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.