基于尺度分离的桂东北一次极端暴雨成因分析

Analysis of the causes of an extreme rainstorm in northeastern Guangxi based on scale decomposition

利用广西降水数据、卫星TBB数据和ERA5再分析资料,基于大气变量物理分解原理,从全球大气分析场中分离出天气尺度扰动场,对2022年6月17—21日桂东北极端暴雨过程进行了多角度分析。结果表明,此次过程发生在充足的水汽供应和有利去稳环境条件下,存在多种不同尺度的上升运动;长时间维持在25°N附近的准静止锋是主要的抬升机制和连续暴雨的主要原因,其南北摆动对应着暴雨带的南北移动,暴雨的强弱变化和锋生扰动一致;造成20日极端短时暴雨的MCC,由锋区内925 hPa和850 hPa气流辐合线所触发和维持;扰动辐合线能很好地指示出降雨中心,暴雨落区位于925 hPa和850 hPa扰动辐合线之间。

Using the precipitation data of Guangxi,satellite TBB data and ERA5 reanalysis data,based on the principle of physical decomposition of atmospheric variables,the synoptic scale disturbance field was separated from the global atmospheric analysis field,and the extreme rainstorm process in northeast Guangxi during 17-21 June 2022 was analyzed from multiple angles.The results show that:This process occurred under the conditions of sufficient water vapor supply and favorable de-stabilizing environment,and there were various ascending motions at different scales.The stationary front which maintained near 25°N for a long time was the main cause of the continuous rainstorm and the main lefting mechanism.Its north-south swing corresponded to the north-south movement of the rainstorm belt,and the variation of the intensity of the rainstorm was consistent with the frontogenesis disturbance.The system responsible for the extreme short-duration rainstorm on June 20,2022 was the MCC,which was triggered and maintained by the convergence line of the 925hPa and 850hPa airflow in the front area.Disturbance convergence lines can indicate the center of rainfall well,the rainstorm falling zone is located between the 925 hPa and 850 hPa disturbance convergence lines.