沙澧河流域短时强降水特征和概念模型

Characteristic Analysis of the Short-time Strong Rainfall Events and Conceptual Model in Shali River Basin

利用2000-2012年5-9月1 h降水加密观测资料,统计分析了沙澧河流域短时强降水的时空分布特征,结果表明:沙澧河流域短时强降水的空间分布呈自南向北、自东向西减少的趋势;强降水集中出现在6-8月,7月是最为频发月份。日变化呈双峰结构,子夜到凌晨(23时-次日05时)和傍晚前后(18-19时)为易发生时段。应用常规MICAPS地面和高空观测资料对沙澧河流域短时强降水个例天气系统和触发条件进行分析,总结出4种天气学概念模型,分别是有露点锋西南涡型、无露点锋西南涡型、有露点锋切变线型、无露点锋切变线型。其中西南涡型造成的强降水范围比较大,该类型强降水的落区一般位于西南涡移动方向的右前方或其前部切变线与沙澧河流域附近其他中小尺度系统交汇的区域内;切变线型造成的短时强降水范围相对要小,但局地性更强,该类强降水的产生与冷空气的侵入有很大的关系,强降水的落区产生在切变线移动过程中与沙澧河流域附近中尺度系统相交汇或包围的区域内;当有露点锋存在时,短时强降水更偏向于露点锋的两侧,或在露点锋与地面辐合系统相交汇的附近产生。

Based on the 1 h intensive observation data from May to September during 2000-2012, the temporal and spatial distribution features of the short-time strong rainfall in Shali River basin are counted and analyzed. The results show that： the spatial distribution of short-time strong rainfall in Shali River basin trends to reduce from south to north and from east and west; the strong rainfalls occur fre- quently from June to August, and frequently in July. The daily variation shows a double-peak structure, and the rainfall mostly happens from midnight to early morning （23-05） or at dusk （18-19）. Based on the regular MICAPS surface and aerial observation data, the synoptic systems and trigger conditions of the strong rainfall examples in Shali River are analyzed, four synoptic conceptual models are summarized： the southwest China vortex with dew-point front type, the southwest China vortex without dew-point front type, the shear line with dew-point fiont type, the shear line without dew-point front type. The range of strong rainfall caused by southwest China vortex is bigger in general, which is usually located on the right front of the moving direction of southwest China vortex, or on the range where the shear line which is in front of southwest vortex meets with the other medium and small scale systems in Shali River basin; the range of strong rainfall caused by the shear line type is smaller, but local is stronger, the generation of this type strong rainfall is associated with the invasion of cold air. The precipitation range is located on the moving shear line where it meets with the other medium and small scale systems, or besieged by these systems in Shall River basin. When there is a dew-point front, the range of strong rainfall prefers to lo- cate on both sides of the dew-point front, or near the intersection with the ground convergence system.