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湖北省短时强降水雨团的识别及分类特征研究

Research on rain cell identification and classification characteristics of short-duration heavy precipitation in Hubei Province

  • 摘要: 短时强降水是湖北省主要灾害性天气之一,精准识别短时强降水雨团并研究其分类特征,对提升短时强降水预警能力有重要意义。本研究基于2020—2024年湖北省气象观测站和全国天气雷达组网拼图数据,采用八连通链码法和时空重叠法识别追踪短时强降水雨团,依据雨团移动特性和影响区域,将其分为静止型和四类移动型(东部型、西南型、西北型、全省型),并对比分析了不同类型短时强降水雨团的空间活动规律及参数特征。结果显示:(1) 共识别出4 455次短时强降水过程,雨团源地主要位于湖北省东部平原与山地过渡带,活动区域集中在湖北省中东部。(2) 静止型占比最高(86%),持续时间最短(约1.5 h),影响范围最小(568 km2);全省型占比最低(1%),持续时间最长(约16 h),影响范围最大(约30 000 km2);其他类型的时空特性介于两者之间。(3) 不同类型短时强降水雨团的几何特征不同:静止型水平形状近方形、空间形态偏“瘦高”,全省水平形状偏细长、空间形态偏“矮胖”,其他类型的几何形态介于两者之间;雨团的雨顶高度均超10 km,西北型最高(11.53 km),西南型最低(10.8 km)。(4) 湖北省短时强降水雨团强降水以低质心为主,40 dBz强回波伸展高度(4.5~5.5 km)低于0 ℃层(约6 km);此外,西北型的组合反射率(42.9 dBz)和垂直累积液态水含量(5.51 kg·m−2)最高,而西南型最低(40.9 dBz,3.97 kg·m−2)。湖北省短时强降水具有明显的地形效应和局地特征,不同类型短时强降水雨团的持续时间、影响范围、几何形态和物理参数等均有不同。因此,针对不同类型雨团建立差异化的短时强降水预警指标,能有效提升本地短时强降水预警的精细化水平。

     

    Abstract: short-duration heavy precipitation (SHP) is one of the primary meteorological disasters in Hubei Province. Accurately identifying and investigating the classification characteristics of rain cells associated with SHP (SHP-RCs) are of great significance for improving early warning capabilities. Based on the surface automatic stations and national weather radar mosaic data in Hubei Province from 2020 to 2024, this paper utilized the eight-connected chain code algorithm and the spatiotemporal overlapping method to identify and track SHP-RCs. According to their movement characteristics and affect areas, these SHP-RCs were classified into a stationary type and four mobile types (i.e. eastern, southwestern, northwestern, and province-wide types). A comparative analysis was conducted to examine spatial activity patterns and parametric features of different SHP-RC types. The main conclusions were as follows (1) A total of 4 455 SHP cases were identified. The source regions of SHP-RCs were primarily located in the transitional zones between the eastern plain and mountainous areas of Hubei Province, while their active areas were concentrated in central and eastern parts of Hubei. (2) The stationary type exhibited the highest frequency (86%), with the shortest duration (~1.5 h) and the smallest affected area (~568 km2); the province-wide type showed the lowest frequency (1%), with the longest duration (~16 h) and largest affected area (~30 000 km2); the spatiotemporal characteristics of other types fell between these two. (3) The geometric features varied among different SHP-RC types: the stationary type displayed a near-square horizontal shape and a relatively "tall and thin" spatial form, while the province-wide type exhibited an elongated horizontal shape and a relatively "short and wide" spatial form, the geometric characteristics of other types were intermediate; the precipitation top heights of all SHP-RC types exceeded 10 km, with the northwestern type being the highest (11.64 km) and the southwestern type the lowest (10.8 km). (4) SHP-RCs in Hubei Province were predominantly low-centroid heavy precipitation, with the extended heights of 40 dBz strong echo (4.5~5.5 km) lower the 0°C level (~6 km). Additionally, the northwestern type exhibited the highest composite reflectivity (42.9 dBz) and vertically integrated liquid water content (5.51 kg·m−2), while the southwestern type showed the lowest values (40.9 dBz and 3.97 kg·m−2). The above results indicate that SHP in Hubei Province exhibits distinct topographic effects and local characteristics, with differences in duration, affected area, geometric and physical parameters among different SHP-RC types. Therefore, it is necessary to further establish differentiated early warning indicators for different SHP-RC types, which can effectively enhance the precision of local SHP forecasting.

     

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