Mid‐to‐High‐Latitude Air‐Sea Interactions Facilitate the Synchronization of the East Asian Winter Monsoon System Components

Abstract

East Asian winter monsoon (EAWM) is a powerful circulation system that profoundly influences both regional and global climate. While extensive studies have explored the factors driving the EAWM variation, recent studies reveal that the EAWM is not always an integrated system, exhibiting a notable decoupling tendency in recent decades. This underscores the need to revisit the mechanisms changing the EAWM components' coherence from a hemispheric perspective. Focusing on the co‐variations between the two key EAWM components of East Asian trough (EAT) and Siberian High (SH), and combining the analyses on observations/reanalysis, atmospheric general circulation model simulations, and fully‐coupled climate model simulations, this study reveals that the in‐phase EAT‐SH variation primarily results from the air‐sea interaction over the Northern Hemisphere mid‐to‐high latitudes. The critical sea surface temperature (SST) anomaly pattern is featured by significant western North Pacific SST anomalies, a zonal tripole SST pattern over the North Atlantic‐Mediterranean Sea, and the Barents‐Kara Sea SST anomalies. In contrast, the out‐of‐phase EAT‐SH variation is not sufficiently explained by the SST anomalies. Instead, it is optimally related to atmospheric dynamical processes, featuring an overall Arctic Oscillation‐like pattern alongside an equivalent‐barotropic tripole atmospheric pattern over the Asian continent. Furthermore, owing to these distinct climate dynamics, the two EAT‐SH configurations exhibit different lagged climatic influence. Only the in‐phase EAT‐SH variation is associated with greater 1‐month persistence of climatic anomalies over East Asia, compared with the out‐of‐phase configuration.