A Simulation Study On Characteristics And Evolution Of The Dynamic,Thermodynamic And Microphysics Of A Squall Line Case In South

Using the Weather and Forecasting (WRF) model version 3.1.1 simulated the squall line occurred in the South China on 31 Mar 2014. Based the high-resolution simulated results, the characteristics and evolution of the dynamic, thermodynamic and microphysics of the squall line is analyzed in this paper. It shows that: (1) The squall line formed in the environment with blocking at 500hPa in high latitude, upper jet, lower jet, significantly unstable stratification, and strong low level vertical wind shear. (2) The two convective cells developed with a vertical circulation in the initial stage, which merged and formed the squall line eventually. The strongest convective activities presented in the convective development stage, the pre-squall low,thunderstorm high and wake low began to appear in this stage. The low level (0-3km)vertical wind shear also reached its maximum in the convective development stage,the component of vertical wind shear in the perpendicular direction of the squall line is important to the convective development of the squall line. (3) The new cells were triggered along the cold outflow boundary continuously, causing the squall line propagated in this way. The strong rear-flow in the straitform cut off the front-to-real inflow at middle levels, and cold pool cut off the warm-moist at the surface, leading the decline of the system together. (4) The condensation from water vapor into cloud water, the acceleration from cloud water into rain water and the melting of graupel were the three microphysics processes with larger conversion rate. The evaporation cooling of rainwater contributed to the surface sold pool mostly, and the melting of graupel dominated in the rear inflow. Despite the condensation from water to snow was weak compared with other microphysical processes,it was important to the formation and development of the straitform during the mature stage and dissipation stage. (5) The latent heating effect is more predominant in the convective region. The weak cooling at the upper levels were mainly caused by the sublimation of ice crystal,the evaporation of the super cold cloud water and the condensation from water vapor to ice crystal. The evaporation of the rainwater and cloud water caused the cooling at the surface. However, the strong heating effect in the lower-middle troposphere were the result of multitude microphysical processes, the condensation from the water vapor to cloud water was the largest heating process.