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<p>Warm-sector heavy rainfall is a pivotal and challenging aspect of precipitation forecasting during the rainy season in North China. It typically refers to downpours that occur on the warm side of a surface front at a distance of 200–300&#xa0;km, or within the converging airflows of southwesterly and southeasterly, and even in southwesterly without wind shear. Furthermore, such rainfall events are not influenced by tropical systems like typhoons. This study first reviews the processes associated with warm-sector heavy rainfall in North China. It is noted that these cases often involve the activity of a Back-Building Meso-scale convective system (BB-MCS). Secondly, the definition and characteristics of BB-MCS that triggers warm-sector heavy rainfall in North China are summarized. The research progress on the triggering and propagating mechanisms of BB-MCS is emphatically presented. It is pointed out that the initial convection is mainly triggered by external driving forces, which are closely related to convergence lines at boundary layer, urban heat (humid) island, wind speed fluctuations, mesoscale topography, etc. However, the back-building mechanism of MCS relies not only on external forcing but also on the up-scale development through self-organization processes, which are closely related to large-scale synoptic system, mesoscale jet stream, cold pool at boundary level and vertical shear of horizontal wind. Finally, the paper suggests several technologies and methods that warrant further exploration in this domain. Specifically, it is necessary to enhance the fine-scale detection capability of the boundary layer and delve into the detailed structural characteristics of BB-MCS under different environmental conditions. Additionally, the atmospheric anomaly method should be applied to establish predictive and early warning indicators for BB-MCS. Concurrently, the development of convective-scale model ensemble forecasting systems and conducting ensemble sensitivity analysis experiments are proposed, which are effective methods for deepening the understanding of the BB-MCS mechanism and improving its prediction accuracy.</p>

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A review of research on the mechanism of back-building MCS causing warm-sector heavy rainfall in North China

  • 期刊论文

  • 发表日期：

    2025年4月22日

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  • Nan Zhang,
  • Xiaojun Yang,
  • Jing Wang,
  • Hong Chen

摘要

Warm-sector heavy rainfall is a pivotal and challenging aspect of precipitation forecasting during the rainy season in North China. It typically refers to downpours that occur on the warm side of a surface front at a distance of 200–300 km, or within the converging airflows of southwesterly and southeasterly, and even in southwesterly without wind shear. Furthermore, such rainfall events are not influenced by tropical systems like typhoons. This study first reviews the processes associated with warm-sector heavy rainfall in North China. It is noted that these cases often involve the activity of a Back-Building Meso-scale convective system (BB-MCS). Secondly, the definition and characteristics of BB-MCS that triggers warm-sector heavy rainfall in North China are summarized. The research progress on the triggering and propagating mechanisms of BB-MCS is emphatically presented. It is pointed out that the initial convection is mainly triggered by external driving forces, which are closely related to convergence lines at boundary layer, urban heat (humid) island, wind speed fluctuations, mesoscale topography, etc. However, the back-building mechanism of MCS relies not only on external forcing but also on the up-scale development through self-organization processes, which are closely related to large-scale synoptic system, mesoscale jet stream, cold pool at boundary level and vertical shear of horizontal wind. Finally, the paper suggests several technologies and methods that warrant further exploration in this domain. Specifically, it is necessary to enhance the fine-scale detection capability of the boundary layer and delve into the detailed structural characteristics of BB-MCS under different environmental conditions. Additionally, the atmospheric anomaly method should be applied to establish predictive and early warning indicators for BB-MCS. Concurrently, the development of convective-scale model ensemble forecasting systems and conducting ensemble sensitivity analysis experiments are proposed, which are effective methods for deepening the understanding of the BB-MCS mechanism and improving its prediction accuracy.