Research On The Evaluation Of The Forecast Effect Of Severe Convective Weather In Jianghuai Based On Dual Polarization Rada

Severe convective weather is one of the important disastrous weather affecting Jiangsu Province,which often causes great casualties and property losses.The cloud microphysics parameterization scheme in the numerical model is very important to the influence of severe convective weather forecast.To clarify the difference of the simulation ability of the microphysics parameterization scheme for a specific severe convective weather system has a good application value for the improvement of precipitation forecast during severe convective process.Aiming at the severe convective weather system in Jiangsu region under the background of northeast cold vortex,this paper takes advantage of the dual-polarization radar data which can distinguish various types of water condensate information.The influence of different microphysical parameterization schemes of WRF（Weather Research&Forecasting Model）on the forecasting of severe convective weather systems such as heavy precipitation and strong wind is analyzed in order to better understand the evolution mechanism of severe convective weather in Jiangsu Province under the background of cold vorticity.Then the numerical prediction effect of severe convective weather in Jiangsu region can be improved.In this paper,the large-scale circulation background and microphysical characteristics of two strong convection processes are analyzed by using reanalysis data and dual polarization radar data.The results show that the convection develops deeply in the two strong convection processes,and the height of strong echo exceeds the height of-10℃isotherm（about 7 km）in the core area of convection where the echo intensity is greater than 50 d BZ.The strong precipitation process mainly shows the characteristics of large concentration and large particle size raindrops.The strong echo height of strong wind process is higher,and the upper layer hail is widely distributed.In this paper,five different microphysical parameterization schemes of the model are selected respectively to simulate and compare the two cases.The comparative analysis of numerical simulation results shows that each scheme can well simulate the difference of water particle size between precipitation and strong wind cases,so that the simulation characteristics of each scheme reflected by the radar reflectance are similar,but the polarization quantity simulation of each scheme is significantly different.The radius of water particles simulated by WDM6（WRF Double-Moment 6-class）scheme is too small.The polarization quantity simulated by WDM6（WRF Double-moment 6-Class）scheme is significantly smaller than that of radar observation,and the precipitation forecast is also significantly weaker.The particle size simulated by WSM6（WRF Single-Moment 6-class）scheme is larger than that simulated by WSM6（WRF Single-moment 6-class）scheme,which results in that the polarization quantity simulated by WSM6 scheme is obviously larger than that observed by WSM6 scheme in two cases.In MY（Milbrandt-Yau）and Morrison schemes,the Z_DR of low layer is strong.In contrast,the Z_DR and K_DP values of Thompson scheme in the two simulations are most close to the observed values,the vertical structure characteristics of Z_DR are more consistent with the observed characteristics,and the probability distribution diagram shows that the matching relationship between Z_DR and Z_H is also more consistent with the physical laws presented by the observation.In order to further clarify the possible reasons for the difference in the simulation results of polarization quantity caused by different microphysical processes,the sensitivity test analysis of particle number concentration and mass mixing ratio was carried out for precipitation cases.The test results showed that the simulation results of microphysical parameterization scheme could be improved by changing particle number concentration or mass mixing ratio,especially Morrison scheme.The normalized frequency distribution can be obtained by changing the mass mixing ratio of rainwater particles.In the end,the paper selects different starting times to simulate the two cases for several times.The comparison results show that the characteristics of the simulation results of each scheme have good stability for different starting times.Whether it is heavy precipitation or strong wind event,the vertical structure of liquid and ice particle content in Thompson scheme can best reflect the difference between dry and wet in two cases,and its simulation value of snow particle content is higher than that of other schemes.However,graupel particles are significantly smaller than other schemes,and the improvement in the simulation accuracy of upper water condensate may be the main reason for the optimal simulation effect of Thompson scheme.