干侵入在云南一次全省性暴雨中的触发作用

利用常规观测资料和NCEP再分析资料,对2013年8月2425日发生在云南的强降水事件进行诊断分析.结果表明热带低压西行过程中来自中高层的干冷空气侵入造成了大范围强降水的发生.稳定而持续的水汽输送和水汽辐合是暴雨形成的重要因素,高层冷空气南下并向低层渗透造成的对流抬升又使得对流加强,利于暴雨的产生.冷空气与偏东急流长时间交汇于滇东北,造成滇东北暴雨维持时段较长;而滇西南干舌与热带低压交汇时段和区域正好对应着暴雨时段.干舌前侧与暴雨落区有较好相关性,暴雨发生在干空气与湿空气交界处,暴雨区与MPV异常值对应关系较好.

On the triggering mechanism of the dry intrusion on a rainfall process in Yunnan

By using routine observation and NCEP reanalysis data,the characteristic of the heavy precipitation events in Yunnan in August 2425,2013 has been analyzed.The results show that the large scale heavy rainfall can be caused by the movement of the westward typhoon and the invasion of the dry and cold air in middle troposphere.Stable and sustained vapor transportation and vapor convergence are important factors to heavy rainfall.Convective uplift which is caused by dry and cold air moving forward south and penetrating to lower level will enhance the convection,which would help the occurrence of rainstorm.On the one hand,two conditions that cold air meets on east side jet in northeast Yunnan for long time can cause long time heavy rainfall in northeast Yunnan.On the other hand,the intersection time and region of tongue dry air and tropical depression just correspond to the time and region of rainstorm in southwest of Yunnan.The front of dry cold air is a good correlation of rainstorm region.heavy rain occurring at the region where the back part of dry air joined with humid air mass.The area of heavy rain has better corresponding relation with the region where MPV is unusual.