索马里急流多时间尺度的变化特征及其与中国降水的联系

MULTI-TIME SCALE VARIATION CHARACTERISTICS OF SOMALI JET AND ITS CONTACT WITH PRECIPITATION IN CHINA

利用欧洲中心的再分析风场资料,采用相关分析、合成分析等方法,分析索马里急流活动的多时间尺度变化特征,研究其在年际、年代际尺度和季节以内尺度对中国降水的影响。结果表明,索马里急流强度的年代际变化特征较明显,急流在1960年代逐渐变弱,1970年代初最弱,1970年代末期开始缓慢增强。索马里急流在不同时间尺度上与中国夏季降水都有较密切的联系,初步分析表明,在年际尺度上索马里急流建立初期的5、6月与后期降水的超前相关性较好,在年代际尺度上急流与同尺度中国降水的关系密切。无论是超前还是同期相关,索马里急流强度与中国典型相关区降水的关系存在明显的年代际变化特征。此外,季节以内尺度索马里急流强度异常与过程也存在一定联系,在夏半年急流的主要活动时期,索马里急流强度的正(负)异常对应中国的降水偏多(少),且正距平异常时对中国降水的影响更大。

Based on the ERA reanalysis wind data, the multi-time scale activity of Somali Jet is analyzed synthetically and its influences on rainfall in China, including the jet＇s variations on interannual and interdecadal scales as well as the sub-monthly scale, are also studied using correlation analysis and the composite method. The results demonstrate that there are significant interdecadal variations. The Somali jet became weaker in the 1960s and was the weakest in the early 1970s before increasing slowly in the late 1970s. Moreover, correlations are close between the Somali jet and summer precipitation in China but vary on different time scales. Preliminary analysis shows that the strength variations in May and June during the early days of establishment are well correlated with summer precipitation. The Somali jet intensity on the interdecadal scale is closely related with interdecadal variations of the precipitation in China. Regardless of preceding or simultaneous correlation, the relationship between the Somali jet strength and the rainfall in China＇s canonical correlation areas show obvious interdecadal variations. Moreover, the link between the intensity anomaly of the jet in the summer-half of the year on the synoptic scale and precipitation processes in China is further discussed. China has more rainfall with positive anomalies but less rainfall with negative anomalies in the main jet activities period in the summer-half of the year, and the positive events influence more on the precipitation in China.