Numerical Simulation Of Influence Of Cloud Condensation Nucleus On Hail Weather In Nanjing

This paper uses a mesoscale numerical model(WRF V3.7.1)to conduct a comprehensive analysis and numerical simulation of a hail process that occurred in Nanjing area.Based on actual observation data,cloud condensation nucleus sensitivity experiments on the influence of hail cloud strong convection process was carried out.Then vertical distribution of cloud condensation nuclei was considered.Through the analysis of the macroscopic and microscopic characteristics of the strong convection process and the vertical distribution evolution of the hydrogel particles,the influence on the convective process evolution law and precipitation mechanism was researched.The results show:Under the influence of the northeast cold vortex,due to the title of cold vortex and the trough line with height,the Nanjing area were affected by the dry cold upper air flow from the north and the warm wet lower air flow from the south,which resulting in an unstable air stratification.At the same time,the low-level southwesterly airstream is accompanied by water vapor,which merges with the cold air under the influence of surface cold fronts to form an ascending air convergence zone,triggering the convective process,an continues to evolve under the influence of unstable strata.The hail process took place.Using the NSSL microphysical scheme including prediction of CCN and density of hail and graupel,a strong hail process occurred in Jiangsu province was simulated.The three simulation schemes were designed with the initial concentration of CCN set to the default value of 500m-3 and the observation value of Nanjing value of 4000m-3 ane the test value of 10000m-3.Simulated changes in various hydrogel particles and microphysical structure characteristics were analyzed.The simulation results with the observation CCN value of 4000m-3 are more in line with the actual situation.The low CCN concentration makes the precipitation concentrated in the early stage of the process an there is little hailfall.The high concentration of CCN makes the hailfall area more dispersed and more biased towards the middle an later stages of the process.The difference in initial concentration of CCN has a very different influence on the warm cloud an ice cloud process of this strong convective process:the initial concentration of larger CCN is not conducive to the warm cloud process,inhibits the initial rainwater generation,and hinders the initial development of strong convection process.However,it is conducive to the production of snow and ice ccrystals and release more latent heat,so that the convective intensity of the hail cloud monomer is strengthened,which is more conducive to the generation of ground hail,and the development of hail cloud monomer is more lasting.At the same time,the increase of CCN concentration will reduce the average density of hafnium particles and have little effect on hail density.Considering the evolution of CCN concentration with height,the simulation results are similar to the results of increasing the overall concentration of CCN,which promotes the production of cloud droplets,inhibits the growth of rainwater,reduces surface precipitation and hail,and reduces the atmospheric bottom layer(0?2km).The CCN concentration plays a relatively major role.The number and quality of cloud droplets have increased significantly,which has led to an increase in the number of raindrops but has inhibited the growth of raindrops.Indirectly,the central height of the water content of ice crystals and snow has changed,and the occurrence of hail and hail has been further suppressed.