一次暴雨过程降水强度“双峰”结构成因分析

Diagnostic analysis on precipitation intensity of the rainstorm with “double peak”

利用LAPS再分析高分辨率资料,对2008年6月9—11日浙、赣、皖地区一次具有"双峰"结构的暴雨过程进行了诊断分析。结果表明:中低层切变线和低空急流是此次暴雨过程的直接影响系统,为暴雨形成提供了良好的动力抬升机制。暴雨过程中暴雨中心区域水汽一直比较充沛且变化较小。对不稳定机制的分析表明,10日03时降水第一峰值可能是由低层对流不稳定和中层条件性对称不稳定机制的共同作用下形成,而条件性对称不稳定可能是10日09时降水出现第二峰值的主要成因,而绝对动量距平调整,则是条件性对称不稳定形成的可能机制。

The diagnostic analysis on the rainstorm with ＂double peak＂ over the Zhejiang-Jiangxi- Anhui region during June 9--11, 2008 is performed by LAPS reanalysis high-resolution data. The results show that the shear line at the middle and low level and southwesterly low-level jet（LLJ） are the domi- nant influencing systems, which provide a significant dynamic lifting mechanism for the rainstorm. The moisture in rainstorm center is enough with small changes. The instability mechanism analysis showed that the first peak of precipitation at 03：00 on June 10 may be caused by the combined actions of low-level convective instability and middle-level conditional symmetric instability（CSI） , in which, CSI may be the main reason for the second peak of rainstorm intensity at 09：00 on June 10. Absolute momentum anomaly adjustment may be a possible mechanism for the formation of the CSI.