四川盆地强暴雨过程诊断及中尺度分析

Diagnostic and Mesoscale Analysis on Heavy Rainfall in Sichuan Basin

为了探索四川盆地暴雨天气发生发展的机制,利用云图和美国环境预报中心的全球再分析资料,针对2010年8月18-19日出现的暴雨过程进行环流形势、物理量场及中尺度特征分析,结果表明:暴雨过程中不断有低压槽东移,西太平洋副高西伸至盆地东部,暖湿气流通过低层绕流等方式进入盆地;在低层辐合高层辐散和热力不稳定的条件下,随着干冷空气入侵,对流运动异常强烈,促使强降水发生,湿位涡等值线密集带对暴雨落区预报有较好的指示意义。中尺度对流系统各阶段特征明显,与中尺度气旋演变有很好的相关性。

Based on the NCEP/NCAR reanalysis data and cloud-images, an heavy rainfall occurring in Sichuan Basin during 18 and 19 August, 2010 is analyzed from the circulation, physical quantity field and the characteristics of meso-scale system for finding out the development mechanism of torrential rain. The results showed that： Sichuan Basin was influenced by some low-pressure troughs, and western Pacific subtropical high shifted westward to the east of the Sichuan basin. Under the background of large-scale circulations, warm, moist air continuously entered the Sichuan Basin as a low-level flow around the east of the Tibetan Plateau and so on. Under the condition of lower-level convergence, upper-level divergence, as the dry, cold masses intrusion from the upper troposphere, vertical velocity got much faster, which was probably provided the generation and development of the rainfall. The dense part of MPV has good forecasting significance for the rain loading areas. It was shown obviously that the formation, development, maturity and dissipation of MCS, and its evolution was well corresponding to the meso-scale cyclone,