A Study On The Physical Process Of Summer Convective Cloud Precipitation In The Nagqu Region Of The Qinghai-Tibet Plateau

In this paper,the temporal and spatial distribution of convective activity is analyzed by using the observation data and satellite data of the third Qinghai-Tibet plateau atmospheric science experiment in Nagqu area of the Qinghai-Tibet Plateau in summer of 2014.In addition,the mesoscale model WRF was used for the control experiment of the parameterization scheme,and the applicability of the cloud microphysical parameterization scheme was analyzed in the plateau.The optimal parameterization scheme was used to simulate a typical flow cloud precipitation process,and the microscopic physical characteristics of the flow cloud precipitation in Nagqu area of the Qinghai-Tibet plateau were analyzed in summer.The sensitivity experiment of relative dispersion of cloud drop spectrum is conducted,so as to improve the simulation ability of the model on the plateau.The main conclusions of this paper are as follows:(1)Using the black body brightness temperature data from the FY-2E satellite data,it can be concluded that the TBB values in the central and southern plateaus are lower and lower than those in the middle and lower reaches of the Yangtze River at the same latitude,indicating that the cloud tops in the central plateau are higher;The daily precipitation data can find that the precipitation in Nagqu area has a quasiperiodic change in June and a quasi-two-week cycle change in July-August.(2)By analyzing the FY-2E infrared cloud image and Ka-band millimeter wave cloud radar data,we can get the time of the occurrence of convective cloud precipitation and the temporal evolution of convection activity over time.The summer convection activity in Nagqu area is strong,and the June precipitation in Nagqu area is quasi-periodic July-August precipitation showed a quasi-two-cycle distribution;(3)Using the mesoscale model WRF to simulate a typical convective cloud precipitation from August 7th to 8th,2014,and using the sensitivity experiments of four cloud microphysical parameterization schemes,it was found that the Lin scheme is more suitable for simulation in time and space Convective cloud precipitation in Nagqu region of the Tibetan Plateau.the spatiotemporal distribution of particles in each phase state simulated by Lin scheme shows that the three phase state particles in solid,liquid and gas are distributed at different elevation levels,and their distribution position does not change significantly with height.The extreme value center represents the maximum value of ground precipitation,and the mass density of water vapor in the precipitation process reaches 9g/kg.in Lin parameterization scheme,cloud water contributes the most to precipitation in terms of rain water source term,snow source term and graupel source term in the cloud microphysics process.Condensation and collision growth are the main processes of ice phase particle growth,as well as important processes of precipitation generation.From the evolution characteristics of microphysical processes,it can be seen that ice particles play a very important role in the whole process of precipitation on the plateau.The melting of graupel plays an important role in the formation of precipitation,but the melting of snow has a small contribution to precipitation.(4)through using the relative discrete degree of cloud droplets spectral sensitivity experiments,again on August 7,to simulate the process of cloud precipitation found relative discrete degree of cloud droplets spectral decrease with the number of cloud droplets concentration solution correlation with the precipitation and surface temperature of the observation better than the other two schemes,three schemes of 2 meters temperature simulation are relatively is not very good.And it can be found that the relative dispersion of cloud drop spectrum decreases with the concentration of cloud drop number,which can reduce the mixture ratio of cloud water on the plateau,thus reducing the cloud water content.By studying the physical process of cloud precipitation over the Qinghai-Tibet Plateau,we can understand the unique characteristics of cloud and precipitation over the Qinghai-Tibet Plateau.Moreover,through model simulation,we can deeply understand the characteristics of the unique cloud microphysical processes on the Qinghai-Tibet Plateau and deepen our understanding of cloud microphysical processes in Nagqu area of the Qinghai-Tibet Plateau.The sensitivity experiment of relative dispersion of cloud droplet spectrum is helpful to improve the simulation level of mesoscale model in Nagqu area of Qinghai-Tibet Plateau.