Synergistic Dynamics of Large-scale Three-dimensional Circulations in Two Types of East Asian Cold Events

Traditional studies on East Asian cold events have predominantly focused on the impacts of large-scale horizontal circulation characteristics. Differently, this paper uses the three-pattern decomposition of the global atmospheric circulation (3P-DGAC), classifying East Asian cold events into wave-train type and blocking type based on their dominant three-dimensional (3D) circulation patterns. The wave-train type is related to an upper-tropospheric Rossby wave train that originates in the North Atlantic and propagates eastward across the Eurasian continent. While the blocking type is associated with a subpolar blocking that originates in the North Pacific and retrogresses westward into the eastern Siberia. Corresponding to the persistent widespread anticyclonic circulation anomaly of the blocking type, the surface Siberia High (SH) and subsequent cooling tend to be more intense and last longer. Before the cold peak, both types exhibit a positive meridional circulation anomaly over the mid-latitude East Asia (EA), and a negative zonal circulation anomaly over the northern EA, which together strengthen the SH and facilitate the transportation of cold air. Especially, the local Brewer-Dobson (BD) circulation in the blocking type developed vigorously, triggering the negative phase of the stratospheric Arctic Oscillation to propagate downward and influence tropospheric weather. This study clarifies the synergistic dynamics of large-scale 3D circulations, emphasizing the potential of vertical circulation patterns to improve cold event predictability and providing new insights into the dynamics of East Asian cold events.