【作者】 贾显锋；

【导师】 丁治英；

【作者基本信息】 南京信息工程大学 ， 气象学， 2007， 硕士

【摘要】 本文对1951～2005年发生在柳江流域的致洪暴雨及其影响系统进行了统计分析，发现柳江致洪暴雨和洪涝主要发生于6～7月份；进入20世纪90年代后，柳江致洪暴雨的发生频率和强度都有增加的趋势，洪涝发生的频率和特大洪水发生概率也在增大；柳江东北部流域和西部流域是柳江洪水的主要来源地；柳江水位与降水过程总雨量的关系最密切，过程致洪面雨量临界值为70mm；柳江致洪暴雨的主要影响系统有高空槽、低涡、低层切变线、地面静止锋、低空急流、副热带高压等6种，可分为低槽切变类、低涡切变类和低空急流切变类三种类型。通过对2004年7月19～20日的一次柳江致洪暴雨进行诊断分析，结果表明“两脊一槽”的环流背景，强劲的低空急流和低层切变是本次柳江致洪暴雨过程中、大尺度流场的主要特点；有利的水汽条件、热力条件和动力条件是这次致洪暴雨产生的直接因子；强降水云系在柳江流域附近不断的生成是造成柳江流域致洪暴雨的主要原因；利用MM5数值模式对该过程进行模拟，分析结果得出结论：中尺度涡柱的形成并保持竖直状态是这次致洪暴雨形成的因素之一，涡柱的状态与强降水有关，当涡柱向南倾斜，降水也随之减弱；中β气旋的出现对造成这次强降水过程提供了直接动力作用；CISK机制是这次致洪暴雨的内在机制，它促使深厚对流天气系统形成并维持；高低空急流耦合有利于强对流的发生和发展，是造成这次柳江致洪暴雨的重要因素之一；高层正位涡异常导致高、低空气旋性环流相互作用并增强的正反馈机制也是造成这次致洪暴雨过程的重要机制之一。更多还原

【Abstract】 Statistic is made regarding flood-resulting rainstorm process and it’ssynoptic systems in Liujiang valley from 1951 to 2005. The result show thatflood-resulting rainstorm mainly occur at June or July and the frequency andintensity of flood-resulting rainstorm boost up in this area after 90s of the20th,the result also show that Liujinag flood is mainly come from east-northarea and west area of Liujiang valley. The correlation between Liujiang riverlevel and total process precipitation is most important, 70mm total arearainfall can cause Liujiang flood. The study also find that synoptic systemscausing flash-flood-producing rainstorm are upper-air trough,lowvortex,low-level shear,surface static front,low-level jet,Subtropical Highect,they can be devided as low trough-shear,low vortex-shear and low leveljet-shear three types.We made physical diagnosis about a flood-resulting rainstorm process inLiujiang area on 19-20 July 2004 and found that "2 ridge 1 trough"circulation background,strong low-level jet and low-level shear are thecharacteristic of meso-scale and lagre-scale circulation during thisprocess. The advantaged condition of moisture,heat and dynamic are directfactor which cause this process. Cumulonimbus generate frequently in thisarea,this bring flood-resulting rainstorm. We made numerical simulation teston this process by using MM5 model,by analyse the model ouput we findthat meso-scale vortex pole is builded and maintained is one of factors offlood-resulting rainstorm,heavy rain has relationship with vortex polestate,when vortex pole incline towards south,rainfall weaken. B meso-scalecyclone offer direct dynamic power for this process. We also found thatmechanism of CISK is the internal factor of this process,it forces deepconvection and maintain. The coupling of upper and lower tropospheric jetstreams is advantaged for causing strong convection, this is also one of factorsof flood-resulting rainstorm in Linjiang area.Abnormity of positivePV(potential vortex) in upper air result in interaction of cyclonic circulationin upper air and low air,this positive feekback mechanisim is also one ofimportant mechanisim which lead to this flood-resulting rainstorm process.更多还原