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<p>This study investigates the climatic drivers and physical mechanisms for interannual variations in warm-season rainfall extremes over the Bohai Rim (BHR) region of China from 1979 to 2022. Results show that increased extreme rainfall in the BHR is primarily driven by a zonally oriented dipole circulation pattern, consisting of a barotropic western North Pacific subtropical high (WNPSH)-resembling anticyclonic anomaly to the east and a cyclonic anomaly centered south of Lake Baikal to the northwest. This configuration facilitates the convergence of cold–dry and warm–moist air masses over the region. Furthermore, it is found that El Niño-like Pacific sea surface temperature (SST) warming, which peaks in winter, exerts a significant lagged influence on subsequent warm-season BHR rainfall extremes. Elevated SST anomalies in the eastern-central equatorial Pacific during December–February are typically followed by above-normal extreme rainfall. Diagnostic analyses and model simulations reveal that this winter SST warming induces a zonal dipolar SST anomaly pattern over the Indo–western North Pacific sector in the following warm season, resulting in low-level easterly anomalies that dynamically force a prominent subtropical WNPSH-resembling anomaly gyre, together with a weakened mid-latitude cyclonic anomaly centered south of Lake Baikal. The enhanced extreme rainfall mainly results from increased tropical moisture tranport and favorable dynamic conditions associated with this anomaly gyre, with a minor contribution from the weakened cyclonic anomaly. This work highlights a major subtropical pathway linking winter Pacific SST variability to warm-season rainfall extremes in the BHR, which would provide valuable insights for seasonal prediction.</p>

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Toward drivers of the interannual variability of warm-season extreme rainfall over the Bohai Rim, China

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • Jing Wang,
  • Yongxiang Zhang,
  • Yujie Li,
  • Mingcai Li

摘要

This study investigates the climatic drivers and physical mechanisms for interannual variations in warm-season rainfall extremes over the Bohai Rim (BHR) region of China from 1979 to 2022. Results show that increased extreme rainfall in the BHR is primarily driven by a zonally oriented dipole circulation pattern, consisting of a barotropic western North Pacific subtropical high (WNPSH)-resembling anticyclonic anomaly to the east and a cyclonic anomaly centered south of Lake Baikal to the northwest. This configuration facilitates the convergence of cold–dry and warm–moist air masses over the region. Furthermore, it is found that El Niño-like Pacific sea surface temperature (SST) warming, which peaks in winter, exerts a significant lagged influence on subsequent warm-season BHR rainfall extremes. Elevated SST anomalies in the eastern-central equatorial Pacific during December–February are typically followed by above-normal extreme rainfall. Diagnostic analyses and model simulations reveal that this winter SST warming induces a zonal dipolar SST anomaly pattern over the Indo–western North Pacific sector in the following warm season, resulting in low-level easterly anomalies that dynamically force a prominent subtropical WNPSH-resembling anomaly gyre, together with a weakened mid-latitude cyclonic anomaly centered south of Lake Baikal. The enhanced extreme rainfall mainly results from increased tropical moisture tranport and favorable dynamic conditions associated with this anomaly gyre, with a minor contribution from the weakened cyclonic anomaly. This work highlights a major subtropical pathway linking winter Pacific SST variability to warm-season rainfall extremes in the BHR, which would provide valuable insights for seasonal prediction.