Simulation Study On The Characteristics Of Charge Structure In Guangzhou "May 7" Rainstorm Dominated By Warm Cloud Precipitation

In order to understand the characteristics and causes of charge structure in convective cells dominated by warm cloud precipitation,WRF model with electrification and discharge parameterization scheme was used in this paper to simulate the sudden rainstorm dominated by warm cloud precipitation in Guangzhou on May 7,2017.The simulation effect is determined by comparing the simulation results with the actual observation data.This paper analyze the characteristics and causes of charge structure of a monomer in the process of maturation,and discuss the variation characteristics and its causes of the bottom positive charge region of the monomer with different convection.In addition,the influence of induction charging mechanism in the strong convection cell on the bottom positive charge area is discussed.The main conclusions are as follows:(1)The height of the single cloud top during the extreme heavy rain dominated by warm cloud precipitation is lower than the typical convective process in the same area,and the convection intensity is weaker.In the different convective cells,the strong echo area is formed by heavy raindrops,with a small range and a lower top.There is less supercooled water transported above the 0? layer,which is not conducive to the formation of ice phase particles,and the low cloud water content in the mixed phase region reduces the collision between snowflakes and supercooled water.So,the content of small and large ice particles is small.The ice particles with the most content are snowflakes,followed by graupel,ice crystals,and hail.(2)In strong convection monomer,the net space charge distribution in the convective region presents a tripolar structure,But the upper positive charge area is smaller and the charge density is weaker.Compared with the strong convection cell,the net space charge distribution of monomer in the weak and moderate convection is only in the middle negative charge region and the bottom positive charge region.In the different convective cells,the middle negative charge region is dominated by ice crystals and snowflakes with negative charge,the bottom positive charge region is dominated by graupel particles with positive charge and raindrops with positive charge,and the upper positive charge region is dominated by snowflakes with positive charge in the strong convection monomer.In the weak convection monomer,the ice phase particles fall below 0 ? layer,and the warm cloud area is thick in this process.A large number of ice phase particles melt into raindrops completely,which results the raindrop charge in the weak convection monomer is larger than that of the medium convection and strong convection monomers.(3)In the different convective cells,the bottom positive charge region is mainly formed by positively charged graupel particles and positively charged raindrops.The difference is that the bottom positive charge region is dominated by graupel particles in the medium convection and strong convection monomers,and by positively charged raindrops in the weak convection monomer.Compared with the typical hailstorm process in inland plateau in China,the charge density and distribution range of bottom positive charge area are smaller in the strong convection monomer,but the same is that both processes are dominated by graupel particles,and the hail and raindrops with positive charge play a role in promoting.Different from this process,the thickness of warm cloud area is smaller in the process of hailstorm,and the ice phase particles quickly fall to the ground and melt into charged raindrops less,so the positive charge area at the bottom of hailstorm disappears in the wea convection monomer.(4)The electrification in the cloud is weak,and non-inductive electrification is the main.The non-inductive electrification is mainly based on the positive electrification rate below-15°C in the convection zone,and the inductive electrification rate is dominated by the negative polarity in the convective zone,which coincides with the main non induced electrification region.The strong electrification zone and the discharge zone overlap,mainly concentrated in the convection zone of 35-50 d BZ above the echo center.In the mature stage of strong convection monomer,when the inductive charging mechanism is turned off,the positive charge area in the upper part of the strong convection zone becomes smaller,the negative charge area in the middle and the positive charge area at the bottom become larger,and the negative charge area in the middle and the positive charge area at the bottom of the convection periphery become smaller.