垂直切变基流中的非平衡不稳定  

NON-EQUILIBRIUM INSTABILITY IN VERTICAL SHEAR FLOW

作　　者：安洁[1,2] 张铭[2] 

机构地区：[1]空军装备研究院航空气象防化研究所,北京100085 [2]解放军理工大学气象学院大气环流与短期气候预测实验室,江苏南京211101

出　　处：《热带气象学报》2009年第1期48-58,共11页Journal of Tropical Meteorology

基　　金：国家自然科学基金项目(40575023);青年科学基金项目(40705020)共同资助

摘　　要：采用计算横波型扰动波谱和谱函数的方法,研究了当基本气流具有垂直线性切变、层结参数为常值时横波型扰动的不稳定,给出了不稳定扰动的结构,讨论了不稳定的性质。发现:对于三支波动连续谱区互不重叠的天气尺度情况,若此时出现不稳定扰动,其性质属于纯涡旋波的准地转不稳定,与Eady模态类似,是Rossby波的斜压不稳定;在中α尺度中高端,其不稳定性质仍是纯涡旋波的不稳定,即准平衡的斜压不稳定;在中α尺度低端则出现了第一类混合波的非平衡不稳定,包括涡旋-逆传重力惯性混合波的不稳定和涡旋-顺传重力惯性混合波的不稳定,前者低层体现了涡旋波的特点,高层体现了重力惯性波的特点,后者反之;在中β尺度波段,若存在不稳定则均为非平衡的涡旋-重力惯性混合波不稳定,其包括第一类和第二类混合波的不稳定,后者低层体现重力惯性波的特点,中层体现涡旋波的特点,高层则又体现了重力惯性波的特点。The character and structure of instability of transversal wave disturbance is studied in this paper by using calculating the spectrum and spectral function of the transversal wave disturbance. It is assumed that basic flow has linear vertical shear and stratification parameter and Coriolis parameter are constant. It can be concluded as follows. The synoptic scale on which the zone of continuous spectrum of three waves does not overlap each other, instability, if appears, is quasi-geostrophic from pure vortex wave, like the Eady mode, and is the baroclinic instability of Rossby wave. For the long wave band of meso- a scale, instability is also of pure vortex wave, that is, baroclinic in quasi-equilibrium. In the short wave band of meso- a scale region, however, it shows the first class non-equilibrium instability of mixed wave, including the vortex-upwind gravitational inertia wave instability and the vortex-downwind inverse gravitational inertia wave instability. The former has the character of vortex wave in low layers and that of gravitational inertia wave in high layers, and the latter is directly opposite to it. In the meso-β scale region, if instability exists, it is the nonequilibrium mixed vortex-gravitational inertia wave, including the first class and second class instability of mixed wave, and the latter has the character of gravitational inertia wave in low layers, that of vortex wave in middle layers, and that of gravitational inertia wave in high layers.

关 键 词：不稳定 非平衡 横波型扰动 谱函数 涡旋.重力惯性混合波 

分 类 号：P433[天文地球—大气科学及气象学]