Shandong Province, Hail, Cloud Macro And Micro Characteristics Of Observation And Numerical Simulation Study

Making the most of multi- exploration data, such as Doppler radar, satellite cloud image, MICAPS, sounding data and numerical model, thrice processes of hailstorms occurring i n S handong province o n 9,2002 a nd 6,2003 w ere c arefully st udied. T he paper reasoned out the dynamic mechanism and environmental distinction resulting in the hailstorms by analyzing observation data and studied the micro-physical mechanism causing the growth of hail by utilizing a 3D Hail-category Hailstorm Model.Numerical seeding was simultaneously made. Finally a conceptual mode of typical hailstorm and better seeding suggestion were came up.The outcome from analyzing observation data showed that cold vortex or tough was the main large scale system effecting the hailstorms. Cold air came down due to moving southward of the synoptic system and deep southwest airflow was transported into hailing area. As a result, large-scale unstable layer in troposphere came into being. The coupling of the meso-scale low pressure and divergence zone of upper jet caused strong upward motion.For violent and long time hailstorm, stronger wind shear was important environmental distinction. Feasible water vapor condition was also favorable environmental condition for producing bigger hailstone. Radar echo showed many typical characters,such as weak echo area,hook echo and overhang echo on echo intensity. Head wind area, mesocyclone, convergence and divergence on echo velocity were also displayed.The conclusion of numerical simulation showed that favorable trigger mechanism existed in wind vecters before hailing. That is,the coupling of strong divergence on cloud top and convergence on cloud base caused intense upward velocity ,which would been gradually decreased owing to the effect of dragging function that the factors of momentum transfer between upper atmosphere and lower layer and hailing etc brought. Circular flow field in cloud was the main dynamic mechanism causing growth of hail. Hail embryo mostly distributed above subsequent rising velocity beside main one and basically got growth by collecting cloud water. Hail embryo chiefly derived from frozen drop, In addition, snow converted into hail and sleet embryo by collecting cloud water and rain water, so part of sleet embryo was also the source of hail embryo.The outcome of numerical seeding discovered that the bigger hail dwindled in numbers, however small hail and sleet increased or both decreased in numbers after seeding. The cause lied in the fact that the accretion efficiency of cloud water and rain water by hail sharply reduced and the accretion efficiency of dry growth also reduced, on the other hand , detention time of hailembryo in cloud cut short.So hail on the ground was mostly sleet hail or still ice crystals in cloud.On the basis of compositive analysis and theory research predecessors had made, a conceptual mode of typical hailstorm was came up.The description was as follows. Large-scale convergence rising airflow emerged in cloud base, corresponding divergence existed in cloud top.The rising velocity reached maximum in middle-level of troposphere, gradually decreased above the layer.For supercell with strong environmental wind, the asending airflow appeared declining. Upper cloud pulled out enormous anvil cloud with wind aloft. Anvil cloud was composed of little ice crystals and snow. Downward flow that emerged at the back of clouds gradually developed into cloud base, at the same time, hailstone was carried to ground from both sides of clouds with downward flow.