Abstract
Based on observation and reanalysis datasets, numerical experiments with a simple dynamical model, and climate model outputs, this study investigates the second leading waveguide teleconnection along the summer polar front jet (PFJ) over Eurasia on the interannual time scale, the British–Okhotsk Corridor (BOC) pattern. The BOC pattern explains 20.8% of the total variance over northern Eurasia, which is only slightly lower than the first leading teleconnection, the British–Baikal Corridor pattern. It consists of four zonally oriented action centers over the British Isles, western Russia, northern Siberia, and the Sea of Okhotsk. It is primarily confined to northern Eurasia and leads to wavelike temperature and precipitation anomalies along its routine. Besides, it is occasionally coupled to the dominant waveguide teleconnection along the subtropical jet (STJ), the Silk Road pattern (SRP). A bifurcated wavelike pattern appears over Eurasia when the coupling is strong, with two branches of waves over the PFJ and the STJ, respectively. The fluctuations of the BOC–SRP linkage play a profound role in shaping the dominant climate variability modes over Eurasia. Numerical experiments with a simple dynamical model suggest that the basic flow cannot directly influence the BOC–SRP linkage by affecting the propagation condition of Rossby waves. Nevertheless, the basic flow can indirectly influence the linkage by changing the exciting locations of the BOC pattern through modulating the wave–mean flow interaction at the exit of the Atlantic jet stream. The climate model INMCM4.0 can reproduce the observed BOC–SRP linkage and its time-varying characteristics, supporting the observation and the proposed mechanism.
Significance Statement
Over Eurasia, extreme summer weather events are often related to long-lasting stagnant atmospheric circulation anomalies in the upper troposphere, which can be well determined by a few recurring modes called atmospheric teleconnections. Atmospheric teleconnections over Eurasia usually propagate along the subtropical jet (STJ) and the polar front jet (PFJ). Although the teleconnections along the STJ have been well understood, the teleconnections along the PFJ are currently not fully understood. This paper investigates the British–Okhotsk Corridor (BOC) pattern, a newly defined major summer teleconnection along the PFJ. The BOC pattern can be occasionally coupled to a dominant teleconnection along the STJ. Fluctuations of this linkage play a profound role in shaping the dominant surface climate variability modes over Eurasia. Observation and reanalysis datasets, numerical experiments with a simple dynamical model, and climate model output are used to understand this linkage in the study.
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