Enhanced Influence of Tropical Pacific Sea Surface Temperature Anomalies on Spring Extreme Heat Events Over Mid-High Latitude Eurasia

This study presents an interdecadal enhancement in the interannual relationship between spring extreme heat events (EHEs) over mid-high latitude Eurasia and winter sea surface temperature (SST) over the tropical central-eastern Pacific (TECP) after the late 1990s. Comparative analyses of the two subperiods before and after the late 1990s show that the interdecadal changes in the winter TECP SST could be responsible for such changeable relationship. After the late 1990s, the winter TECP SST anomalies (SSTA) feature a central Pacific (CP)-type pattern. The CP-type SSTA cause an anticyclone anomaly over the North Atlantic through the Pacific-North American-like teleconnection, further leading to a dipole SST pattern over the tropical to mid-latitude North Atlantic. The CP-type SSTA and North Atlantic dipole SSTA persist well from winter to spring, and the North Atlantic dipole SSTA favor the propagation of the CP-type SST-excited Rossby wave train to Eurasia in spring. Therefore, the TCEP SSTA have a significant interannual relationship with the spring Eurasian atmospheric circulations and EHEs after the late 1990s. The above physical processes are further confirmed by the SSTA sensitivity numerical experiments. In contrast, before the late 1990s, the winter TECP SSTA show an eastern Paci?c-type pattern, which is related to weak and insignificant North Atlantic SSTA and spring Eurasian atmospheric circulations; consequently, the TCEP SSTA have a weak relationship with the EHEs variations during this period. The TCEP SSTA with one season leading can provide valuable information for the prediction of spring Eurasian EHEs variations in the recent two decades.