Synchronized heat extremes over Western Europe and the Yangtze-Huai river basin during summer 2025

Abstract

Western Europe and the Yangtze–Huai River Basin experienced two exceptional synchronized extreme heat events during the summer of 2025, providing a unique opportunity to investigate the mechanisms linking geographically distant heat extremes. Because the two events exhibit similar large-scale dynamical evolution, the first event is examined in detail to illustrate the underlying processes. Linear Baroclinic Model experiments reveal that the associated Rossby wave train is triggered by thermal anomalies whose dominant forcing migrates progressively eastward from western North America to western Asia. The synchronized extreme heat events in western Europe and Yangtze–Huai River Basin are stronger, broader, and more persistent, which are mainly produced by strong, large and persistent anticyclonic anomalies of Rossby wave trains due to weaker mean upper-level potential vorticity gradients and enhanced upstream westerlies. These findings provide new insights into the development and persistence of synchronized heat extremes, with potential implications for their sub-seasonal prediction.