济南“7.18”大暴雨中尺度分析

Mesoscale Analysis on a Heavy Rainstorm in Jinan on 18 July 2007

综合利用常规资料、加密自动站观测资料、NCEP再分析资料、CloudSat卫星及多普勒天气雷达资料,分析了2007年7月18日济南市百年一遇的突发性大暴雨天气过程的成因及中尺度特征。结果表明,这次对流性大暴雨是由高空冷涡南部低槽、低层准东西向切变线、西太平洋副热带高压西北边缘的暖湿气流以及自东北南下冷空气共同影响所致;根据单雷达反演风场及加密自动站观测可知,边界层中尺度辐合中心和辐合线的生成、发展是这次大暴雨产生的启动机制,大暴雨的分布与地面辐合线的走向基本一致,并随其移动而移动;边界层辐合线相交处有中尺度辐合中心发展,造成水平风场的强辐合,从而增强了该地区水汽和能量的积聚;两部雷达回波显示,在两个东西向的带状回波衔接处,对流增强,降水亦增强。垂直结构分析表明,暴雨强盛期低层辐合与中高层辐散几乎垂直,显示中尺度对流系统具有较强的斜压性特征,垂直倾斜的上升气流以及两侧明显的下沉补偿气流表明,该中尺度对流系统具有对流型风暴结构特征。

A mesoscale heavy rainstorm in Jinan on 18 July 2007 is analyzed using the special observational data,including Doppler radar products,automatic meteorological station data,NCEP/NCAR reanalysis data and CloudSat satellite data.It is found that the heavy rainstorm process is generated by the interaction of westly trough,the southwest warm and wet airflow on the edge of West Pacific Subtropical High and the cold air from the north.The result shows that the mesoscale convergence center and line play important roles,which is the start mechanism for the heavy rainstorm.Furthermore,the heavy rainstorm occurres near the center of mesoscale low pressure and accompanies with them.The mesoscale convergence center develops at intersection of the boundary layer convergence line,which increase the strong wind convergence and accumulation about moisture and energy.Radar products show that convection and precipitation enhance at the junction between two strong east-west echo bands.In the vertical direction,low level convergence and high level divergence are almost vertical.This configuration shows that mesoscale convective system has strong baroclinic characteristic.This case has the typical characteristic of convective storm,accompanying with vertical tilt of updraft and obvious sink flow compensation on both sides.