基于台站观测和卫星观测资料及再分析数据集,本文研究了6月淮河洪涝发生时中国东部降雨型及与雨带异常相联系的环流特征、环流的季节推进异常及其机理.结果发现6月淮河流域洪涝与亚洲环流和中国东部降水联合模态的第二模态密切相关.该模态在我国东部降水表现为以长江为界北增南减的“梅雨偶极型”分布,对应的低层风场呈现出倾斜的以台湾为界,以南西太平洋是异常气旋环流,以北为反气旋环流,即西太平洋副热带高压偏北,淮河流域上存在异常西南风；同时阿拉伯海上是异常反气旋,印度上空西风偏强、降水显著偏多.这些特征是东亚和西太平洋季风区季节推进超前的反映,且与前期春季澳大利亚东北向海域海洋热含量异常偏高显著相关.该关键区海洋热含量变化是太平洋热含量变化第一模态——三极型变化的一部分,即当菲律宾以东的西太平洋和澳大利亚东北向海域海洋热含量增加,赤道中东太平洋热含量减少.该三极型海洋热含量异常从春到夏信号稳定,它激发正感热加热异常控制菲律宾以东到夏威夷以北的广大热带—副热带西太平洋地区,其北侧黑潮延伸区为负感热区.两者共同作用激发出局地反气旋在北、气旋在南,使对流层低层西太平洋副热带高压偏北.因此春季三极型海洋热含量通过影响对流层低层西太平洋副热带高压异常北移对东亚—西太平洋季节推进提前和6月淮河梅雨洪涝发生起重要作用,可作为季节预测的前期因子之一.%The rainfall pattern and circulation features associated with the Meiyu flooding of the Huaihe River valley, China in June are investigated by data analyses. The Meiyu flooding of the Huaihe River valley in June is associated with the second joint Singular Value Decomposition (SVD) mode of the Asia-Pacific circulation and rainfall. It is characterized as a 'Meiyu dipole mode' in eastern China with more rainfall to the north of the Yangtze River and less to the south. An anomaly anticyclonic circulation lies to the north of Taiwan and an anomaly cyclonic circulation lies to the south over the western Pacific in the lower troposphere. Moreover, an anticyclone is located over the Arabian Sea and the westerly winds and rainfall are strengthened over India. The above anomalies represent the lead variation in the seasonal evolution over the eastern Asia-Pacific area, and are related to the triple pattern in the oceanic heat content in the Pacific Ocean in spring. The 'triple pattern' heat anomaly stimulates the anomalies of the sea surface sensible heating and the associated subtropical anticyclone in the western Pacific. As a result, the 'Meiyu dipole mode' is induced. A heat content index can be defined and can be considered as one prediction index for Meiyu flooding events of the Huaihe River valley.
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