Enhanced spring warming of the Tibetan Plateau amplifies summer heat stress in Eastern Europe

Abstract

AbstractThe Tibetan Plateau (TP), often referred to as the “Roof of the World”, has experienced rapid warming in recent decades. This warming has had significant impacts on downstream regions, while its effects on upstream regions are less well-defined. This study explores the relationship between TP warming and the occurrence of summer heat stress days in Europe, with a particular focus on Eastern Europe (EEU). Our analysis reveals a robust correlation between TP warming in both the summer and the preceding spring, and the frequency of heat stress days in EEU, demonstrating a significant interannual connection. During the spring, pronounced warming in the southern TP generates a strong local Rossby wave source, triggering a substantial divergence anomaly that amplifies the warming effect. This mechanism weakens the subtropical jet and strengthens the polar jet during the summer, setting the stage for anticyclonic anomalies over EEU. Furthermore, anomalies induced by TP warming, characterized by local upward movement and divergence at upper levels, intensify convergence and sinking airflow in the upstream region, leading to increased adiabatic heating in EEU. The dynamic response of the summer circulation anomaly, exemplified by the anticyclone anomaly over EEU, to prior TP warming is further corroborated through numerical simulations.