中国东部夏季风雨带季内变化各模态的环流及海温特征

Characteristics of the Atmospheric Circulation and Sea Surface Temperature for Different Modes of Intraseasonal Variation of Summer Monsoon Rain Belt in Eastern China

本文根据中国气象局国家气候中心提供的中国160站月平均降水量,NCEP/NCAR再分析的850 hPa风场,及NOAA扩展重建的海温场资料,用合成分析和相关分析,研究了1951～2005年间中国夏季风雨带季内变化各模态的西太平洋副高夏季各月活动特点的差异,及其与前期冬季东亚季风和太平洋海温异常的联系,并分析了我国夏季风雨带季内变化各模态与夏季雨型的关系。结果表明,不仅不同模态对应的西太平洋副高自春至夏的两次北跳有明显不同的过程,而且两次北跳还具有相对独立性。第一次北跳主要对6月的雨带特征有重要影响,第二次北跳对7、8两月的雨带分布有决定性意义。太平洋海温异常对我国夏季风雨带季内变化的影响是多态的,在不同季风—ENSO循环的位相有不同的表现。第一模态主要出现在El Nio减弱位相,第二模态在La Nia发展位相,第三模态在El Nio发展位相,第四模态在La Nia减弱位相,第五模态ENSO的信号较弱,第六模态在La Nia持续位相。此外,不同海洋关键区的海温异常对我国雨带季内变化也有不同的调控作用。黑潮区的海温与6月的雨带活动关系密切,而赤道东太平洋的ENSO循环对7、8两月的雨带有重要影响。对我国夏季风雨带季内变化模态与夏季雨型关系的分析则表明,它们之间存在某些联系,但这并不意味着可以相互取代。

Differences in monthly evolution of the western Pacific subtropical high （WPSH） in summer for different modes of intraseasonal variation of the summer monsoon rain belt （IVSMRB） are examined by using the composition method. For such analysis, the rainfall data from 160 stations in China, 850 hPa wind derived from the National Centers for Environmental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） reanalysis dataset, and the National Oceanic and Atmospheric Administration （NOAA） extended reconstructed sea surface temperature （SST）, are used. In addition, the characteristics of the pre-winter East Asia monsoon, Pacific sea surface temperature anomalies （SSTA）, and rain styles in summer relative to these modes are investigated by using composition and correlation methods.Results show that the twice northward jumps of WPSH from spring to summer differ significantly among the modes, and that for each mode is relatively independent. The first jump of WPSH has an important influence on rain belt distribution in June, while the second jump has decisive influence on that in July and August. The influence of SSTA in the Pacific on IVSMRB in China is multi-modal. In different phases of the Monsoon/E1 Nifio-Southern Oscillation （ENSO） cycle, the IVSMRB presents dissimilar features. The first mode appears mainly in the decay phase of E1 Nifio, and the second generally appears in the developing phase of La Nifia. The third occurs in the developing phase of El Nifio; the fourth, in the decay phase of La Nifia; the fifth, at weak ENSO signals; and the sixth, in the persisting phase of La Nifia. Moreover, the SSTA in different key regions has different impact on the IVSMRB. The SSTA in Kuroshio has a strong correlation with the rain belt variation in June, while the ENSO cycle in eastem tropical Pacific has an important influence on the rain belt variation in July and August. Analysis of the relationship between the IVSMRB modes and summer rain styles reveals some linkage between the two; however, these results do not imply that they can be substituted for each other.