2019年3月岳阳一次强对流天气过程的成因分析

Cause Analysis of a Severe Convective Weather Process in Yueyang in March 2019

整理分析岳阳2019年3月20—21日常规天气观测资料、NECP再分析数据,结合多普勒天气雷达资料及产品,应用天气学、雷达气象学方法对此次强对流天气过程的背景及环境场条件进行分析。结果表明,前期不稳定能量积聚,19—20日地面倒槽发展,南风强盛,岳阳市前期地面升温明显,最高气温达到28℃以上;500 hPa中高纬为多波动型,湖南处于槽前西南气流控制下,850 hPa四川、贵州交界处有低涡形成,中低层切变移动影响岳阳,为此次强对流过程提供了动力条件;地面冷空气南下,斜压锋生,触发对流发展;中低空西南急流建立,来自孟加拉湾的强盛的水汽输送与持续的水汽辐合,为此次强对流过程提供了充沛的水汽供应和动量输送,同时也大大加强了低层上升运动的形成,为降水的发生发展提供了动力与热力条件;此外,垂直上升运动的大值区与强对流发生时段对应较好,K指数、沙氏指数及对流不稳定能量CAPE已达到岳阳出现强对流和短时暴雨指标;在强对流预报中,不仅要考虑大尺度环流及特征物理量,也要考虑地形对降水及强对流天气的影响。

Based on the routine weather observation data and NECP reanalysis data from March 20 to 21,2019,combined with Doppler weather radar data and products,the background and environmental field conditions of this severe convective weather process were analyzed by using the methods of synoptic and radar meteorology.The results showed that the unstable energy accumulated in the early stage,the ground inverted trough developed from March 19 to 20 and the south wind was strong.The ground temperature increased significantly in the early stage of Yueyang City,and the maximum temperature reached above 28℃.500 hPa middle and high latitudes were multi-wave type,and Hunan Province was under the control of southwest airflow in front of the trough.There were low vortices at the junction of Sichuan and Guizhou at 850 hPa,and the shear movement of the middle and lower layers affected Yueyang,which provided a dynamic condition for the strong convective process.The cold air on the ground moved southward,baroclinic frontogenesis triggered the development of convection.The southwest jet of middle and low level was established.The strong water vapor transport and continuous water vapor convergence from the bay of Bengal provided abundant water vapor supply and momentum transport for the strong convection process,as well as the formation of the ascending movement in the low level,which provided the dynamic and thermal conditions for the occurrence and development of precipitation.In addition,the large value area of vertical ascending motion corresponded well with the period of strong convection,and the K index,Showalter index and convective instability energy CAPE had reached the index of strong convection and short-term rainstorm in Yueyang.In the prediction of severe convection,not only large-scale circulation and characteristic physical quantities,but also the influence of topography on precipitation and severe convective weather should be considered.