华北夏季降水地域特征的旋转主分量研究及其相关分析

用旋转主分量(RPC)方法,研究华北降水的空间分布特征.给出了华北降水空间分布的RPC的前10个模态.它们概括了华北地区降水的基本特征及历史上的大旱和大涝年的地域分布.每一种降水模态的时间系数都表现出了长周期的年代际变化的规律.华北发生大旱与大涝的最可能的分布是模态3、4与模态10.如1965、1968和1983年的大旱;1963和1973年的大涝年等.分析了各个模态与太平洋副热带高压强度、东亚环流指数、前冬赤道东太平洋海温、以及江淮流域降水的相关表明:它们之间的相关都有各自的最佳模态.如对赤道东太平洋海温与太平洋副热带高压强度而言,最佳模态的特征是:当海温呈El Nino型和西太副高偏强时,华北降水的最可能分布是东部沿海为强的干旱区,其余地区降水皆偏多.与江淮流域降水和EAP流型的相关则主要以1954、1980及1991年为代表的第1和第9模态为主要形态.它们与华北降水有极好的反相关.

The Rotated Principal Component Analysis on the Regional Features of Summer Precipitation in North China and Their Correlation Analysis

Using the rotated principal component (RPC) analysis method, the distribution features of summer precipitation in North China is studied. Ten leading modes are given which involve the main severe cases of flooding and drought in the history. The most possible distributions for the major flooding (drought) in North China is mainly featured by modes 3. 4 and 10. as 1965, 1968 and 1983 for drought, and 1963, 1973 for flooding. Correlation analysis between the modes and the strength of the Pacific subtropical high, index of the eastern Asia circulation, SST of preceding winter at the equatorial eastern Pacific and the precipitation at the Yangtze-Huaihe River valleys shows that there exists respective optimal mode for them. With respect to the SST at the equatorial eastern Pacific and strength of the Pacific subtropical high, mode 6 bears the highest correlation. This implies that when there appear an El Nino type SST and a stronger western Pacific subtropical high, a severe drought at the eastern coastal area of North China, with more precipitation at the rest areas is likely. As for the precipitation at the Yangtze-Huaihe River valley and EAP flow pattern. Nos. 1 and 9 are the main correlated modes typical of 1954, 1980 and 1991. Normally, they are inversely correlated with the precipitation in North China.