A Dual-polarization Radar Observational Study On The Dynamic Process Of A Hailstorm In Guizhou

In order to understand the evolution of the microphysics and dynamic processes and the interaction of the two processes with different stages(development,maturity,dissipation)in hail,based on the catenation of Z_DR column and updraft in convective monomer,this paper cites the Z_DR column definition of existing research,and uses the dual-polarization radar and sounding data from Weining,Guizhou to establish a fuzzy logic identification algorithm of precipitation particle phase which based on Z,Z_DR,KDP,?HV and temperature.Analysis the characteristics of the Z_DR column during three typical hail in 2018,the results as follows:(1)There are interactions between the monomers of squall line system,and the hailfall monomer's Z_DR column with the most obvious characteristics and changes.In the development stage of hailfall monomers,the average and maximum values of the differential reflectivity in the Z_DR column are greater than1.3d B and 2.0d B,respectively,and the maximum value of the positive radial velocity is greater than 15m/s,the number of proportion of graupel is relatively large(conductive to long-time hail)and the maximum is 0.35(2 times increase).In the maturity stage,the maximum value of the differential reflectivity in the Z_DR column is greater than 3.5d B,and the positive radial velocity reaches a valley value of 8.5m/s.In the dissipation stage,the average value of the differential reflectivity in the Z_DR column is less than 1.27 d B,the maximum value is less than2.03 d B,and the proportion of supercooled water increases to 0.5.(2)In the development stage of single cell,the average value of the differential reflectivity in the Z_DR column is greater than 1.25 d B,the maximum Greater than1.6d B,the maximum value of the positive radial velocity is greater than 13m/s,and the maximum number of proportion of graupel is 0.12(3 times increase).In the maturity stage,the maximum value of the differential reflectivity in the Z_DR column is greater than 2.5d B,and the positive radial velocity reaches a valley value of 12.5m/s.In the dissipation stage,the average value of the differential reflectivity in the Z_DR column is less than 1.27 d B,the maximum value is less than2.03 d B,and the proportion of supercooled water increases to 0.18.(3)The combined hail of multiple monomers,the average and maximum increase rates of differential reflectance in the Z_DR column are 34% and 72% during the development stage,respectively.One time before hailstorm,the average and maximum of the differential reflectance in the Z_DR column are greater than 1.8d B and 4.0d B respectively,the maximum of the positive radial velocity is 9.5m/s,and the proportion of the number of graupel particles is 0.29.In the mature stage,the maximum is 3.0d B(variation rate is-25%),the valley of the positive radial velocity is 9m/s(the rate of variation is small).In the dissipation stage,the average is about 1.4d B,the maximum value decreases,and the proportion of the number of supercooled water particle pools increases with the maximum value of0.42.(4)The microphysical process and dynamic process affect each other in hailfall monomers' each stage.In the development stage,the latent heat released by the supercooled water freezes(nucleates)and the condensation of water vapor which near the surface of ice crystals in the Z_DR column,so that the instability of the convection and the updraft are increase,with the phenomenon of the average and maximum value of the differential reflectivity and positive radial velocity in the Z_DR column,and the area of Z_DR column are increasing.A large amount of supercooled water are transported to a few kilometers above the 0? layer height by strong updraft,which promotes the growth of ice crystals and hail embryos.As the updraft increases,supercooled water increases,which lead to the more hail embryo(longer duration of hailfall),with the phenomenon of the proportion of graupel increased sharply.In the maturity stage,a few big raindrops enter the updraft during the precipitation process,which caused the maximum value of the differential reflectivity to peak in the Z_DR column.As the graupel(hail embryo)attaches the supercooled water to form hail,some hail particles absorb the latent heat from the environment during the precipitation process,which result the downdraft weakens the intensity of the updraft and the transport of supercooled water decreases,with the phenomenon of the maximum value of the positive radial velocity in the Z_DR column appears a trough and the rate of increase of graupel is decreases.In the dissipation stage,the drag of precipitation particles promotes the cloud to dissipate and the updraft to weaken,with the phenomenon of the average and maximum values of the differential reflectivity in the Z_DR column and the area of the Z_DR column all decrease.As the weaken of updraft,the height of supercooled water can be transported is decreases,the microphysical processes(attachment,collision)are decreases,the number of proportion of supercooled water is increase.