高空西北气流下贵州铜仁特大暴雨的成因分析

本文利用NCEP 1°×1°逐6 h再分析资料和地面区域自动站逐小时观测资料，对贵州省铜仁市梵净山东侧2020年6月29日夜间的一次特大暴雨天气过程的大尺度环流背景和中尺度天气系统进行了分析。结果表明：此次暴雨过程处于高空西北气流控制背景下，中低层动力抬升条件较弱，但深厚的暖云层和湿层、较低的自由对流高度（LFC）、抬升凝结高度（LCL）和中等到强的对流有效位能（CAPE），配合低层水汽辐合抬升运动的爆发性增强有利于此次梵净山东侧高效率降水。暴雨落区分为A区和B区两个区域，其间降雨特征存在明显不同，A区降水开始时间早，累计雨量大，主要为偏东北风与偏东南风辐合引起的上升运动造成的对流性降水，而B区小时雨强更大，由于小尺度涡旋的发生发展、配合低层弱冷空气的抬升触发作用造成的冷性降水；且降水强度与1h正变压、负变温呈正相关关系。迎风坡和喇叭口地形的动力强迫抬升作用，利于低层水汽输送和抬升凝结，受近地层东北气流与东南偏南气流形成的中尺度辐合线触发、加强，也是此次极端暴雨形成的重要原因。

An Analysis of the Causes of the Extreme Rainstorm in Tongren, Guizhou under the Northwest Airflow

This paper uses NCEP 1°×1° to analyze the data 6 hours by 6 hours and the hour by hour observation data from the surface area automatic station to analyze the large-scale circulation background of a heavy rainstorm on the night of June 29, 2020, on the east side of Fanjing, Tongren City, Guizhou Province. And the mesoscale weather system was analyzed. The results showed that the heavy rain was under the control of the high-altitude northwest airflow, and the mid-low-level dynamic uplift conditions were weak, but the deep warm clouds and wet layers, low LFC and LCL, and medium to strong CAPE values, combined with the explosive enhancement of low-level water vapor convergence and uplift movement, is conducive to the high-efficiency precipitation on the east side of Fanjing. The rainstorm is divided into two areas: Area A and Area B. There are obvious differences in rainfall characteristics. Area A precipitation starts early and the accumulated rainfall is large. It is mainly convective precipitation caused by the upward movement caused by the convergence of northeast and southeast winds. While the hourly rain is greater in Zone B , due to the occurrence and development of small-scale vortices, and the cold precipitation caused by the uplift of the weak cold air at the lower level; And the precipitation intensity is positively correlated with the 1h positive variable pressure and negative variable temperature .The dynamic forced uplift of the windward slope and the topography of the bell mouth is conducive to the transportation and uplift of low-level water vapor. It is triggered and strengthened by the mesoscale convergence line formed by the northeast airflow and the southeast airflow near the surface. It is also an important reason for the formation of extreme rainstorms.