2005年初夏湖南致洪大暴雨中尺度分析

Mesoscale Analysis of Flash Flood in Early Summer of 2005 in Hunan

利用地面加密观测资料、湖南自动站雨量资料、FY-2C卫星TBB资料和多普勒雷达探测等资料,对2005年初夏湖南致洪大暴雨过程进行了中尺度分析。结果表明:大暴雨是中尺度辐合线、中尺度低压和中α尺度对流云团共同作用引发的,高层辐散先于中低层辐合的抽吸机制,θse廓线呈弓形分布的上干冷、下暖湿不稳定层结,南海丰沛的水汽输送是大暴雨形成的物理条件。尺度分离的流场能清晰地分辨中尺度天气系统,中尺度系统对应着雨团活动,积云对流发展早于中尺度系统和雨团的发展;强降水与深对流云团及雷达回波强度强、回波顶高、VIL大的强对流单体有密切的关系。

A mesoscale analysis for the flash flood process in early summer of 2005 in Hunan Province is performed with the surface densified observation, rainfall data of automatic precipitation stations, FY-2C satellite TBB, Doppler-Radar data etc. The results indicate that the heavy rain occurred under the effect of mesoscale convergence line, mesoscale low and meso-α convective cloud clusters together. Suction effect with the divergence in the high level emerging earlier than that of convergence in the mid- and low-level, unstable stratification of the dry and cold air in the high and warm and humid air in the low in accompany with the bow pattern of θse profile and rich water vapor transport from South China Sea are the environmental conditions for the occurrence of heavy rain. Mesoscale systems which are corresponding with the activity of rain clusters can be clearly seen from the stream field after filtering. The development of cumulus and convection is earlier than that of mesoscale systems and rain clusters. Heavy rain is closely connected with the deep convective cloud clusters and convective cells with the strong radar reflectivity, high echo top and big VIL.