前、后冬的东亚冬季风年际变异及其与东亚降水的关系

INTERANNUAL VARIATION OF EAST ASIAN WINTER MONSOON IN EARLY AND LATE WINTER AND ITS RELATIONSHIP WITH EAST ASIAN PRECIPITATION

利用ERA-Interim的再分析资料和NOAA海温、降水量等资料对前、后冬的东亚冬季风的年际变异特征及其与东亚降水的关系进行对比分析,并讨论了热带和中高纬系统影响东亚冬季风变异的相对重要性。前冬的东亚冬季风变异的主导模态为东亚全区一致变异型,即一致的北风偏弱或偏强;其次为南部变异型,主要表现为在我国南方-南海北部的东北风偏弱或偏强。而后冬的东亚冬季风变异的主导模态则为南部变异型,其次为东亚全区一致变异型。从前冬到后冬,东亚冬季风的主要变异模态的次序出现交叉更替。前、后冬的冬季风主要模态以年际变化为主,但后冬主导模态还显示出冬季风有变强的趋势。前、后冬的东亚冬季风的主导变异模态也影响东亚降水异常的位置。在前冬,冬季风异常主要影响我国华北、渤海-黄海海域以及朝鲜半岛和日本南部区域的降水异常,而后冬的冬季风异常则主要导致我国东南地区及其东侧附近的西北太平洋海区的降水异常。前冬的东亚冬季风的前两种主要变异模态都受到印度洋-太平洋海温和中高纬环流系统共同的影响;后冬的东亚冬季风的前两种主要变异模态则分别主要受ENSO和中高纬系统的影响。

Based on the ERA-Interim reanalysis data and the NOAA sea surface temperature （SST） and CMAP precipitation data, the interannual variability of the East Asian winter monsoon （EAWM） in early and late winter and itsrelationshipwith the precipitation over East Asia are studied in this paper. The relative importance of tropical and mid-high latitude circulation systems for the variability of EAWM is also discussed. The first leading mode of anomalous early EAWM shows significant anomalies in the whole East Asia, meaning that strong or weak northerlies occur in the whole East Asia consistently. The second leading mode is a southern anomalous pattern with strong or weak northeasterlies over southern China and the northern South China Sea. From early winter to late winter, these first two leading modes of the EAWM appear alternatively. Although the leading modes of the early and late winter EAWMs exhibit large interannual variability, there exists an intensified trend of the monsoon in the first leading mode. The locations of large precipitation anomalies associated with the leading anomalous patterns of EAWM are different. In early winter, the variation of EAWM mainly influences the precipitation over northern China, the Bohai Sea, the Yellow Sea, the Korean Peninsula, and southern Japan. In late winter, however, the EAWM is linked to the precipitation anomalies over Southeast China and its eastern vicinity. Both tropical Indo-Pacific SST and mid-high latitude circulation systems affect the first two leading modes of the early winter EAWM significantly, but ENSO and mid-high latitude circulation systems play important roles on the first and second modes of the late winter EAWM, respectively.