干侵入在湖南邵阳一次暴雨中的触发作用

Triggering Effect of Dry Intrusion on a Rainstorm in Shaoyang, Hunan Province

摘要: 利用邵阳地面自动气象站降水观测资料、欧洲中心ERA5再分析资料，对2018年5月6~7日发生在湖南邵阳的暴雨过程进行了诊断分析。结果表明：此次邵阳暴雨过程的发生主要是由于中高层的干冷空气侵入低层造成。水汽的输送主要来源于孟加拉湾的西南气流与南海低压环流左侧的西南气流，强水汽通量辐合区和强降水存在较好的对应关系。高层冷空气南下并向低层渗透形成上层干、下层湿度低的大气结构特征，不稳定的层结条件有利于大气不稳定能量的释放。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，暴雨区与湿位涡负异常值对应关系较好。

Abstract: Using the precipitation observation data from the surface automatic weather station in Shaoyang and the reanalysis data from the European Center ERA5, a diagnostic analysis of the rainstorm process occurred in Shaoyang, Hunan on May 6~7, 2018. The results show that the Shaoyang rainstorm was mainly caused by the intrusion of cold air from the middle and upper levels into the lower levels. The transportation of water vapor mainly comes from the southwest airflow in the Bay of Bengal and the southwest airflow on the left side of the low-pressure circulation in the South China Sea. There is a good correspondence between the strong water vapor flux convergence area and heavy precipitation. The high-level cold air descends south and penetrates into the lower level to form the atmospheric structure characteristics of dry upper layer and low humidity in the lower layer. Unstable stratification conditions are conducive to the release of unstable energy in the atmosphere. The front side of the dry tongue has a good correlationwith the rainstorm area. The rainstorm occurs at the junction of dry air and wet air, and the rainstorm area has a good correspondence with the negative abnormal value of the wet potential vorticity.