSO相关的海温和大气环流异常的持续性问题。结果表明,梅雨期EAP遥相关型的出现与ENSO遥强迫作用有密切关系。联系冬季ENSO和梅雨期EAP遥相关型的关键过程主要有三个:(1)西北太平洋低纬地区异常反气旋环流的形成和维持,它在冬季形成后一直可维持到夏季,使得夏季西北太平洋副热带高压偏南偏强;(2)东亚大槽持续偏弱,冷空气活动路径偏北偏东,使西北太平洋海温呈亲潮区偏冷、黑潮区偏暖的海温分布;(3)PNA遥相关型的持续发展,使北冰洋地区高度增高。后二者通过局地海气相互作用和大气内部调整过程对初夏鄂霍次克海阻塞形势的形成起重要作用。另外,持续性分析表明,ENSO年大气环流和海温距平型的持续性要比非ENSO年大得多。在ENSO年大气环流和海温之间存在很强的相互作用耦合关系,ENSO引起的大气环流异常可导致太平洋海温异常,而海温异常一旦形成反过来又可导致大气环流异常的稳定和维持,对后期初夏东亚季风和我国天气气候产生明显滞后效应。更多还原

【Abstract】 By using NCEP/NCAR reanalysis datasets,extended reconstructed sea surface temperature(ERSST) data and Chinese 730-station ten days mean rainfall for the period of 1961-2000,the relationship between the rainfall of China and circulation during the Meiyu period and pre-winter sea surface temperature(SST) is studied through singular value decomposition(SVD),extended singular value decomposition(ESVD),composition and correlation methods.On this basis,the evolution of ENSO-related SST and circulation anomalies over East Asia and the Pacific and their persistence,particular attention being paid to the formation of the East Asia-Pacific(EAP) teleconnection pattern related to the Meiyu rainfall in the Yangtze River valley,is investigated.The results show that the appearance of EAP teleconnection pattern in the Meiyu period is closely linked to the remote ENSO forcing.The formation of the EAP teleconnection pattern linked to ENSO in the mature Phase consists of three key processes:(1) The formation and persistence of anomalous anticyclone in the western North Pacific: The anticyclone persists from the mature El Nio winter to the ensuing summer,leading to the western North Pacific subtropical high strengthening and southward shifting;(2) the decay of the East Asia trough: The weak East Asia trough causes the path of cold air activity more northward and eastward and the SST cooling in Oyashio and warming in Kuroshio;(3) the continuous development of the PNA(Pacific-North American) teleconnection pattern: The blocking high over the region of Alaska extends westward,making the geopotential height increase over the Arctic Ocean.The above processes of the East Asia trough and PNA teleconnection pattern will play important roles in the establishment of the blocking high over the Sea of Okhotsk in early summer through local air-sea interaction and adjustment of atmosphere circulation. Furthermore,the analysis shows that the persistence of the anomalous circulation and SST patterns is much longer in ENSO years after the mature phase than non-ENSO years.There is strong coupled relation between the circulation and SST in ENSO years.The ENSO-related circulation anomaly could lead to the Pacific SST anomaly which in turn could result in a bigger stability of anomalous circulation pattern.So it has obvious delayed effect on East Asia monsoon and China’s weather and climate process in early summer after El Nio mature phase.更多还原