Interdecadal variation in atmospheric water vapour content over East Asia during winter and the relationship with autumn Arctic sea ice

This study focused on the interdecadal variability in water vapour content (WVC) over East Asia during winter and its associated mechanisms. The interdecadal variation in the WVC over East Asia during winter was investigated using the empirical orthogonal function (EOF) method. The leading mode (EOF1, explained variance is 52.7%) of interdecadal variability in the WVC, which explains most of the interdecadal variation, exhibits a monopole pattern characterized by consistent WVC anomalies over East Asia. The mechanisms associated with the interdecadal variability in winter WVC over East Asia were further investigated, and it was found that the interdecadal variability in winter WVC over East Asia is modulated by three water vapour transport (WVT) branches from the eastern, western, and southern boundaries of East Asia that are associated with Eurasian winter circulation. Further analyses revealed that increased sea ice concentration over the Barents-Kara Sea (SIC-BKS) in October-November (ON) serves as the source of wave activity flux and stimulates a stationary wave train along the Eurasian continent to change the downstream atmospheric circulation. As a response, an abnormal cyclone, an abnormal anticyclone, and an abnormal cyclone are triggered over western Siberia, the northern area of East Asia, and the southern area of East Asia, which are together favourable for WVC sufficiency over East Asia. Sensitivity experiments by the Community Atmosphere Model, version 4 (CAM4) using sea ice forcing in the Barents Sea yield similar results to the observed data, further confirming our conclusion. Therefore, the SIC-BKS in ON may be an important potential predictor for the interdecadal variability in winter WVC over East Asia.