Mesoscale Study About The Contribution In Huabei Rainstorm On Interaction Between Typhoon And Mid-Latitude System

We made large numbers of statistical calculation and study about typhoon rainstorm from 1949 to 2000. The results shows: the decade difference of typhoon rainstorm was very remarkable.and it's times was most in 1960',Ieast in 1980'. In the 52 years,there are 51 rainstorms resulting from typhoon .about 1 rainstorm each year, most of them occurred in the summer( July and August).its landing place was mostly in JiangSu,ZheJiang,Fujian. Interaction,sub- interaction,non- Interaction turned and turned about 58.8%,23.5%,17.6%.In order to make clear the interaction between typhoon and mid-latitude system,we made numerical simulation test and physical diagnosis of 9608 typhoon in 1996.lt is found that in low layer,the connection between the subtropic high and typhoon periphery enhanced the low-level jet and transportation of water vapour. The south-north trough was formed and strengthened by the movement of cold air from NE to SW.In high level.upper trough on South Asia High and its north and release of potential heat made it maintained,therefore divergence at upper layer was enhanced ,and high jet was built. The interaction provided impetus condition for typhoon rainstorm through upper level convergence at the low layer and marked divergence at upper layer.some advantageous conditions resulted in the large-area rainstorm.Firstly.in large-scale background,typhoon conbined with westerly trough on mid-latitude and made long- time instability area on HuaBei because cold air infalling continuably from DongBei ;secondly,low level jet provided a large number of persistent vapor;finally, the puissant go-up air flow was carried through strong convergence at the low layer and marked divergence at upper layer.We estimated the conditional symmetry instability by absolute and geostrophic momentem(Mg) and comparative potential temperature. In this rain process, there was the symmetric and convection instability.By filtering calculation, the symmetric and convection instability can result in inertia-gravity wave.In high level ,its scatter connect with the symmetric instability ;in low level,its non- scatter connect with the convection instability. The symmetric and convection instability played the important role in increasing rain.By Hoskins's dynamics frame of potential vorticity.diagnosis was performedabout vertical and inclined instability of potential vorticity when typhoon 9608 was bringing heavy rains.On the heavy rain time, potential vorticity of vertical press transformed partially into inclined potential-vorticity on low level. On the latter time of heavy rain .potential vorticity of inclined press transformed partially into vertical potential-vorticity on low level.