云贵高原东段初夏辐合线锋生型暴雨研究

Convergence Line Frontogenesis Type Rainstorm in Early Summer in the Eastern Section of the Yunnan-Guizhou Plateau

利用NCEP 1°×1°再分析资料、探空资料和红外TBB卫星资料对2012年5月11 12日一场典型的初夏暴雨展开分析。结果表明,此次暴雨过程属于贵州典型的辐合线锋生型暴雨类型,地面中尺度辐合线和850 h Pa切变线耦合是对流发展的主要原因,中尺度对流系统在云图上表现为一MCS对流云团自西向东移动。整个暴雨过程中,贵州大部具有高温高湿的层结不稳定特征,低层维持正涡度辐合,高层维持负涡度辐散。锋生函数揭示此类型暴雨天气过程存在明显的锋生现象,水平辐散项F2是引起地面锋生主要的动力因子,而水平辐散项F2和水平变形项F3对850 h Pa锋生有明显的正贡献。用气块理论及其运动学方法来分析对流的触发机制,发现对流的触发与自由对流高度LFC、天气尺度环境场水平辐合的强度、垂直方向辐合高度、辐合持续时间有关。

The convergence line frontogenesis is one of the causes of the rainstorm in the Eastern Section of the Yunnan-Guizhou Plateau,a typical Convergence Line Frontogenesis Type Rainstorm weather was analyzed which was happened from 11 to 12 May 2012,using 1°× 1° reanalysis data of the NCEP/NCAR,sounding data and TBB data of FY-2E.The results show that it is a really typical Convergence Lines Frontogenesis Type Rainstorm in Guizhou,Coupling between mesoscale convergence line and shear line at low-level is the main reason for the development of convection.The mesoscale convective systems triggered due to convection move from west to east as a mesoscale clouds in the Satellite Images.The atmospheric stratification is unstable with hightemperature and high humidity in the process of the typical rainstorm all the time.The strong southwest airflow on 700 h Pa and 850 h Pa provides a better moisture transport condition for heavy rain produced.Positive vorticity and convergence are maintained on low-levels,negative vorticity and convergence divergence are maintained on high-levels.Frontogenesis function reveals the phenomenon of frontogenesis is existed obviously between the ground and 800 h Pa,gradually decreases with height.horizontal divergence term F2 is main power factor causing Frontogenesis on the surface,the horizontal divergence term F2 and horizontal deformation term F3 have a significant positive contribution causing Frontogenesis on 850 h Pa.Using theory of air blocks and method of kinematics to analyze convection,the trigger mechanism of convection is related of LFC,horizontal convergence intensity of synoptic-scale environmental field,convergence vertical height,convergence duration.