On 8–11 August 2022, South Korea experienced a catastrophic heavy rainfall event (HRE) with 14 fatalities. To elucidate its driving mechanisms, the present study performs a multiscale analysis by hierarchically delineating the synoptic and large-scale characteristics of the HRE. Its synoptic condition was featured by the confrontation of the western North Pacific subtropical high and the continental cyclone in the north of the Korean Peninsula. At their interface, a tremendous amount of moisture was transported in an elongated shape (i.e., atmospheric river) along with strong frontogenetic activity. This provided a favorable environment for potential instability. The continental cyclone was maintained throughout the HRE period, while a transient cyclone was superposed contributing to more intense rainfall in the early stage of the HRE. This persistent cyclone in the north of the Korean Peninsula originated from a far-upstream-originated cutoff low that became a part of the quasi-stationary wave train along the Asian subtropical jet. A linear model experiment suggests that the quasi-stationary wave train was excited by the enhanced tropical convection related to the boreal summer intraseasonal oscillation. The anomalously strong subtropical jet also acted as an effective waveguide. These results suggest that the integration of synoptic and large-scale processes is essential to understand this unprecedented HRE.

中文翻译：

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2022 年 8 月上旬韩国灾难性强降雨事件的多尺度驱动因素


2022 年 8 月 8 日至 11 日，韩国经历了灾难性强降雨事件 (HRE)，造成 14 人死亡。为了阐明其驱动机制，本研究通过分层描述神罗的天气和大尺度特征来进行多尺度分析。其天气状况以西北太平洋副热带高压与朝鲜半岛北部大陆气旋对峙为特征。在它们的界面处，大量的水分以细长的形状（即大气河）输送，同时伴随着强烈的锋生活动。这为潜在的不稳定提供了有利的环境。大陆气旋在整个 HRE 期间持续存在，而短暂气旋的叠加导致 HRE 早期降雨更加强烈。朝鲜半岛北部的持续气旋起源于上游遥远的截止低压，该低压成为亚洲副热带急流沿线准静止波列的一部分。线性模型实验表明，准稳态波列是由与北方夏季季节内振荡相关的热带对流增强所激发的。异常强烈的副热带急流也起到了有效的波导作用。这些结果表明，天气和大规模过程的整合对于理解这个前所未有的神圣罗马帝国至关重要。