Dominant Modes of Interannual Variability in Atmospheric Water Vapor Content over East Asia during Winter and Their Associated Mechanisms.

Atmospheric water vapor content (WVC) is a critical factor for East Asian winter precipitation. This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and their underlying mechanisms. Based on the empirical orthogonal function (EOF) method, the leading mode (EOF1, R2 = 28.9%) of the interannual variability in the East Asian winter WVC exhibits a meridional dipole pattern characterized by opposite WVC anomalies over northeastern China and eastern China; the second mode (EOF2, R2 = 24.3%) of the interannual variability in the East Asian winter WVC exhibits a monopole pattern characterized by consistent WVC anomalies over eastern China. EOF1 is mainly modulated by two anomalous zonal water vapor transport (WVT) branches over northeastern China and eastern China, which are associated with an anomalous atmospheric wave train over Eurasia affected by sea ice cover in the Kara Sea-Barents Sea (SIC-KSBS) area in the preceding October-November (ON). EOF2 is mainly modulated by an anomalous westerly WVT branch over eastern China, which is associated with a circumglobal atmospheric zonal wave train in the Northern Hemisphere. This circumglobal zonal wave train is modulated by concurrent central and eastern tropical Pacific sea surface temperature anomalies. The SIC-KSBS anomalies in ON and the concurrent SST anomalies over tropical Pacific may partially account for the interannual variability of EOF1 and EOF2 winter WVC, and thus may provide a theoretical basis for improving the prediction of winter climate over East Asia. [ABSTRACT FROM AUTHOR]

摘要: 大气水汽含量是影响东亚地区冬季降水的重要因子. 本研究基于经验正交函数 (EOF) 方法, 分析并探讨了东亚冬季大气水汽含量年际变化的主模态及其潜在的机制. 东亚冬季水汽含量年际变化的第一模态 (EOF1, R2 = 28.9%) 表现为中国东北和华东地区反相变化的经向偶极子模态, 第二模态 (EOF2, R2 = 24.3%) 表现为中国东部上空水汽含量一致偏多/偏少的单极子模态. EOF1 主要受中国东北和华东地区上空两个纬向水汽输送异常分支调节, 前期 (10–11 月) 喀拉海-巴伦支海海冰异常通过激发横跨欧亚大陆的异常大气波列影响东亚冬季水汽含量; EOF2 主要受我国东部一个偏西的水汽输送异常分支调节, 该分支与一个环北半球纬向波列有关, 热带中东太平洋海表温度异常通过激发环北半球纬向波列影响东亚冬季水汽含量. 10–11 月喀拉海-巴伦支海海冰异常和同期热带太平洋海温异常在一定程度上解释了东亚冬季水汽含量 EOF1 和 EOF2 的年际变化, 从而为改进东亚冬季气候预报提供了理论依据. [ABSTRACT FROM AUTHOR]