四川盆地一次暴雨过程的初步分析

Analysis of a Heavy Rain Process in Sichuan Basin

利用NCEP 1°×1°再分析资料、结合多种数值预报产品对2007年7月27—29日发生在四川盆地的大范围暴雨过程进行了分析。结果表明:这次暴雨环流不同于四川盆地常见的四种基本类型,主要表现为500 hPa中高纬度为两槽一脊并在贝加尔湖南侧伴有大范围阻塞高压,西太平洋副热带高压588线西端位于114°E附近,同时河套附近的冷涡为此次降水的发生补充了冷空气,大气低层伴有西南低涡,云南、贵州、四川一带维持一支8～12 m/s的西南急流;高层辐散、低层辐合的垂直配置及暴雨区维持的垂直环流是此次暴雨发生的动力条件;暴雨区的降水中心变化,与垂直环流的上升区域位置变化有密切关系;欧洲数值预报产品对此次暴雨发生的环流形势预报效果较好,具有很好的预报参考价值,但数值预报产品对降水量级的预报误差较大。

By using NCEP 1°×1° re-analysis data and numerical forecast products to analyze a heavy rainstorm process in Sichuan basin from 27th to 29th July 2007, the results showed that the circulations of this heavy rainstorm was typical and different from four basic rainstorm types. It displayed circulations of two-through and a-ridge with large blocking high in Baikal lake region at 500 hPa in Asia middle-high latitude regions, meanwhile, the edge of subtropical always exited 114°E nearly and cold vortex kept in Hetao regions during rainstorm. There were southwest vortex and low level jet stream which existed in Yunnan province, southern plateau of Sichuan and Guizhou province at 850 hPa. The vertical allocation of the divergence at upper and convergence at low level and the sustaining vertical circulations in rainstorm region were the important meehanismes for the successive heavy rain storm. The changes of rain center had relations with position of ascending air current of vertical circulations. The ECWMF products had a good performance on circulations forecast of this case except the rainfall rating error of numerical forecast of T213 model, Germmany model and Japan model.