【摘要】 利用历史数据,研究了西太平洋副热带高压指数的特征,证实脊线指数和西伸脊点指数可以较好地描述西太平洋副热带高压,同时也指出这两个指数的年际和年代际变化及其不同的配置,是造成中国夏季降水时空分布和旱涝异常的复杂性、多变性的主要原因之一。据此,将西太平洋副热带高压西伸脊点指数和脊线指数的距平投影到二维平面上,对西太平洋副热带高压进行了分类,并对其各种类型下中国夏季降水进行了合成分析,发现夏季西太平洋副热带高压西伸脊点和脊线不同配置下中国夏季降水的总体分布具有明显的规律性:在西太平洋副热带高压脊线偏北的情况下,夏季降水总体表现出南北两条雨带;在西太平洋副热带高压脊线正常的情况下,夏季降水总体表现为北多南少,长江以北降水偏多;在西太平洋副热带高压脊线偏南的情况下,夏季降水总体表现为南多北少,长江流域及其以南地区降水偏多;上述3种情况下西伸脊点越偏西,降水范围越大。此外,通过计算1951—2010年各年夏季降水实况与其西太平洋副热带高压所属年份夏季降水合成的距平相关系数,发现同一类型下各年夏季降水与其合成分布总体相似,说明了西太平洋副热带高压位置对中国降水具有明显的影响,同时也说明此种分类具有一定的合理性。最后,通过对9种西太平洋副热带高压类型下北半球夏季500hPa高度场和850hPa风场距平分别进行合成,对不同西太平洋副热带高压类型下中国夏季降水的大尺度环流背景和可能机理进行了分析。更多还原

【Abstract】 The characteristics of the western Pacific subtropical high indices were studied based on the historical data. It was proved that its ridge line index and western extension index could be used to describe the subtropical high well, and the interannual and interdecadal variations of this two indices and their different configurations in space contributed largely to the complexity and variability of the spatial-temporal rainfall distribution and precipitation anomalies in summer of China. Accordingly, anomalies of the summer average ridge index and western extension index of the subtropical high were projected onto a two-dimensional plane, and the subtropical high was classified and the seasonal rainfall was analyzed by the synthesis method based on the different categories. The results indicate that the overall distribution patterns show distinct regulations under the different configurations of the two indices. There are two rain-belts in the summer precipitation respectively in southern and northern China when the subtropical high ridge shifts northward. The normal pattern for the subtropical high ridge is corresponding with that with the precipitation more in the north of the Yangtze River regions and less in southern China. While the distribution of precipitation is opposite when the subtropical high ridge shifts southward. Under the circumstances mentioned, the more the westward extention of the subtropical high is, the larger the precipitation range is. Furthermore, the correlation coefficients between summer precipitation anomalies and the synthesized precipitation based on the classification of the corresponding subtropical high were calculated, and found that the anomaly patterns of summer precipitation anomaly is similar to that of the synthetic one of the same category, which indicated some rationality of the classification to some extent. Finally, the composite analysis was done for the 500 hPa geopotential height field and the 850 hPa wind anomaly field by the nine types of the subtropical high in summer, and the probable mechanisms and background of the large scale circulation were analyzed.更多还原