基于我国160个台站观测的月平均地面气温资料，通过考察冬季各月气温之间的联系将11月和12月划分为前冬，次年的1月至3月划分为后冬，并利用160站资料和NCEP/NCAR再分析资料，通过经验正交函数 （EOF，empirical orthogonal function）分解和依赖于季节的EOF（SEOF，season-reliant EOF）分解对近62年来我国前冬和后冬气温各自的年际变化特征、它们之间的联系以及对应的大气环流进行了分析。结果表明，我国前冬和后冬气温年际变化的前两个EOF模态在空间上均表现为全国一致的变化和南北相反的变化；其时间系数的分布表明，当前冬出现全国性偏暖（冷）或北冷（暖）南暖（冷）的气温异常时，后冬出现类似气温异常和相反气温异常的概率均在50%左右。进一步，通过SEOF分解得到了年际变化时间尺度上我国冬季气温演变的两个主要模态。第一模态（SEOF1）为前冬到后冬同相演变型，即前冬全国一致偏暖（冷）时后冬亦全国一致偏暖（冷），该模态在20世纪80年代中期有明显的年代际增暖；第二模态（SEOF2）表现为前冬到后冬反相演变型，即前冬全国一致偏冷（暖）而后冬全国一致偏暖（冷），该模态以年际变化为主。对环流场的分析表明，中纬度大气过程特别是大气遥相关型的变化是同向和反向两种演变模态产生的主要原因。SEOF1的环流表现为对流层中层斯堪的纳维亚遥相关型在整个冬季的持续性同号异常，与此相伴的海陆气压差强度和东亚高空急流强度的变化使得前、后冬中的东亚冬季风环流呈一致加强或减弱，从而引起同相演变模态。SEOF2的环流在前冬表现为欧亚遥相关型的特征，整个对流层的变化都很显著，而后冬的环流信号主要在对流层中低层显著，此时表现为类似斯堪的纳维亚遥相关型的特征且符号发生了反转，从而引起反相演变模态。
On the basis of monthly mean surface air temperature (SAT) data from 160 Chinese stations, the boreal winter is divided into early winter (ND, November and December) and late winter (JFM, January to March of the following year) by analyzing the relationship of SAT among different months. Following this definition, observational data from 160 Chinese stations, and reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) are studied by empirical orthogonal function (EOF) analysis, season-reliant EOF (SEOF) analysis, regression analysis and composite analysis to determine the interannual variations of early and late winter temperatures in China, their linkage, and related atmospheric circulations during the most recent 62 years. The first EOF modes in both early and late winter depict a pan-China temperature variation, and the second EOF modes in both early and late winter describe a temperature oscillation between northern and southern parts of China. An inspection of their corresponding principal components (PCs) indicates that if a certain SAT mode is observed in early winter, the possibility of observing the same SAT mode with the same sign in late winter is approximately 50%, which is nearly equal to that of observering the same SAT mode with the opposite sign. These results indicate that averaging the SAT for the entire winter is suitable for the former case and unsuitable for the latter case. Therefore, it is necessary to divide winter into early and later winters when the variability of wintertime SAT is investigated. To capture both the major modes of the SAT's interannual variability and the relationship between early and late winter, SEOF analysis is performed on the covariance matrix constructed with SATs from 160 Chinese stations recorded in both early and later winters. The first SEOF mode (SEOF1) captures an in-phase evolution of SAT from early to late winter. Its PC time series indicates a distinct interdecadal change in approximately the mid-1980s. The second SEOF mode (SEOF2) reflects an out-of-phase evolution of SAT from early to late winter. The corresponding PC time series is mainly featured with interannual variability. In the middle troposphere, the SEOF1 mode is closely associated with the Scandinavian teleconnection of the same sign throughout the winter, which consequently leads to changes in the intensity of the East Asian winter monsoon by altering the land-sea thermal contrast over East Asia and the intensity and the meridional location of the East Asian upper-tropospheric jet stream. In early winter, the SEOF2 mode is correlated to the Eurasian teleconnection, and the associated circulation anomalies are significant throughout the entire troposphere. In late winter, the Scandinavian-like teleconnection of the opposite phase dominates, and the significant circulation anomalies are observed only in the middle and lower troposphere. These results suggest that mid-latitude atmospheric internal dynamical processes, particularly atmospheric teleconnections, are the main causes of the formations of SEOF1 and SEOF2.
韦玮,王林,陈权亮,刘毓赟.我国前冬和后冬气温年际变化的特征与联系.大气科学,2014,38(3):524~536 WEI Wei, WANG Lin, CHEN Quanliang, LIU Yuyun. Interannual Variations of Early and Late Winter Temperatures in China and Their Linkage. Chinese Journal of Atmospheric Sciences (in Chinese),2014,38(3):524~536复制