锋面涡旋诱发南海热带气旋Noguri(2002)的数值试验

NUMERICAL STUDY ON TROPICAL CYCLONE NOGURI (2002) FORMATION IN THE SOUTH CHINA SEA ASSOCIATED WITH A FRONTAL VORTEX

利用WRF_ARW模式,对锋面型涡旋诱发南海强热带风暴Noguri(2002)的生成过程进行模拟研究。通过对动力学和热力学物理量的诊断分析,讨论了锋面型初始涡旋诱发热带气旋(TC)的可能途径和机制。结果表明:该类型TC与热带扰动诱发TC的过程相类似,强对流单体(如积云塔)与环境场间的相互作用发挥重要作用,而这些对流尺度系统的活动受较大尺度系统调控。在环境场强垂直风切变情况下,初始涡旋在发展过程中,表现为垂直方向上涡旋结构由倾斜向垂直演变的过程,涡度、螺旋度和水汽场均存在若干次振荡。进一步分析表明,水汽和对流循环的反馈对涡旋的振荡发展很重要,且与环境场垂直风切变的强弱变化有着密切的联系。

By using the WRF_ARW model, we simulated a frontal-type severe tropical storm Noguri （2002） to learn about its possible genesis mechanisms. Similar to the traditional TC genesis events in the tropics, the evolution of its vorticity, helicity and moisture fields experience several oscillations. Under strong vertical wind shear associated with a frontal system, the initial storm developed from a vertical tilting to a nearly upright structure. After close examinations of both dynamical and thermodynamical processes, we found that feedbacks between convection and PBL moisture charge-recharge are important for the oscillation of the vortex, which has close connection with the strength change of vertical wind shear.