湖北梅雨期３次大暴雨过程诊断分析

利用常规气象观测资料和NCEP 2.5°×2.5°再分析资料，选取1991年7月9日、1998年7月21日、2010年7月8日湖北省梅雨期的三次大暴雨过程，对影响三次暴雨天气背景以及暴雨发生所需的动力、水汽、热力条件进行诊断分析。试图总结这类区域性暴雨的预报着眼点。结果表明：三次过程的高、低空急流的位置，水汽输送路径有一定相似性；影响三次过程的中尺度系统为西南涡-切变线。850 hPa正涡度中心、水汽通量散度中心与暴雨落区有较好对应，反映了中低层风的辐合和垂直上升运动有利于降水的维持。三次过程暴雨区域700 hPa湿正压项和斜压项绝对值之和均在0.5～0.6 PVU之间，柱状的水汽饱和区均延伸至500 hPa以上；此类暴雨的预报着眼点为：西南涡-切变线以及低空急流的位置是暴雨落区预报的重点，低层的涡度、水汽通量散度、假相当位温高能舌，以及大气运动的垂直结构对暴雨落区预报有较好的参考价值。

Diagnostic analysis of three heavy rainfall processes during Meiyu period in Hubei province

Based on the observed meteorological data and the NCEP reanalysis data（2. 5°× 2. 5°） ,the synoptic background, dynamical conditions, thermodynamic and water vapor conditions of three heavy rainstorms on July 9, 1991, July 21,1998 and July 8,2010 during the Meiyu period in Hubei province were analyzed in order to forecast accurately the similar regional rainstorm. The results show that the locations of upper and lower jet streams and the path of water vapor transport are similar for these three rainstorms. The meso-scale system affecting the three processes is the southwest vortex-shear line. The locations of the positive vorticity center at 850 hPa and water va- por flux convergent center are coincident well with the falling area of rainstorm, which indicates that the low-level wind convergence and vertical ascending motion are favorable to the heavy rain. The sum of the absolute values of moist potential vorticity （MPV）barotropic and baroclinic conditions at 700 hPa in the rainstorm area is about 0. 5 - 0. 6 PVU during the three rainstorm periods, and the humidity saturation zone of the three rainstorms are ex- tended above 500 hPa. The locations of the southwest vortex-shear line and low-level jet stream are important fac- tors for forecasting the falling area of rainstorm. In addition, the low-level vortex, water vapor flux divergence, high energy tongue of the pseudo-equivalent temperature and atmospheric vertical structure could provide references for forecasting the falling area of rainstorm.