2017年山东雨季首场暖区暴雨的特征分析

Characteristics of the First Rainstorm Happened in Warm Area in Shandong Province in 2017

利用常规气象观测资料、探空资料、NCEP 1°×1°再分析资料以及卫星资料,对2017年7月6-7日山东雨季首场暖区暴雨的大尺度环流背景、大气层结的垂直结构特征以及触发机制等方面进行分析。结果表明,这次暖区暴雨过程是在副热带高压(简称副高)西北侧的西风带系统与来自低纬度的西南暖湿气流共同作用,并配合低空和超低空西南风急流、切变线和地面热低压的有利背景下产生的;暴雨期间大气均处于真潜在不稳定状态,湿层和暖云层深厚,云底高度低,并伴有较高的降水效率;暴雨过程还经历了垂直风切变由弱变强的转变;对流层下层西南风急流的快速加强和向下传播触发不稳定能量释放,为暴雨的产生提供触发条件,高空西风急流提供强的"抽吸"作用,形成强烈的上升运动;云顶黑体辐射亮温TBB低值区对应强降水的落区,水汽云图和红外云图可以有效地揭示天气系统的发生、发展和消亡过程,以及对流层中上部的动力和水汽特征;暖平流对垂直运动的作用更加明显,低空和超低空急流的预报可以作为日常暖区暴雨的预报着眼点。

Using the conventional meteorological observation data, the sounding data, NCEP 1°×1° reanalysis data and the satellite data, The large-scale circulation background, vertical structural features and triggering mechanism of the first rainstorm rainstorm in Shandong rainy season from 6-7 July 2017 were analyzed. The results showed that:This warm-season rainstorm process is that the westerly belt system on the northwestern side of the subtropical high interacts with the warm-humid southwest flow from low latitudes, and is accompanied by the advantageous background of low-altitude and ultra-low-altitude south-west winds, shear lines and thermal low ground pressure. During the heavy rains, the atmosphere was in a truly unstable state, with deep wet and warm clouds, low cloud heights, and high precipitation efficiency. The torrential rain also experienced a process of vertical wind shear changed from weak to strong. The rapid strengthening and downward propagation of the southwest wind stream in the lower troposphere triggers the release of unstable energy, which provides trigger conditions for the occurrence of heavy rainfall. High-level westerly jet stream provides a strong "suction" effect, forming a strong upward movement. The top of the cloud-blackbody bright temperature (TBB) zone corresponds to heavy precipitation. Water vapor and infrared cloud images can effectively reveal the occurrence, development and demise of the weather system as well as the dynamic and vapor characteristics of the upper troposphere. The effect of warm advection on vertical movement is even more pronounced. The prediction of low-altitude and ultra-low-level jet streams can be used as a forecast point for daily warm-storm events.