湘西北一次大暴雨过程中尺度结构特征分析  

ANALYSIS OF MESOSCALE FEATURES ASSOCIATED WITH A HEAVY RAINSTORM IN NORTHWESTERN HU′NAN PROVINCE

作　　者：陈红专[1] 叶成志 杨云芸 王晓雷 

机构地区：[1]怀化市气象局,湖南怀化418000 [2]湖南省气象台,湖南长沙410007

出　　处：《热带气象学报》2015年第6期839-851,共13页Journal of Tropical Meteorology

基　　金：财政部/科技部公益类行业(气象)科研专项(GYHY201306016);中国气象局气象关键技术集成与应用项目(CMAGJ2015M40);中国气象局预报员专项(CMAYBY2014-045)共同资助;湖南省气象局重点项目(XQKJ15A002)

摘　　要：利用常规观测资料、区域自动气象站资料、多普勒雷达资料、美国GFS及LAPS分析资料,对2012年6月下旬发生在湘西北的大暴雨过程的成因以及β中尺度系统的三维动力热力结构特征进行了分析,结果表明:此次过程属于典型的湖南盛夏低涡切变型暴雨过程,地面降水在时空分布上具有明显的中尺度特征。低空急流加强北推不但有利于水汽和不稳定能量向暴雨区的输送,也是β中尺度低涡发生发展和垂直上升运动加强的主要原因。地面中尺度辐合线的维持和地形的阻挡有利于暖湿气流的抬升,而上升的暖湿空气在中高层凝结释放潜热,对上升运动起到正反馈作用。产生暴雨的β中尺度系统具有明显的动力、热力结构特征。在暴雨发展的最强阶段,β中尺度系统的四周各有一个垂直环流圈,其中南北两侧的下沉补偿气流向暴雨区的分支不但有利于水汽和不稳定能量的输送,也加强了暴雨区低层的辐合;东西两侧下沉补偿气流向暴雨区的分支加强了暴雨区气流的气旋性弯曲,更进一步加强了β中尺度系统的辐合;基于上述研究成果,提炼了此次低涡切变线暴雨的三维物理结构示意图。The causes and three-dimensional mesoscale features of a heavy rainstorm that occurred in June 2012 in the northwestern Hunan province are analyzed using various conventional and non-conventional meteorological data. It is shown that this rainfall event is a typical rainstorm driven by a vortex and a shear. In the whole process, the surface rainfall showed obvious mesoscale features. The strengthening and moving northward of a low-level jet not only contributed to the transport of water vapor and instability energy, but also played an important role in the development of a meso-β vortex and the strengthening of vertical ascending motion. The presence of a surface mesoscale convergence line and terrain blocking also contributed to the uplifting of warm and moist airflow, which resulted in condensation and release of latent heat and therefore establishment of positive feedback to the ascending motion. The meso-β system has some remarkable dynamic and thermal structures. During the strongest stage of the rainstorm, significant vertical circulation cells can be identified around the meso-β system. The compensating subsidence from the southern cell acted to enhance the low-level southwesterly warm and moist airflow. Besides, its northern counterpart acted to strengthen low-level convergence in the heavy rain area. The compensating subsidence from both the eastern and western cells was beneficial to the cyclonic curvature of airflow, which further strengthened the low-level convergence. A conceptual model is proposed to illustrate the roles and typical three-dimensional structures of the meso-β vortex associated with this vortex/shear heavy rainstorm in Hunan province.

关 键 词：天气学 大暴雨 中尺度结构特征分析 低涡切变型 中尺度垂直环流 

分 类 号：P426.62[天文地球—大气科学及气象学]