A Numerical Simulation On Hail Formation Mechanisms And Hail Suppression In Hubei Baokang

There were many hail processes happening every year in Hubei Baokang. It brought huge damage to crops especially tobacco leaves in the locality. In order to make a good effect of hail suppression, this paper studied the hail formation mechanisms and hail suppression in Hubei Baokang.According to the statistical analysis to hail falling in Baokang, hail falling focused between May to September every year and focused between thirteen to eighteen o’clock in one day, the region of happening hail falling was not well-distributed. Hail processes main happened in four atmospheric circulations:northwest, edge of subtropical high, inner of subtropical high and no type.The three-dimensional convective storm model(IAP-CSM3D) developed by the Institute of Atmospheric Physics (IAP), the Chinese Academy of Sciences was used to simulate the strong convective storm occurred in Hubei Baokang. The character of accumulation zone of supercooled raindrops with the six hailstorm cases in Baokang was analyzed, the results were shown as follows:there are accumulation zones in the formation processes among the six cases hailstorm, the accumulation zones last about seven minutes and with the thickness of1-2km, the hail embryos are mainly frozen drops. The040706hailstorm case whose accumulation zone was and hail falling was very strong also was studied, the simulation results indicate that the accumulation zone is the area wherein hail embryo formation and hail embryo grow up quickly with colliding supercooled rain water, hailstones mainly depend on the processes of collecting supercooled cloud water to grow after formation. The040706,040708,060806and070708hailstorm cases were comparative analyzed, the results showed that:vigorous updraft and high content of supercooled rain water during in accumulation zone period is very important to the formation of hail embryo, but vigorous updraft wherein during the whole hailstrom lifetime is also very important to the formation and growth of hail.The040706hailstorm case’s simulate experiment seeded by AgI showed that, hail amount decreased along with the decrease of rain falling amount after seeding. there were different hail suppression effect with different seeding time, seeding amount and seeding position:there was good suppression effect seeding at hail forming stage, the suppression effect would be bad seeding at hail maturing stage. The suppression effect would be better when the seeding amount increase, the change of suppression effect would be small when the seeding amount increased at a certain extent. The hail suppression would be better in this hail case when the seeding position selected at the maximum value area of supercooled rain water. The hail suppression mechanism was also studied:the number of artificial ice increased with seeding, but the content of supercooled rain water decrease with ice consuming. The numbers of frozen drop raised after seeding, the mean of frozen drop mass and size reduced, the amount of frozen drop transforming to hail also reduced. Hail growth would be restrained with the reducing of supercooled cloud water content after the formation of hail, so the hail would be suppressed.