湘北地区2014年7月12-18日暴雨天气过程技术总结

The Analysis of 12- 18 July 2014 Rainstorm in North Hunan Province

2014年7月12~18日澧水流域、沅水流域上游及湘北连续出现强降水,由于降水持续时间长,强降水时段集中,导致严重的暴雨洪涝灾害。针对这次天气过程,通过对探空资料、地面自动气象站观测资料、FNL再分析资料和FY-2E卫星资料等分析,结果表明,夏季东亚大槽的建立与维持,西南低涡东移和副热带高压外围西南暖湿气流的相互配置引发了这次强降水;TBB低值带与强降水区域有很好的对应关系;西南涡东移路径上地面潜热通量的加入促进西南涡发展,增强降水;强降水过程中湘北地区K指数维持28℃,假相当位温维持76℃,以上阈值可作为湘北强降水发生的阈值;低空螺旋度维持30×10-8h Pa/s2,高空螺旋度维持-30×10-8h Pa/s2,可作为湘北地区强降水动力条件阈值;低层大气受涡度平流和辐散影响为正值层,高层大气受平流项影响为负值层,有利于大气动力对流加强;分析视热源发现,低层暖源、高层冷源有利于热对流活动。

The Li water basin,Yuan water basin and their upstream had been attacked by rainstorm during 12- 18 July 2014. Because of a longtime and strong precipitation,severe floods happened. Aiming at the process,we make use of the detection data,the ground automatic weather station data,the FNL data,the FY-2E satellite data to analysis the cause. The results of the study shows that the establishment and maintenance of east Asian large tanks in summer along with the warm moist air and the southwest vortex eastward trigger the heavy rain; TBB low band has a good correspondence with the heavy rainfall area; The southwest vortex will develop to enhance precipitation,when the latent heat flux join; In Changde City,the K index maintained 28℃ and the pseudo-equivalent temperature maintained 76℃ during rainstorm. So,these two indicators can be used as heavy rainfall threshold. The helicity of lower maintained 30 × 10- 8h Pa / s2,at the same time,the helicity of upper maintained- 30 × 10- 8h Pa / s2. These two indicators can be used as dynamic threshold in Changde City; The lower atmosphere is influenced by the advection and divergence of vorticity as a positive layer,the upper influenced by the vorticity advection as a negative layer,it is conducive to the dynamic convection; Through research on vertical distribution of apparent heat source,it is founded that the lower works as the cold source,the middle works as weak warming source,the high-level works as strong cold source,the vertical distribution above is conducive to the heat convection.