大气横波型扰动连续谱的结构  

The Structure of Continuous Spectrum of Transversal Perturbation Wave in Atmosphere

作　　者：张铭[1] 安洁[1,2] 

机构地区：[1]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,南京211101 [2]空军装备研究院航空气象防化研究所,北京100085

出　　处：《大气科学》2008年第6期1401-1410,共10页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金资助项目40575023

摘　　要：采用数值方法计算了当基本气流有垂直线性切变、层结参数为常值时横波型扰动的谱点和谱函数,并将数值计算的结果与理论分析作了对照和讨论。当三支波动连续谱区相互不重叠时该计算结果与理论分析完全一致,但当发生连续谱区重叠时则须采用谱函数重组的方法来得到连续谱的结构。重组的基本原则是在波谱重叠区对计算得到的谱函数作预处理后,再对频率相邻的谱点和谱函数进行滑动平均,并将该滑动平均后的结果作为重组后的谱点和谱函数。分析该重组后的谱函数可知,此时扰动结构呈现涡旋-重力惯性混合波的形式,出现了新波型。在连续谱三波重叠区域,该混合波的谱函数在对流层中层有涡旋波的临界层并体现了涡旋波的性质,在对流层的上、下层则分别有顺、逆传重力惯性波的临界层并体现了重力惯性波的性质。The spectrum and spectral function of the mesoscale wave are studied by using nonstatic quasi-two-dimensional Boussinesq equations. It is supposed that basic flow is only the function of z. The equations are linearized with definite condition, and then the initial value and boundary value problems are changed into the eigenvalue problem of generalized matrix after assuming normal mode solution. The spectrum and spectral function of transversal disturbance in atmosphere are studied by using the numerical method when the vertical linear shear of basic flow exists and the stratification parameter is constant. The results of numerical calculation and theoretical analysis are discussed and compared. When the continuous spectrum areas of three waves do not overlap, the numerical solution is consistent with the analytic solution. But when continuous spectrum areas overlap each other, the structure of the continuous spectrum would be gotten by using the method of recombining spectral function. The basic principle of recombining is that, in the continuous spectrum overlapping area the spectral function of numerical solution is preprocessed, and then the running mean is calculated for the frequency consecutive spectrum and spectral function, and the running mean results are regarded as spectrum and spectral function after recombination. From the results of the spectrum and spectral function after recombination it can be seen that the structure of the disturbance is a hybrid wave of vortex wave and inertia-gravitational wave, that is, new wave mode appears. In the overlapping area of three waves of the continuous spectrum, the spectral function of the hybrid wave has the critical layer of vortex wave in the middle troposphere, which shows the character of vortex wave, and have the critical layers of inertia-gravitational waves along and against the basic flow propagation in the upper troposphere and the lower troposphere, respectively, which shows the character of inertia-gravitational wave.

关 键 词：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]