中尺度对称不稳定和横波不稳定的波动性质
投稿时间:2005-11-29  修订日期:2006-10-08  点此下载全文
引用本文:
摘要点击次数: 600
全文下载次数: 634
作者单位
沈新勇 南京信息工程大学 江苏省气象灾害重点实验室, 江苏 南京 210044 
倪允琪 中国气象科学研究院, 北京 100081 
丁一汇 国家气候中心, 北京 100081 
基金项目:江苏省气象灾害重点实验室资助项目(KLME050201);国家重点基础研究发展计划项目(2004CB418301);江苏省自然科学基金资助项目(BK2005141);国家自然科学基金重点资助项目(40433007);上海台风研究基金课题(2004)
中文摘要:使用纬向线性以及非线性切变基流下中尺度扰动的Boussinesq近似方程组,讨论了两种典型的中尺度扰动发生对称不稳定或者横波不稳定时,其不稳定的一些特征以及扰动的波动性质。研究结果表明:(1)对于扰动的等位相面平行于基本气流方向的对称性扰动来说,对称不稳定的波动实质是沿着与基本气流方向相垂直的方向传播的重力惯性内波的不稳定。基流二次切变对于中尺度对称扰动来说是一个不稳定因子,并且驱动不稳定的中尺度对称扰动在南北方向传播;(2)对于扰动的等位相面垂直于基本气流方向的横波性扰动来说,在基本气流为常数或者只具有线性切变的情况下,此时根本不存在涡旋Rossby波,横波不稳定的波动实质则是沿着基本气流方向双向传播的重力惯性内波的不稳定。如果考虑基本流场的风速存在二次切变或者非线性切变时,此时就会产生一支新的波动(涡旋Rossby波),涡旋Rossby波相对于基本气流U0是单向传播的,涡旋Rossby波产生的物理根源是基本流场的风速U二次切变(β*=Uzz≠0),此时横波型不稳定可能是混合的涡旋Rossby——重力波的不稳定。实际大气中,涡旋Rossby波对于中-β尺度对流云核、暴雨团等天气系统的发生、发展和演变的物理机制具有极其重要的意义。
中文关键词:对称不稳定  横波不稳定  波动性质  涡旋Rossby波
 
Wave Properties of Mesoscale Symmetric and Transversal Instable Disturbances
Abstract:Using the Boussinesq approximation equations for meso-scale disturbances in zonally linear and non-linear shear flows a study is undertaken of the unstable features and wave properties of two typical meso-scale unstable disturbances(i.e.symmetric and transversal instabilities. Results suggest that:1)for symmetric disturbances with its iso-phase plane parallel to the basic flow,the instability of the disturbance is actually the instability of the internal inertial gravity wave propagating in a direction perpendicular to the basic flow.The second-order shear of the basic flow represents an instable factor for the symmetric disturbance,and drives the unstable mesoscale disturbance to travel in the meridional direction;2) for traversal disturbance with its iso-phase plane perpendicular to the basic flow no vortex Rossby wave exists at all when the basic flow is constant or only linearly sheared and the instability of the traversal disturbance is actually the instability of the internal inertial gravity wave propagating simultaneously in two opposite directions with respect to the basic flow.With a second-order or nonlinear vertical shear of the basic flow taken into account,a new kind of wave(vortex Rossby wave) occurs and it propagates in one direction with respect to basic flow0 and originates physically in the second-order shear of windspeed (β*=zz≠0).In fact,the instability of the traversal disturbance may be the instability of mixed vortex Rossby ——gravity wave.In the real atmosphere vortex Rossby wave is crucial to the genesis,development and evolution of meso-β convective cloud nucleus and rain cores.
keywords:symmetric instability  traversal instability  wave property  Vortex Rossby wave
查看全文  查看/发表评论  下载PDF阅读器