The collaborative relationship among members of the East Asian winter monsoon (EAWM) system is first examined through the multivariate EOF (MV-EOF). Univariate EOF is then used to define the intensity index of each single system. Based on the above analyses, an integrated index of the East Asian winter monsoon (EAWMII) is defined. The new index exhibits distinct interannual variability and takes into account variations of Siberian high, East Asian trough, and meridional shear of upper-tropospheric zonal wind. Results show that the EAWMII can capture well the continuous weakening of the EAWM since the mid-1980s. It is also statistically significantly correlated with variations of both atmospheric circulation fields and surface temperature during winter. In addition, the EAWMII is closely related to the Arctic Oscillation (AO) index, the Nino3.4 sea surface temperature index, and the North Pacific Oscillation (NPO) index. The impact of AO on the East Asian surface temperature primarily occurs in the middle and high latitudes of Eurasia, Northeast China, and North Japan, etc. The influence of NPO is mainly registered in South China, East China, North Korea, South Korea, and South Japan. It is very likely that the AO affects the EAWM via the NPO.%本文通过多变量经验正交函数展开(multivariate EOF,简称MV-EOF)研究了东亚冬季风各系统成员的协同关系,再运用单变量EOF定义单个系统的强度系数.从而给出能够反映东亚冬季风各主要特征及其年际变化、同时包含西伯利亚高压、东亚大槽和纬向风经向切变信息的强度指数(EAWMII).分析表明,这个新指数EAWMII能够很好地反映东亚冬季风在20世纪80年代中期的减弱信号,并且与大气环流场以及东亚冬季表面温度的变化均显著相关,能够在很大程度上表征东亚冬季风的综合特征.此外,EAWMII与北极涛动(Arctic Oscillation,简称AO)指数、北太平洋涛动(North Pacific Oscillation,简称NPO)指数和Ni(n)o3.4指数相关显著.分析还表明AO和NPO影响东亚冬季气候的区域有所不同:AO主要影响欧亚大陆中、高纬、我国东北以及日本北部等地区,NPO则主要影响华南、华东、朝鲜、韩国以及日本中南部及其附近海域.并且,AO很可能可以通过影响NPO进而影响东亚冬季风.
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