【作者】 雷蕾；

【导师】 朱伟军； 周毓荃； 毕宝贵；

【作者基本信息】 南京信息工程大学 ， 气象学， 2007， 硕士

【摘要】 本文采用各种常规天气资料、NCEP／NCAR再分析资料和FY-2C卫星、TRMM卫星及多普勒天气雷达等遥感资料，结合MM5中尺度数值模式模拟研究了2005年6月25-26日一次低涡过程在我国中东部形成的混合云系和降水的宏微观结构特征以及形成机制。通过对常规以及遥感资料分析发现：低涡东移北抬过程中，由于混合云系不同部位存在不同的动力、热力以及水汽条件，云系结构十分不均匀，黄淮流域出现八个中尺度对流云团，冷云盖亮温可达-90℃以下，对流十分旺盛。受其长达十几小时的生消演变活动影响，河南25日14时至26日07时出现大范围降水，局地出现强降水。分析TRMM卫星对于6月25-26日的混合云系和降水的观测发现：层云降水率远远小于对流降水率，后者是前者的四倍；对流降水的雨谱明显比层云雨谱宽，层云降水中＜10mm的降水是主要的，而对流降水中10～20mm的降水占了主要地位。层云降水廓线与对流降水廓线也存在明显的区别，粒子增涨的范围和高度差别较大，对流降水中播撒—供应机制显著，并且暖雨碰并过程也比层云充分的多。进一步利用MM5v3.7中尺度数值模式对这次天气过程的天气形势、云场特征、降水分布、雷达回波等特征进行模拟研究，并且分析该低涡混合云系产生降水的湿热力、动力结构，不稳定度，云内的微观结构特征以及形成降水的微物理过程。结果表明：模拟的天气形势、云系、降水等特征与实况比较接近。低涡混合云系降水较强的区域不稳定指数大，可以达到产生暴雨的级别，降水区外围不稳定指数小；较强降水区低层很湿，动力场的辐合把水汽向上输送促使了云系的对流发展，这是空中云水向降水转化非常重要的条件。降水过程中云内的微物理结构也发生了很大的变化，整个过程云水含量比较丰富，但冰晶含量相对较少，初始时雪、霰含量非常少，25日14时之后迅速增加，因此初始时刻降水主要表现为暖雨特征，随后由于云体发展，出现大量雪、霰粒子，降水则表现为冷云降水为主，暖雨过程为辅，两者共同作用特征。通过各种资料以及模式的结合分析与研究，本文对低涡天气系统下形成的混合云系和降水分布形势、结构的不均匀性、微物理特征以及产生的物理机理等有了比较全面的认识。降水云系的各种尺度结构特征明显，不同尺度之间存在相互作用和反馈，降水的形成往往是由于大尺度背景场、中尺度环境以及云内微物理过程共同作用的结果。因此，全面研究云和降水的宏微观结构特征对于天气预报中降水的精确预报以及人工影响天气合适作业部位的选择都有重要意义。更多还原

【Abstract】 This paper analyses some characteristics of the macro- andmicro-physical structures and mechanism of a case of mixed cloud aswell as precipitation in a low vortex synoptic process on June 25 to 26,in 2005, by using different observational data, NCEP/NCAR reanalysisdata, remote sensing data such as FY-2C satellite data, TRMM satellitedata as well as Doppler Radar data, and the middle scale numericalsimulation models MM5.Some conclusions were drawn. In the process of the low vortexmoving, because of there being different dynamical, thermal and vaporconditions in the different area of the mixed cloud, eight intensemiddle-scale convective clusters appeared in the Huanghuai River areaand the Black Body Temperature was below 90℃. Because of theseconvective clusters effect for about more than ten hours, large areas inHenan province had precipitation and some palaces had strong rainfallsfrom 14 on June 25 to 7 on June 26. The TRMM satellite data showed usthat the stratiform precipitation rate was far below the convectiveprecipitation rate, and the latter was four times than the former. Theconvective precipitation spectrum which mainly from 10mm to 20mmwas wider than the stratiform which was mainly below 10mm. Besides,there was obvious difference between the stratiform cloud profile and theconvective cloud profile, mainly existing in the range and the height ofthe particle rose. Obviously the seeding-feeding mechanism and thewater drop collection process were great important in the convectiveprecipitation. The MM5v3.7 version numerical simulation model, which wasdesigned three levels nestdown and properly physics parameterizationoptions, was used in this paper to supplement above analyses. Thesimulated characteristic of the synoptic background, the cloud figure andthe precipitation were close to the fact. So based on these conclusions,the instability index, the thermal dynamics conditions, and themicro-physical characteristic (such as ice, snow, graupel, cloud water,and rainwater content) were calculated. Some conclusions were drawnbelow. The instability index in the strong rainfall area was much largerthan that in the periphery area. There was an important condition forcloud water convert to precipitation that the low atmospheric level hadso many vapors and the convergence transferred the vapor to the upperair made the convective cloud development. In the precipitation process,the cloud micro-physical structure changed obviously, which had muchcloud water all the time, but had little ice content. The snow and thegraupel content were so small in the beginning, but increased swiftlyafter 14 on June 25. So at the beginning, the warm rain process was inthe main status and latter the cold rain process was stronger than that.Above all, the cloud and precipitation distribution, theinhomogeneous structure, the micro-physical characteristic and the formmechanism in the low vortex synoptic process were analyzed anddiscussed carefully. Different scale characteristics were obviously in themixed cloud and precipitation, and they had closely interactions witheach other. The form of the precipitation always was the results oftogether actions of the large scale synoptic backgrounds, the middle scale conditions and micro-physical process in the cloud. So on thispoint of view, it is of great importance to completely study the cloud andprecipitation macro- and micro-physical structure characteristics in orderto forecast rainfall precisely and to choose the proper area in weathermodification.更多还原