“987”突发大暴雨及中尺度低涡结构的分析和数值模拟  

Analyses and Numerical Simulation on an Abrupt Heavy Rainfall and Structure of a Mesoscale Vortex during July 1998

作　　者：程麟生[1] 冯伍虎[1] 

机构地区：[1]兰州大学大气科学系,兰州730000

出　　处：《大气科学》2001年第4期465-478,共14页Chinese Journal of Atmospheric Sciences

基　　金：国家重点基础研究发展规划项目G1998040907

摘　　要：１９９８年７月２０～２３日（简称“９８７”），发生在鄂东和鄂西南地区的突发性特大暴雨过程在长江流域是罕见的。该过程与 ５００ ｈＰａ短波槽和 ７００ ｈＰａ低涡切变线以及沿切变线相继生成和强烈发展的β中尺度对流系统密切相关。对该过程采用非静力ＭＭ５的二重网格双向嵌套进行了全物理过程的数值模拟，其中，可分辨尺度降水采用Ｒｅｉｓｎｅｒ混合相微物理显式方案，次网格尺度降水采用Ｇｒｅｌｌ积云参数化方案。双向嵌套的细网格模拟结果揭示，武汉周边地区的特大暴雨与 ７００ ｈＰａ上一个β中尺度低涡的生成和强烈发展直接关联。该低涡具有明显的动力－热力结构特征：特强上升运动与饱和气柱互耦，超强散度柱与强涡柱耦合发展，湿静力不稳定与湿对称不稳定共存，深对流湿气柱内云团发展的微物理场结构比较典型。细网格域内前 ３６ ｈ的降水分布和雨强与观测的大体相应，扩展域细网格的降水模拟明显改进了原细网格的模拟，特别是雨带。这一结果还表明，对持续时间较长的大暴雨，大尺度过程对中尺度系统的影响是重要的。During 20-23 July 1998, an abrupt extraordinarily heavy rainfall event occurred in the eastern and southwestern parts of Hubei Province, which is seldom in the Changjiang River basin. Analyses indicate this event was in close relationship with the short wave trough at 500 hPa and low vortex with shear line at 700 hPa as well as with successive generating and intensive developing of MβCS along the shear line. This event was simulated by numerical simulation of full physics using nonhydrostatic version MMS (V2.12) with two-way interactive and double nested grid, in which Reisner's mixed-phase explicit scheme was used to resolvable scale precipitation microphysics, and Grell's cumulus parameterization scheme was adopted by subgrid scale precipitation physics. The simulated results using two-way interactive fine grid reveal that. the extraordinarily heavy rainfall in the Wuhan periphery was in direct relationship with the genesis and intensive development of a meso-β scale low vortex at 700 hPa; this low vortex had obvious dynamic-thermodynamic structural feature: the extremely intensive ascendant motion was intercoupled with saturated air column; the surpassing intensive divergence column and intensive vorticity column were coupling developed, the moist static instability and the moist symmetric instability was coexist; the structure of the microphysic fields of the cluster developing in the deep convective moist air column is typical. The rainfall distribution and intensity before 36 h in the fine domain were roughly correspondent with observations, the simulated precipitation as mentioned above is obviously improved by the simulation of the extended fine domain, especially rainfall belt. The result also shows that the influence of the large scale process on the mesoscale systems is important to the persistently heavy rainfall.

关 键 词：特大暴雨 低涡切变线 β中尺度低涡结构 非静力模式 数值模拟 1998年 

分 类 号：P458.121.1[天文地球—大气科学及气象学] P435