Unveiling the neglected driver of February 2024 compound cold-wet extremes over central China: role of the quasi-barotropic Northeast Asian anticyclone

Abstract In February 2024, Central China experienced exceptional compound cold–wet extremes (CWEs) characterized by widespread freezing rain and an unprecedented northward shift of the glaze zone. Contrary to the canonical Ural–Siberian blocking typically associated with such extremes, this event was governed by an exceptionally strong, quasi–barotropic Northeast Asian (NEA) anticyclonic anomaly (NAAA). This circulation pattern weakened the East Asian trough aloft while intensifying and shifting the Siberian High eastward at the surface. The resulting vertical coupling enhanced warm–moist advection over shallow cold air, creating a strong warm–over–cold temperature inversion ideal for CWEs and freezing rain. A self–organizing map analysis identifies the NAAA not as a transient anomaly, but as a distinct, recurrent circulation regime that historically favors stronger thermal inversions than conventional blocking patterns, and the 2024 event represents an extreme amplification of this intrinsic regime. Observations and hindcasts show external and boundary forcings explained only ∼40% of the NEA height anomaly, leaving atmospheric internal variability as the dominant driver of NAAA episodes. Specifically, North Atlantic oscillation-excited Rossby wave trains propagated eastward to amplify and sustain the NAAA. These results unveil a previously neglected dynamical pathway driving Central China compound extremes and highlight the importance of accurately capturing North Atlantic–Eurasian Rossby wave dynamics in subseasonal–to–seasonal prediction systems.