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<p>Based on hourly precipitation, temperature, and wind observations, alongside ERA5 reanalysis data from the summers (June–August) of 2020–2025 in the Shenyang urban area, this study classifies and analyzes the characteristics and causes of Heavy Rain Events (HREs). The non-hydrostatic mesoscale WRF model was employed to conduct numerical simulations and sensitivity experiments on typical events. High-resolution simulation outputs were utilized to investigate the impact of urban effects on HREs under weak weather backgrounds. The results indicate that HREs under weak weather backgrounds typically lasted less than two hours, with 74% occurring in the afternoon, exhibiting a distinct characteristic of sudden onset. In these events, Hourly Heavy Rainfall (HHR) showed significant localized characteristics, particularly concentrated near the urban center. Notably, the thermal and relative humidity conditions in the urban center showed no strong spatial correspondence with the concentrated areas of HHR near the city center. Analysis of wind field observations and numerical simulations revealed that under weak weather backgrounds, the high roughness of the urban canopy in central Shenyang decelerates the windward airflow, causing accumulation and convergence, and enhancing vertical upward motion, which facilitates the intensification of precipitation. This system, which precedes the onset of heavy rain, generates localized upward motion that may serve as a critical dynamical factor triggering small- to meso-scale systems of localized heavy rain in the urban center area.</p>

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City-induced wind blockage effect on heavy rain events under weak weather backgrounds

  • 期刊论文

  • 发表日期：

    2026年5月21日

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  • Q. Yan,
  • Z. Zhao,
  • H. Jiao

摘要

Based on hourly precipitation, temperature, and wind observations, alongside ERA5 reanalysis data from the summers (June–August) of 2020–2025 in the Shenyang urban area, this study classifies and analyzes the characteristics and causes of Heavy Rain Events (HREs). The non-hydrostatic mesoscale WRF model was employed to conduct numerical simulations and sensitivity experiments on typical events. High-resolution simulation outputs were utilized to investigate the impact of urban effects on HREs under weak weather backgrounds. The results indicate that HREs under weak weather backgrounds typically lasted less than two hours, with 74% occurring in the afternoon, exhibiting a distinct characteristic of sudden onset. In these events, Hourly Heavy Rainfall (HHR) showed significant localized characteristics, particularly concentrated near the urban center. Notably, the thermal and relative humidity conditions in the urban center showed no strong spatial correspondence with the concentrated areas of HHR near the city center. Analysis of wind field observations and numerical simulations revealed that under weak weather backgrounds, the high roughness of the urban canopy in central Shenyang decelerates the windward airflow, causing accumulation and convergence, and enhancing vertical upward motion, which facilitates the intensification of precipitation. This system, which precedes the onset of heavy rain, generates localized upward motion that may serve as a critical dynamical factor triggering small- to meso-scale systems of localized heavy rain in the urban center area.