Coherent Interannual Variations of Springtime Surface Temperature and Temperature Extremes Between Central-Northern Europe and Northeast Asia

摘要

This study reveals a strong coherent interannual variation in spring surface air temperature (SAT) and temperature extremes between central-northern Europe (45-70 degrees N, 0-30 degrees E) and Northeast Asia (40-70 degrees N, 110-140 degrees E). The regional mean spring SAT over the two regions is highly correlated, with a correlation of 0.6 during 1950-2017. Arctic Oscillation (AO) and an atmospheric teleconnection, termed the North Atlantic-Eurasian (NAE) pattern, both play important roles in connecting SAT anomalies over the two regions. Anticyclonic anomalies are seen over central-northern Europe and Northeast Asia during positive phases of the spring AO and NAE teleconnections. The associated southerly and westerly wind anomalies to the northwestern side of the anomalous anticyclones lead to surface warming over the two regions via anomalous wind-induced heat advection from lower latitudes. In addition, a decrease in cloud cover and an accompanying increase in surface downward shortwave radiation also contribute to the coherent SAT warming over central-northern Europe and Northeast Asia. We suggest that synoptic-scale eddies forcings are crucial to the maintenance of the spring NAE teleconnection. Atmospheric model experiments indicate that the North Atlantic sea surface temperature anomalies also partly contribute to the maintenance of the NAE-related atmospheric anomalies over the North Atlantic and European regions. The observed coherent spring SAT variations over central-northern Europe and Northeast Asia and their associations with the AO and midlatitude atmospheric teleconnections can be reproduced in the long historical simulation of a coupled model. This study has implication for the understanding of concurrent occurrence of extreme temperature events over different regions of Eurasia.