Winter North Atlantic tripole sea surface temperature drives following summer synchronous heat waves over Eurasia since the 2000s

Abstract Extreme high temperature events (EHTEs) that occur simultaneously across multiple regions (known as synchronous events) have a greater impact on water resources, agriculture, and ecosystems than localized events. However, the factors and mechanisms that drive synchronous EHTEs over Eurasia remain unclear. In this study, we reveal a close connection between summer EHTEs in Eastern Europe and East Asia. We show that North Atlantic tripole (NAT) sea surface temperature (SST) anomalies in the preceding winter are a key factor in the co-occurrence of summer EHTEs in these regions since the 2000s. Winter NAT SST anomalies persist into summer via air-sea interaction. The resultant North Atlantic precipitation anomalies trigger an atmospheric wave train that propagates eastwards to Eurasia, producing anticyclonic anomalies over Eastern Europe and East Asia. These anticyclonic anomalies suppress cloud cover, increase shortwave radiation and lead to synchronous summer EHTEs. Further analysis indicates that since the 2000s, the persistence of the NAT SST anomaly pattern from winter to the subsequent summer has increased. This enhances the linkage between winter NAT SST anomalies and the co-occurrence of summer EHTEs over Eurasia. Our findings advance the understanding of synchronous summer EHTEs over Eurasia and have implications for their prediction.