Comparative analysis on the cause of three heavy rainfall events in Guilin in June 2019

Using the data collected from Doppler weather radar, FY satellite, automatic weather stations and NCEP reanalysis, we have conducted a comparative analysis of the three successive heavy rainfall events occurred in Guilin from June 6 to 12 in 2019 in terms of their circulation background, influence system and cause. The main results are as follow. (1) According to influence system the three events are warm-sector rainstorm, low-vortex rainstorm and frontal rainstorm, respectively, all of which occurred in the superimposed area of the divergence on the right side of upper-level jet and the convergence on the left side of low-level jet. (2) All three events are affected by short-wave troughs at 500 hPa and surface mesoscale convergence lines. In additon, the southwesterly low-level jet and terrain in the first event, the shear line with low vortex in the second event, and the cold front in the third event played an important role, respectively. (3) The trigger systems of the three events are different. The first warm-sector rainstorm event is triggered by windward slope terrain, and the southwest low-level jet maintains the convective clouds which is characterized by backward propagating. The second low-vortex rainstorm event is triggered by the southwest vortex in the low-level in Guizhou area, and in the event the intrusion of western cold air and the reinforcement of southwest low-level jets made the convective cloud with vortex last for a long time. The third frontal rainstorm event is triggered by cold front, which combined with warm and wet airflow in front of the front to strengthen the convective clouds. (4) The patterns of MCS that caused the first warm-sector rainstorm event are mainly the linear backward extension type, and the extremely precipitation occurred in the center and rear part of linear convection echoes. The pattern of MCS that induced the second vortex rainstorm event is the vorticity-stratiform type, and the extremely precipitation occurred near the center of vortex. The pattern of MCS that resulted in the third vortex rainstorm event is the convection system surrounded by stratiform cloud which is changed from linear convection in the rear of stratiform cloud area earlier stage, and the heavy rainfall occurred in the bend of linear convection or the center of strong echo.