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Abstract

This study explores the physical mechanisms of the Victoria mode (VM) affecting the variations in the surface air temperature (SAT) over Eurasia and North America during the winter-spring seasons based on the reanalysis data and the numerical experiments of an atmospheric general circulation model. We find that the VM is significantly correlated with the winter-spring positive and negative SAT anomalies over the mid-to-high latitude east-central Eurasia and eastern North America, respectively. A local energy budget analysis shows that the contribution of the surface heat fluxes associated with the VM to the SAT anomalies are confined mainly to mid-to-high latitude east-central Eurasia and may not explain the formation of SAT anomalies over eastern North America. In addition, it is noted that the VM-induced anomalous atmospheric circulations play an important role in the formation of notable SAT anomalies. During winter-spring, the VM-induced negative geopotential height anomalies over the western North Pacific impose an anomalous Rossby wave source near the East Asian westerly jet core that propagates eastward, forming a wave train-like pattern. It crosses the North Pacific and reaches North America and Eurasia, leading to negative and positive SAT anomalies over eastern North America and the mid-to-high-latitude east-central Eurasia, respectively. Results from atmospheric general circulation model experiments further confirm that the spatial pattern of anomalous atmospheric circulation over the mid-to-high latitude NH caused by the VM are linked to the changes in SAT over the mid-to-high latitude Eurasia and North America.