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<p>Extreme cold surges over northern Eurasia can be attributed to the intraseasonal variability of Arctic stratospheric polar vortex (SPV). The shift of the SPV toward Eurasia (EUR-shift), one of the remarkable SPV variations, is always driven by the increased tropospheric planetary waves propagated into the stratosphere, which are triggered by the reinforcement of northern European blocking. However, it is not resolved when and how the tropospheric planetary-scale teleconnection pattern across the Eastern Hemisphere, rather than regional signals, can affect the EUR-shift occurrence from the perspective of stratosphere-troposphere coupling. This study based on ERA5 reanalysis data and WACCM simulations indicates that the tropospheric circulation anomalies prior to EUR-shift events closely resemble the positive-phase Scandinavian (SCA) teleconnection pattern, accompanied by the intensification of stratospheric planetary wave activities over Siberia. There are distinct differences in vertical wave propagation characteristics and associated spatial distribution of stratospheric potential vorticity (PV) anomalies preceding EUR-shift events with (SCA-EUR-shift) and without (nonSCA-EUR-shift) positive SCA states. In contrast to comparatively weak stratospheric response of nonSCA-EUR-shift events, SCA-EUR-shift events tend to force anomalously active tropospheric wavenumber-1 planetary waves into the lower stratosphere and resultant positive stratospheric PV anomalies over Siberia, ultimately contributing to the formation of strong EUR-shift pattern. Additionally, the risk of EUR-shift is significantly and substantially elevated under positive SCA conditions within a lead time of 6 days, and the causal relationship therein further underscores the dynamical mechanism of tropospheric drivers impacting stratospheric variability. Thus, the positive SCA pattern acts as a vital tropospheric precursor to the movement of the SPV toward Eurasia.</p>

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Scandinavian teleconnection pattern favors the shift of Arctic stratospheric polar vortex toward Eurasia

  • 期刊论文

  • 发表日期：

    2025年8月18日

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  • Chuntao Zou,
  • Ruonan Zhang,
  • Fei Huang

摘要

Extreme cold surges over northern Eurasia can be attributed to the intraseasonal variability of Arctic stratospheric polar vortex (SPV). The shift of the SPV toward Eurasia (EUR-shift), one of the remarkable SPV variations, is always driven by the increased tropospheric planetary waves propagated into the stratosphere, which are triggered by the reinforcement of northern European blocking. However, it is not resolved when and how the tropospheric planetary-scale teleconnection pattern across the Eastern Hemisphere, rather than regional signals, can affect the EUR-shift occurrence from the perspective of stratosphere-troposphere coupling. This study based on ERA5 reanalysis data and WACCM simulations indicates that the tropospheric circulation anomalies prior to EUR-shift events closely resemble the positive-phase Scandinavian (SCA) teleconnection pattern, accompanied by the intensification of stratospheric planetary wave activities over Siberia. There are distinct differences in vertical wave propagation characteristics and associated spatial distribution of stratospheric potential vorticity (PV) anomalies preceding EUR-shift events with (SCA-EUR-shift) and without (nonSCA-EUR-shift) positive SCA states. In contrast to comparatively weak stratospheric response of nonSCA-EUR-shift events, SCA-EUR-shift events tend to force anomalously active tropospheric wavenumber-1 planetary waves into the lower stratosphere and resultant positive stratospheric PV anomalies over Siberia, ultimately contributing to the formation of strong EUR-shift pattern. Additionally, the risk of EUR-shift is significantly and substantially elevated under positive SCA conditions within a lead time of 6 days, and the causal relationship therein further underscores the dynamical mechanism of tropospheric drivers impacting stratospheric variability. Thus, the positive SCA pattern acts as a vital tropospheric precursor to the movement of the SPV toward Eurasia.