华南前汛期福建一次致洪暴雨过程的中尺度结构特征

利用FY-2E卫星云顶亮温资料、全国加密自动站资料和NCEP再分析资料,对2010年6月19～20日华南前汛期福建一次特大暴雨过程的中尺度对流系统的演变及其结构特征进行了分析和讨论。结果表明,特大暴雨发生在稳定的环流背景下,整个过程有4个主要的中尺度对流系统,沿着低层切变线东移和发生、发展,为强降水的发生提供了有利条件;高层辐散和低层辐合促进了强降水区中的上升运动,低层辐合的水汽在强上升过程中释放凝结潜热,进一步促进了水汽的上升运动和低涡的发展,是强降水发生的动力特征;地面不稳定能量和西南暖湿气流在强上升运动作用下,与中高层沿等θse线向低层侵入的干冷空气在对流层中层相遇并形成锋区,是特大暴雨过程的热力特征;湿位涡的诊断分析表明,对流不稳定和条件性对称不稳定的发展促使强降水区附近的涡旋发展,上升运动的加强,对强降水的发生和持续起了重要作用。

Mesoscale Structure Characteristic of Heavy Flooding Rainstorm Process in Fujian in Preflood Period of South China

The infrared brightness temperature of FY-2E at cloud top data,regular observation data,AWS data and NCEP reanalysis data were used to analyze and discuss the evolution and structure characters of the mesoscale convective systems(MCS) of the heavy rainstorm that happened from 19 to 20 June,2010 in preflood period of South China.The obtained result are as follows.Firstly,there were mainly four MCSs developing and moving eastwardly along shear line on 850 hPa,which provided favorable conditions for the severe precipitation.Secondly,the divergence in upper level and the convergence in lower level promoted the upward movement of the rainy area,furthermore,the condensation latent heat is released by the water vapor of convergence in lower level being in the ascending process which accelerate ascending of water vapor and developping of the low vortex.Those are the dynamical characters of the severe precipitation.Thirdly,the unstable energy at the surface and southwest warm and wet stream moved upwardly by strongly upward motion and cold air from middle and high level toward lower level along isoline of θse encountered in the middle level to form the frontogenesis area,which is the thermodynamic character of the extreme rainstorm.Fourthly,the diagnostic of the Moist Potential Vorticity(MPV) indicated that the development of convective instability and conditional symmetry instability,which induced the vortex developing and aggravating ascending movement near the severe precipitation area,played an important role in the genesis and maintaining of the severe precipitation.