远距离台风暴雨过程的正/斜压不稳定

Barotropic/Baroclinic Joint Instability in the Storm Rainfall Far from a Typhoon

利用正 /斜压联合不稳定计算方法,分析了由 9711号台风引起的远距离台风暴雨(实况及MM4模拟结果 )过程中不同时段、不同位置的正 /斜压项。结果表明:台风暴雨初始时段的降水主要由台风系统本身正压不稳定扰动引起,随着台风与西风带系统的结合,其南北部出现了 2个雨区,均是正 /斜压联合不稳定的产物;北部雨区的斜压不稳定较明显,且有随高空急流的非纬向性增强而增强的趋势。

Application of the analysis and calculation of the barotropic/baroclinic joint instability in the storm rainfall far from a typhoon are introduced.Based on simulations and observations,analyses and calculations of barotropic and baroclinic items were carried out at different time levels and positions in the storm rainfall induced by 9711 typhoon.Results show that precipitation at the initial stage was basically caused by barotropic disturbances,and two rainfall areas,caused by the barotropic/baroclinic joint instability,occurred to the south and north of the typhoon circulation along with the coupling of the typhoon and the westerly trough.Especially,the baroclinic instability was more obvious in the north rain area,and had a strengthening trend with the non-zonal enhancement of the high-level jet.So we can conclude that the storm rainfall far from the typhoon is the offspring of the barotropic/baroclinic joint instability, and the strengthening of the baroclinic instability is closely associated with the non-zonal high-level jet.