中文摘要：

利用常规和地面加密气象观测资料、卫星云图、NCEP再分析资料及中尺度模式MM5,对2006年7月23日一次阻塞型华北暴雨过程进行了诊断分析和数值模拟。结果表明,此次暴雨过程发生在以东西伯利亚阻塞高压为典型特征的大尺度鞍型场的背景下,宽广的低压区及高、低空急流次级环流为中尺度对流系统（MCS）的发生、发展提供了适宜的环境和动力强迫;700hPa和850hPa天气尺度的偏西水汽输送和低涡北侧的偏东水汽输送改善了环北京地区的水汽条件,暴雨发生前850hPa中尺度西南水汽输送对北京暴雨的发生有直接影响;MM5模式再现了导致MCS的形成及演变过程;中-β尺度MCS是这次暴雨的直接触发系统,其水平尺度约为0.5个经距,垂直方向由地面伸展到300hPa左右,具有典型的暖心结构,辐合、辐散中心分别位于900hPa和400hPa;MCS北侧强垂直次级环流为强对流的产生创造了有利条件。同时,MCS南侧相当位温的强梯度高能区及该区域的不稳定能量输送也是暴雨发生的重要条件。

英文摘要：

Using the routine and intensive observational data,the NCEP reanalysis data,the satellite images and the high resolution simulation result by MM5,a diagnosis and numerical simulation of a block type convective rainstorm process occurred in North China on July 23,2006 were conducted.The result showed that the process happened in the low pressure circulation,in which the East Siberia Block was the main feature.The broad low pressure area and the vertical secondary circulation induced by the jet stream provided the valuable environmental condition and dynamic forcing for the rainstorm.The water vapor transportation of synoptic scale on 700 hPa and 850 hPa,which was westerly direction to the south of 40°N and easterly direction on the north side of the low,improved the environmental moisture conditions around Beijing.Just before the occurrence of rainstorm,the mesoscale moisture transportation with south-westerly direction on 850 hPa is a key of forming rainstorm.MM5 model successfully reproduced the formation and evolution processes of the mesoscale convective systems（MCS）,which was the directly weather system causing the rainstorm.The horizontally scale of MCS crossed 0.5 longitudes and from surface to 300 hPa vertically with a typical warm heart construction.The strong vertical secondary circulation,which was consistent with strong divergence on 400 hPa and convergence on 900 hPa,produced a favorable condition for the exploding of strong convection.Meanwhile,the instable energy transportation on the south side of the MCS,in which the intensive potential equivalent temperature gradient appeared,contributed to the rainstorm evidently.