A detailed 3-D hail cloud numerical model and parameterization of mierophysieal processes were described in Part Ⅰ(Hong 1999)of this study.In this part,a hail cloud occurring in Xunyi area.Shaanxi Province on July 8,...A detailed 3-D hail cloud numerical model and parameterization of mierophysieal processes were described in Part Ⅰ(Hong 1999)of this study.In this part,a hail cloud occurring in Xunyi area.Shaanxi Province on July 8,1997 is simulated by the model to analyze mechanisms of hail formation and hail suppression with seeding.The results show that 97% of hail embryos are frozen drops.The seeding experiments with AgI in terms of heights show that if the seeding is made before hail formation,the optimum seeding position is located in the maximum updraft area and its center,i.e.,AgI is seeded in the zone with high water content to be coordinated with maximum zone of the updraft.The seeding makes concentrations of graupel and frozen drop increase and their average mass or size decrease,so that the proportion of conversion from graupel and frozen drop into hail descends greatly,and the mass and concentration of hailstone are decreased to achieve our purpose for hail suppression.展开更多
An artificial cloud seeding experiment was performed over the Japan Sea in winter to show how massive seeding could be effective to mitigate heavy snowfall damage.The results showed that 20 min after cloud seeding,a p...An artificial cloud seeding experiment was performed over the Japan Sea in winter to show how massive seeding could be effective to mitigate heavy snowfall damage.The results showed that 20 min after cloud seeding,a portion of the radar echo beneath the seeding track was weakened to divide the radar echo into two parts.In order to analyze the results,a numerical simulation was conducted by using the Weather Research and Forecasting model verion 3.5.1.In this simulation,the seeding effects were represented as phenomena capable of changing rain particles by accreting cloud ice and snow to form graupel particles and by changing cloud liquid water to snow particles.The graupel particles fell rapidly,thus temporarily intensifying the rainfall,which subsequently decreased.Therefore,the weakened radar echo in the field experiment is deemed to have been caused by the increase in rapidly falling graupel particles.展开更多
文摘A detailed 3-D hail cloud numerical model and parameterization of mierophysieal processes were described in Part Ⅰ(Hong 1999)of this study.In this part,a hail cloud occurring in Xunyi area.Shaanxi Province on July 8,1997 is simulated by the model to analyze mechanisms of hail formation and hail suppression with seeding.The results show that 97% of hail embryos are frozen drops.The seeding experiments with AgI in terms of heights show that if the seeding is made before hail formation,the optimum seeding position is located in the maximum updraft area and its center,i.e.,AgI is seeded in the zone with high water content to be coordinated with maximum zone of the updraft.The seeding makes concentrations of graupel and frozen drop increase and their average mass or size decrease,so that the proportion of conversion from graupel and frozen drop into hail descends greatly,and the mass and concentration of hailstone are decreased to achieve our purpose for hail suppression.
文摘An artificial cloud seeding experiment was performed over the Japan Sea in winter to show how massive seeding could be effective to mitigate heavy snowfall damage.The results showed that 20 min after cloud seeding,a portion of the radar echo beneath the seeding track was weakened to divide the radar echo into two parts.In order to analyze the results,a numerical simulation was conducted by using the Weather Research and Forecasting model verion 3.5.1.In this simulation,the seeding effects were represented as phenomena capable of changing rain particles by accreting cloud ice and snow to form graupel particles and by changing cloud liquid water to snow particles.The graupel particles fell rapidly,thus temporarily intensifying the rainfall,which subsequently decreased.Therefore,the weakened radar echo in the field experiment is deemed to have been caused by the increase in rapidly falling graupel particles.
