Numerical Simulation Of Macroscopical And Microcosmic Features Of Hail-cloud In West Shandong Province In Summer

According to the real-time observation analyze and numerical simulation, twosevere hailstorms occurred in Shandong province on July 18th, 2002 and July 12th,2005 were carefully studied. The paper researched the environmental distinction, thedynamic mechanism and cloud microphysics structure. Finally a conceptual mode oftypical hailstorm in West Shandong Province were came up.The result shows that the low vortex in high altitude, the shear in minimumaltitude and cold front on surface were the large-scale effect system. And meso-scalebackground field also provided favorable conditions for the storm. Favorable triggermechanism existed in wind vecters before hailing. That is, the coupling of strongdivergence on cloud top and convergence on cloud base caused intense upwardvelocity, which would been gradually decreased owing to the effect of draggingfunction of hailing etc brought. At the beginning, hail-cloud appear in front of themain draft, higher than the largest ascending velocity area in vertical. Then clouddeveloped along the place where the updraft flow tamed into downdraft divergentflow. In the middle and low levels of the developing period, a semicircle echo gapappeared at the back space of the hail-cloud, where main updraft exited. At thematurity period, a hook shaped echo appear at the right back of the hail-cloud in themiddle and low levels. Echo wall, BWER, overhang echo exited in the vertical plane.Hail embryo source appeared in front of the main draft, higher than the largestascending velocity area in vertical, where the updraft flow turned into downdraftdivergent flow. The surrounding temperature is near -20℃. As the strength of theupdraft and downdraft divergent flow, some particles were flowed to a far area inhorizontal direction to form enormous anvil cloud; some were flowed with thedowndraft flow to a lower level to meet the convergent flow and into the main draft,and then the downdraft. Thus, particles grow up in this circulation between updraftand downdraft and into large hail particles. Embryo curtain exited at this area. Echowall was also here at mature period.