在正压过滤模式大气中地形和水平扩散对非对称运动形成的作用

THE EFFECTS OF OROGRAPHY AND HORIZONTAL DIFFUSION ON THE GENERATION OF THE ASYMMETRIC MOTION IN THE BARO-TROPIC FILTERED MODELATMOSPHERE

利用考虑地形和水平扩散作用的正压涡度方程,在线性情况下,给出了描写对称运动和反对称运动(都是对赤道来说的)的方程和它们各自的解析解。分析这些解可以看出,不论对于对称运动或反对称运动,解都由三部份组成:一是与初始流场有关的Rossby波;一是以Rossby波波速传播的,与地形和水平扩散有关的行进波;另一是与地形和水平扩散有关的定常波。但是,如初始时刻运动是对称的,则地面拔海高度和水平扩散系数的反对称分布可以引起反对称运动,从而,引起非对称的运动。在定常情况下,则对称的流场,和地面拔海高度、水平扩散系数的对称分布有关,反对称的流场,和地面拔海高度、水平扩散系数的反对称分布有关。最后,还用数值试验,证明反对称地形可以引起反对称运动;还讨论了南北半球的相互影响的问题。

By utilizing the barotropic vorticity equation including the effects of orography and horizontal diffusion, the linearized equation describing symmetric motion and that describing antisymmetric motion, and their analytic solutions, are presented. It can be found from the solutions that no matter what kind of motion may be, each solution consists of three waves, namely, Rossby wave related to initial values, marching wave propagating at Rossby wave velocity and stationary wave. The latter two of them are closely related to orography and horizontal diffusion. However, if the motion is symmetric at the initial instant, then the antisymmetric component of orography and of horizontal diffusion are likely to lead to the generation of antisymmetric motion. In the steady state, the symmetric flow is connected with symmetric orography and horizontal diffusion and the antisymmetric flow with antisymmetric orography and horizontal diffusion. Further, in order to verify the above analysis, three numerical experiments have been made. The results show that antisymmetric orography can produce antisymmetric motion. Finally, the interactions between the atmosphere of the Northern Hemisphere and that of the Southern Hemisphere-are discussed.