中文摘要：

利用NCEP/NCAR再分析资料对2008年7月17～21日发生在山东地区的强降水事件进行了分析,发现这次强降水是在中低纬度系统相互作用下产生的。对干侵入特征的分析表明,这次强降水事件中干空气主要以纬向侵入为主,这与济南＂7.18＂暴雨不同。通过对假相当位温（θse）的诊断分析发现,干空气侵入一方面有利于锋区的形成和维持,另外一方面还能够加剧低层的对流不稳定度,有利于对流运动的维持和发展。湿位涡场的分析则表明,高位涡的下传是干空气侵入的一种可能机制,干侵入是高位涡下传的一种表现方式。

英文摘要：

By employing the NCEP/NCAR reanalysis datasets,the characteristic of the torrential rain event occurred in Shandong Province is analyzed.The results show that the interaction between mid and low latitude systems play an important role in the occurrence of the torrential rain event.The feature of dry air intrusion is also analyzed,it＇s different from the ＂7.18＂ torrential rain occurred in Jinan and mainly presents a zonal intrusion characteristic.Through the diagnostic analysis of pseudo-equivalent potential temperature（θse）,it is found that the dry air intrusion is advantageous to the formation and maintenance of frontal zone,in addition,the dry air intrusion can cause the increase of convective instability which is useful to the maintenance and development of convection.The analysis of MPV（Moist Potential Vorticity）shows that the probably mechanism of the dry intrusion is that the high potential vorticity descends from the upper troposphere to the lower level,therefore,the dry air intrusion is one kind of the high MPV forcing.