In this paper,a southwest vortex rainfall process of 8—9 July 2010 over Sichuan Basin is simulated using the Mesoscale Weather Research and Forecasting (WRF) model.The simulation results are then utilized to estimate the entrainment rate in convective clouds under 0 ℃ layer.It is found that the vertical distribution characteristics of simulated precipitation particles are roughly consistent with the observed characteristics,proving that the WRF accurately simulates the vertical distribution of precipitation particles in the southwest vortex precipitation cloud system.The simulation results show that the liquid water content,vertical velocity and buoyancy in the clouds increase with height above the cloud base and decrease with height close to the cloud top.However,the moisture static energy (MSE) mainly reduces with cloud height.In the case of entrained air far away from the cloud edges,the entrainment rate decreases with height above the cloud base and increases with height towards the cloud top,while the intensity of the entrainment rate towards the cloud top weakens,and the mean entrainment rate decreases.In addition,the entrainment rate is negatively correlated with both cloud water content and rain water content in cloud,indicating that the entrainment increases the evaporation of cloud droplets,reduces the size of droplets and consequently suppress the development of convective clouds and precipitation.When we assume that the entrained environmental air surrounds the cloud edge,the estimated entrainment rate is higher than the corresponding value when we assume that the entrained air is far away from the cloud edge.However,the vertical distribution characteristics of entrainment rate and the influence of entrained air on the clouds are similar under the two assumptions.Both assumptions have advantages and disadvantages that should be considered when determining the entrapment rate of the southwest vortex cloud system.Moreover,the entrainment rate decreases over time,which is related to the development and growth of the cloud ensemble during this time.The results in this paper provide a theoretical basis for further research on entrainment rate parameterization in the Sichuan basin.