Distinct tropospheric anomalies during sudden stratospheric warming events accompanied by strong and weak Ural Ridge

Abstract

Abstract Different tropospheric precursor anomalies leading to sudden stratospheric warmings (SSWs) may result in different circulation evolution. This study finds that there are distinct differences in tropospheric circulation evolutions during SSWs following anomalously strong- (SUR-SSWs) and weak- (WUR-SSWs) Ural ridge. SUR-SSWs exhibit enhanced East Asian trough in the following week, while enhanced Greenland ridge and negative tropospheric annular mode anomalies can persist for 1 month. In contrast, WUR-SSWs exhibit surface cooling over northern Eurasia without notable tropospheric annular mode anomalies. During SUR-SSWs, waves induced by the enhanced Ural wave source tend to propagate below the tropopause, amplifying the East Asian trough. Additionally, due to decreased wave phase speed, the preexisting Ural ridge anomalies migrate westward and amplify the Greenland ridge. Before WUR-SSWs, preexisting cooling over Northeast Asia migrates westward and amplifies northern Eurasia cooling. Thus, the Ural ridge anomalies prior to SSWs significantly influence post-SSW tropospheric circulation.