Numerical Simulation And Self Organization Process Study Of A Strong Squall Line In South China

WRF model was used to investigate the diagnostic role of rear inflow in a squall line occurred on 30-31 March,2014 in South China through numerical simulation.The upper trough and the low vortex were the main influencing systems of the squall line,sufficient water vapor,low-level vertical shear were significant meanwhile.Results show:at the development stage,the squall line system origined in two convective cells,later Rear Inflow Notch began to appear,and the squall line gradually evolved into a bow echo.In front of the squall line,new convection system appeared.Within combining the two,the merger of the cells between these two convective systems was mainly due to convergent uplifting caused by the downdraft between them.During the mature stage,the merger of the cells in the convective system is similar to the relationship between chasing and supply.Rear Inflow Jets(RIJ)gradually descended to the ground and extended to the leading edge of the convection region.When the cold pool of the squall line completely moved into the front residual cold zone,with Jiulian Mountain downhill and cold pool strengthened process,the squall line developed.The movement of squall line is nearly consistent with the direction of the 1000-500hPa layer thickness and low-level vertical wind shear ahead.Meanwhile,the motion of the squall line can be estimated by the proposal of Corfidi.Rear Inflow Jets played an important role of development and maintenance of the squall line.RIJ was first disturbed by the environmental flow and the middle pressure deficit,and then bookend vortices in the back edge of the convection zone enhanced it.The cyclonic vortex was mainly affected by the stretching term,while the anticyclonic vortex was mainly affected by the tilting term.The vortex pairs were mainly caused by the upward tilt of the low level horizontal vorticity which came from the baroclinic term.