衡阳市暴雨天气学分型及特征分析

Analysis on the Classification and Characteristics of Heavy Rain in Hengyang

摘要: 利用2009~2019年常规气象观测资料、NCEP 1˚ × 1˚逐6小时再分析资料，根据湖南省的暴雨预报经验与方法，对衡阳69例暴雨过程进行天气学分型，分析物理量场等特征。结果表明：1) 衡阳地区暴雨天气可分为5大类：低涡切变型、风速辐合型、东风气流型、台风型和对流型暴雨。低涡切变型根据风向切变的特征又可分为冷式切变型和暖式切变型，冷式与暖式切变型可互相转化，风速辐合型根据影响的风向不同，可分为南风和东北风辐合切变型。2) 低涡切变型为出现暴雨频率最高的类型，出现次数为49次，其中冷式切变型出现34次、暖式切变型出现15次，其次为风速辐合型，出现次数为15次，南风辐合型出现12次、东北风辐合型出现3次，出现频率最低的为对流型暴雨和东风气流型暴雨，均出现1次，台风型暴雨出现3次。3) 在影响衡阳降水的天气系统中，大气中层很多时候没有明显的槽脊，环流较平直但多小波动，700 hPa的西南急流也不是必要条件，地面多数时候有辐合线或处于辐合中心，一定的湿层厚度为衡阳地区出现暴雨的必要条件，湿层至少要达到大气平均层(600 hPa)以上，大气低层的水汽辐合、中低层较强的垂直上升速度以及涡度场，为衡阳出现暴雨天气的重要参考依据。

Abstract: Based on the conventional meteorological observation data from 2009 to 2019 and the NCEP 1˚ × 1˚ 6-hour reanalysis data, according to the experience and method of heavy rain forecast in Hunan province, the weather classification of 69 heavy rain processes in Hengyang was carried out to analyze the characteristics of physical quantity field. The results show that: 1) the heavy rain in Heng-yang area can be divided into five categories: low vortex shear type, wind speed convergence type, east wind flow type, typhoon type and convective type. According to the characteristics of wind di-rection shear, the low vortex shear type can be divided into cold shear type and warm shear type. The cold shear type and warm shear type can be converted to each other. The wind speed convergence type can be divided into south wind and northeast wind convergence shear type according to the different wind direction affected. 2) Low vortex, and for the most heavy rain type occurrences for 49 times, which cooled cutting variant appear 34 times, warm, and a 15 second type for wind speed convergence, occurrences of 15 times, south wind convergence appears 12 times, northeaster convergence appeared three times, the lowest frequency for convection type heavy rain and dongfeng airflow type torrential rain. All of them had one heavy rain and three typhoon-type heavy rains. 3) In the weather system affecting Hengyang precipitation, there is no obvious trough ridge in the middle atmosphere many times, the circulation is flat but more small fluctuations, the southwest jet 700 hPa is not a necessary condition, the ground most of the time there is a convergence line or in the convergence center, a certain thickness of wet layer is the necessary condition for the occurrence of heavy rain in Hengyang. The wet layer should at least reach the atmospheric average layer (600 hPa) above, the water vapor convergence in the lower layer of the atmosphere, the strong vertical rising speed and vorticity field in the middle and lower layer, for Hengyang heavy rain weather is an important reference basis.