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<p>Based on meteorological observational datasets covering 1981–2024, this study systematically examines the spatiotemporal characteristics, key spring precursors and underlying physical mechanisms of summer extreme precipitation over Southwest China (SWCSEP), and constructs a physical mechanism-based empirical (P-E) seasonal prediction model. The results show that SWCSEP is dominated by interannual variability, with a prominent decadal shift around 1999, accompanied by a significant eastward displacement of key interannual circulation systems over Eurasian mid-high latitudes. On the interannual scale, SWCSEP is jointly regulated by two independent spring precursors from mid-high to low latitudes, namely the meridional tripole snowmelt mode over Eurasia and equatorial central Pacific sea surface temperature variability (SSTV). Eurasian snowmelt anomalies could excite summer mid-high latitude anomalous wave trains through the soil moisture memory effect, while April–May tropical Pacific SSTV is linked to basin-wide warming in the Indian Ocean, which may further modulate the Western Pacific Subtropical High via tropical circulation adjustments. The synergy of these two forcings contributes to the convergence of cold and warm advection and abundant water vapor transport over Southwest China, favoring the occurrence of extreme precipitation events. The P-E model built on these physical linkages exhibits robust performance in the independent forecast period, providing effective scientific support for regional extreme precipitation disaster prevention and mitigation.</p>

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Spring Eurasian snowmelt and tropical Pacific SST variability as key predictors for summer extreme precipitation over Southwest China

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • Zhiheng Chen,
  • Zongjian Ke,
  • Daquan Zhang,
  • Chao Wang,
  • Liping Zeng

摘要

Based on meteorological observational datasets covering 1981–2024, this study systematically examines the spatiotemporal characteristics, key spring precursors and underlying physical mechanisms of summer extreme precipitation over Southwest China (SWCSEP), and constructs a physical mechanism-based empirical (P-E) seasonal prediction model. The results show that SWCSEP is dominated by interannual variability, with a prominent decadal shift around 1999, accompanied by a significant eastward displacement of key interannual circulation systems over Eurasian mid-high latitudes. On the interannual scale, SWCSEP is jointly regulated by two independent spring precursors from mid-high to low latitudes, namely the meridional tripole snowmelt mode over Eurasia and equatorial central Pacific sea surface temperature variability (SSTV). Eurasian snowmelt anomalies could excite summer mid-high latitude anomalous wave trains through the soil moisture memory effect, while April–May tropical Pacific SSTV is linked to basin-wide warming in the Indian Ocean, which may further modulate the Western Pacific Subtropical High via tropical circulation adjustments. The synergy of these two forcings contributes to the convergence of cold and warm advection and abundant water vapor transport over Southwest China, favoring the occurrence of extreme precipitation events. The P-E model built on these physical linkages exhibits robust performance in the independent forecast period, providing effective scientific support for regional extreme precipitation disaster prevention and mitigation.