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<p>As one of the major sources of planetary waves, the Tibetan Plateau and the Mongolian Plateau have strong topographic effects on the upward wave propagation from the troposphere to the stratosphere and, thus, the stratospheric polar vortex (SPV). Conducting numerical simulations by the stratosphere-resolved WACCM4 model, we design seven sets of terrain sensitivity experiments and simulate the circulation changes induced by the East Asian (EA) topographic height reduction process from the control condition (CTL) to 500&#xa0;m. Results show that the response of the SPV intensity and spatial distribution to decreasing topographic height is nonlinear. Specifically, the SPV intensity tends to strengthen above 3000&#xa0;m and from 1500&#xa0;m to 500&#xa0;m, whereas the weakening of the SPV occurs from 3000&#xa0;m to 1500&#xa0;m. Such a non-monotonic behavior of SPV possesses an intimate relationship with the airflow transitions from bypassing to climbing effects, the alteration of tropospheric circulation patterns, and the evolution of upward planetary waves. By decomposing planetary waves into wave-1 and wave-2 components, this study reveals that wave-1 contributes more significantly throughout the whole EA height reduction process than wave-2, leading to a higher frequency of Displaced sudden stratospheric warming (SSW) events. Notably, the evolution of the Displaced SSW frequency closely follows the nonlinear response of the SPV intensity. The findings offer new insights by systematically examining the effects of gradual EA height reduction, filling a gap between full-topography versus non-topography frameworks.</p>

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Dynamical effects of East Asian topography on the northern hemisphere stratospheric polar vortex in winter

  • 期刊论文

  • 发表日期：

    2025年10月17日

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  • Qinlan Yang,
  • Yueyue Yu,
  • Xin Xia,
  • Rongcai Ren,
  • Dong Guo

摘要

As one of the major sources of planetary waves, the Tibetan Plateau and the Mongolian Plateau have strong topographic effects on the upward wave propagation from the troposphere to the stratosphere and, thus, the stratospheric polar vortex (SPV). Conducting numerical simulations by the stratosphere-resolved WACCM4 model, we design seven sets of terrain sensitivity experiments and simulate the circulation changes induced by the East Asian (EA) topographic height reduction process from the control condition (CTL) to 500 m. Results show that the response of the SPV intensity and spatial distribution to decreasing topographic height is nonlinear. Specifically, the SPV intensity tends to strengthen above 3000 m and from 1500 m to 500 m, whereas the weakening of the SPV occurs from 3000 m to 1500 m. Such a non-monotonic behavior of SPV possesses an intimate relationship with the airflow transitions from bypassing to climbing effects, the alteration of tropospheric circulation patterns, and the evolution of upward planetary waves. By decomposing planetary waves into wave-1 and wave-2 components, this study reveals that wave-1 contributes more significantly throughout the whole EA height reduction process than wave-2, leading to a higher frequency of Displaced sudden stratospheric warming (SSW) events. Notably, the evolution of the Displaced SSW frequency closely follows the nonlinear response of the SPV intensity. The findings offer new insights by systematically examining the effects of gradual EA height reduction, filling a gap between full-topography versus non-topography frameworks.