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2025年7月下旬华北特大暴雨基本特征及成因初探

Basic characteristics and preliminary causes of the extreme rainstorm over North China in late July 2025

  • 摘要: 利用常规高空和地面观测、FY-4B卫星、天气雷达及ERA5再分析等资料,分析了2025年7月23—29日华北特大暴雨的实况特征和基本天气学成因。结果表明:此次过程降水持续时间长,降水强度和累计降水量大,具有一定极端性;降水空间分布呈“双雨带、多中心”,暖区暴雨特征突出,降雨阶段性和夜雨特征明显。中高纬度平直锋区、西北太平洋副热带高压(以下简称“副高”)及其南侧多台风之间形成稳定的形势场,为持续性强降水提供了有利的天气尺度背景;三个台风外围远距离水汽接力输送造成的边界层水汽辐合,是其重要的水汽来源。26—27日暖区暴雨发生在天气尺度低空急流减弱背景下,由多个β中尺度对流云团引发。后向传播和系统走向与移向高度重合产生的“列车效应”,是短时强降水维持较长时间的重要原因;冷池-暖湿舌(或暖脊)作用及中尺度锋区维持,是对流触发和再组织的关键中尺度作用机制,山前偏南气流辐合亦增强了对流发展,是导致密云等山区极端强降水的关键因素。

     

    Abstract: This study investigates the extreme rainstorm over North China during 23–29 July 2025 using surface and upper-air observations, FY-4B satellite data, radar data, and ERA5 reanalysis data. The event was characterized by a long duration, high intensity, and large accumulated precipitation, exhibiting a spatial pattern of “double rainbands with multiple centers” and marked warm-sector features. A stable synoptic background formed by a mid–high-latitude straight frontal zone, the northward extension of the western North Pacific subtropical high, and multiple typhoons favored the prolonged rainfall. Relayed moisture transport along typhoon peripheries provided abundant water vapor. Warm-sector rainstorms on 26–27 July were sustained by mesoscale β convective systems.The “train effect”, associated with the backward propagation of convective cells and the strong alignment between the orientation and movement direction of the convective system, was a key factor contributing to the longevity of short-term heavy precipitation. Mesoscale processes, including the interactions beteween the cold pool and warm-moist tongue, mesoscale front maintenance, and low-level southerly convergence along the mountain front, further promoted convective initiation and organization.

     

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