Influence of Major Stratospheric Sudden Warming on the Unprecedented Cold Wave in East Asia in January 2021

Abstract An unprecedented cold wave intruded into East Asia in early January 2021 and led to record-breaking or historical extreme low temperatures over vast regions. This study shows that a major stratospheric sudden warming (SSW) event at the beginning of exerted an important influence on this wave. The SSW occurred 2 subsequently displacement polar vortex Asian side. Moreover, induced signal propagate downward mid-to-lower troposphere, which not only enhanced blocking Urals–Siberia region negative phase Arctic Oscillation, but also shifted tropospheric off pole. displaced vortex, Ural blocking, another downstream ridge western North America formed distinct inverted omega-shaped circulation pattern (IOCP) Asia–North Pacific sector. IOCP was most direct impactful atmospheric causing Asia. triggered meridional cell with upward branch Siberia. intensified Siberian high low-level northerly winds, favored invasion Hence, circulations such as IOCP, high, eastward propagation Rossby eventually outbreak 2021.