多种东亚冬季风指数及其与中国东部气候关系的比较

Comparisons of the multiple East Asian winter monsoon indices and their relations to climate over eastern China

利用NCEP/NCAR再分析资料及气温和降水观测资料,对比分析了12种不同定义的东亚冬季风(EAWM)指数及其与中国东部冬季温度和降水的关系。结果显示:多数EAWM指数具有较好的一致性,同时也存在差异,体现了不同定义的指数反映东亚冬季风整体性和局部性特征的侧重点有所不同。有10个EAWM指数均反映出近60年东亚冬季风呈减弱趋势,尤其是近30年最为明显,平均减弱速率达-0.25σ/10a,各指数均有强烈的年际变率和年代际波动。有10个(8个)EAWM指数与我国东部冬季温度(降水)第1模态呈显著负相关;其中西伯利亚高压指数对冬季温度年际变率方差解释率最高(53.3%),而对降水年际变率方差解释率最高的是对流层中高层东亚经向风指数(50.4%)。此外,不同EAWM指数与温度和降水的对应关系在El Nio状态、La Nia状态有不同的变化,表明在利用单个EAWM指数监测冬季气候时,要考虑到各个指数在ENSO不同状态下具有的差异性参考意义。

The East Asian winter monsoon （EAWM） is one of the most active systems in northern hemisphere during boreal winter. The EAWM exerts an essential influence on controlling winter climate over most of China, and its interannual and interdecadal variabilities are of significant importance in predicting and inspecting winter climate over China. Based on the NCEP/NCAR reanalysis data and the 160-station observational data, a comparison for 12 EAWM indices and their relations to winter temperature and precipitation o- ver eastern China have been performed in this paper. Furthermore, the stability of the relations between EAWM indices and temperature and precipitation in El Nifio status or La Nifia status has also been detected. The results indicate that most of the EAWM indices share the same variations year-to-year, but there are some differences between them at the same time, which suggest that the focuses of each index in capturing the integrity or partial features are different. It was found that the intensity of the EAWM system reduced obviously during the last 60 years, especially in the latest 30 years with a trend of - 0. 25a/10a averaging from the 10 EAWM indices. All of the 12 EAWM indices showed intense interannual variabilities and interdecadal variations during the last six decades. Al- though the exact periods of each index are not unified, the dominant interannual periods of -2 to -4a and -8 to-9a, and the dominant interdecadal periods of -13.3a and -20a of the EAWM indices can be identified from a power spectrum analysis. There are ten （eight） EAWM indices correlated significantly （0. 1%） with the first mode time series （PC1） of winter temperature （precipitation） over eastern China. Among them, the Siberian High index can explain 53.3~ variance in winter temperature PC1, and the East Asian meridional wind index derived from the middle-high troposphere can explain 50. 4% variance in winter precipitation PC1. The relationships between each EAWM index and winter temperature and precipitation over eastern China during E1 Nifio status and La Nina status are not consistent completely. So, the different reference significances of each EAWM index in El Nina status or La Nifia status should be considered carefully when used in winter climate monitoring.