Three indices are defined to represent the characteristics of rain-band patterns in summer in eastern China and the differences of ocean and atmospheric circulation features among the three rainfall-band patterns are analyzed in terms of the East Asian circulation, moisture transport and sea surface temperature (SST) by using the NCEP/NCAR reanalysis data, the UK-MO HADISST1 global monthly SST data and the monthly precipitation data of 120 stations in eastern China during 1950— 2009. The results show that : (1) The differences of the ocean climatic background among the three rainfall-band patterns are as fellows: pattern 1 in which the rainy belt is located in the northern part of China corresponds to a pattern of positive SST a-nomalies in the North Pacific, negative SST anomalies in the warm pool and the warm currents over eastern Australian and positive SST anomalies in the westerly drift region over the South Pacific; pattern II in which the rainy belt is located between the Huanghe River and Huaihe River regions corresponds a pattern opposite to pattern I and pattern III in which the rainy belt is located in the area south of the Yangtze River corresponds to a pattern of the SST anomaly distribution in the North Pacific consistent with that in pattern I . (2) The differences of characteristics of circulations and water vapor transports among the three rainfall-band patterns are as fellows: the characteristics of pattern III are almost opposite to pattern I ; when pattern m appeared in the eastern China, the strongest blocking appeared in the middle and high latitudes of East Asia, the latitudinal circulation anomaly was stronger and the subtropical high over the western North Pacific was obviously stronger with its position more southward and westward than normal; meanwhile, anticyclonic anomalies circulations appeared in the western North Pacific and the latitudinal water vapor transport was strengthened in the area. The above characteristics are opposite when pattern I appeared. The characteristics of pattern H are close to pattern I and the differences between these two appeared in the subtropical area over the western North Pacific. When pattern II occurred the anticyclonic anomalies circulation appeared in the area while when pattern I occurred the cyclonic one appeared in the area. (3) SST anomalies in the equatorial central and eastern Pacific and the westerly drift region of the South Pacific in winter are premonitory signals for forecasting the subtropical high caver the western North Pacific in summer.%利用1951-2009年NCEP/NCAR再分析资料、UKMO HADISST1全球月海表温度及中国东部地区120站的月降水量资料,首先定义出能够客观表征中国东部夏季3种雨带类型的指数,然后分析了3种雨带分布类型海洋和大气环流特征的主要差异,并进一步分析了前期海洋背景的差异特征对夏季东亚环流关键系统的预测蕴示.结果表明:(1)3种雨带类型对应的前期冬季海洋信号比当年夏季强,其差异主要表现在:多雨带出现在北方地区的Ⅰ型对应的是北太平洋海温呈显著的正距平、暖池及东澳暖流为负距平、南太平洋西风漂流区为正距平;多雨带出现在黄淮地区的Ⅱ型对应的海温分布则与Ⅰ型完全相反;多雨带出现在长江及其以南地区的Ⅲ型对应的海温分布在北太平洋海域与Ⅰ型基本一致;(2)3种雨带类型对应的环流及水汽输送特征的差异主要表现在:Ⅲ型与Ⅰ型具有几乎完全相反的环流及水汽输送特征,当出现Ⅲ型时,东亚中高纬度有强盛的阻塞形势发展和维持,中高纬度的经向环流异常加强,同时西太平洋副热带高压偏强,位置偏西、偏南,该地区呈反气旋性距平环流,西太平洋副热带纬向水汽输送加强,而出现Ⅰ型时则相反;Ⅱ型与Ⅰ型的环流及水汽输送特征更接近,两者的主要差异是:当出现Ⅱ型时,西太平洋副热带地区呈反气旋性距平环流,而出现Ⅰ型时该地区呈气旋性距平环流;(3)前期冬季赤道中东太平洋海温和南太平洋西风漂流区的海温异常变化可以作为夏季西太平洋副热带高压预报的重要前兆信号.
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