Behaviors of Interhemispheric Coupling in Different Boreal Winter Subseasons During Major SSWs

Abstract This study utilizes 45 yrs of WACCM‐X simulations with Specified Dynamics and 22 years of Aura Microwave Limb Sounder (MLS) observations to explicitly differentiate the behaviors of interhemispheric coupling (IHC) in early, mid‐, and late winter subseasons attributed to northern hemisphere (NH) major sudden stratospheric warmings (SSWs). The typical IHC teleconnection pattern is identified in all cases and reasonable data‐model agreement is shown. The simulated residual mean circulation, parameterized gravity wave (GW) forcing, and resolved planetary and tidal forcing represent intra‐seasonal changes during NH major SSWs, which result in the different behaviors of IHCs. In particular, an anomalous cooling below the high‐latitude summer mesopause is identified in addition to the typical IHC patterns in later subseasons and attributed to the consequences of changes in residual mean circulation and GW forcing due to upwelling effects.