本文着重研究大地形对正压大气迭加在非均匀纬向基本气流上挑动演变的影响。用WKBJ方法推导了正压扰动的频率和频散关系以及波作用量所满足的方程。当基本流场定常且存在无限长的东西向山脉时,则有波作用量守恒。据此,获得了正压不稳定的必要条件:即在所考察的平面域内至少在某点或某些点上含地形效应的某一物理量等于零,扰动就可能得到发展。对波包动能的倚时变化的讨论得知,在无摩擦正压纬向非均匀基流的情形,地形对扰动动能并无直接影响,即导波和曳波分别在西风急流的南侧和北侧得到加强,并分别在西风急流的北侧和南侧强度减弱。扰动的发展由扰动的结构所决定。导波和曳波的波长缩短总伴同其轴线倾向于东西向相联系,而它们的波长伸长总是与其轴线倾向于南北向同时发生。还指出,正压扰动的加强(或减弱)与波长的伸长(或缩短)不是必然的联系,它的成立是有条件的。 This paper focuses on the impact of large topography on the evolution of positive atmospheric pressure superimposed on non-uniform latitudinal thrusting. The relationship between frequency and dispersion of positive pressure disturbance and the equation of wave action are derived by WKBJ method. When the basic flow field is steady and infinite east-west range exists, the wave action is conserved. Therefore, the necessary conditions for positive pressure instability are obtained. That is to say, if a certain physical quantity with topographic effect is equal to zero in at least some point or some point in the investigated plane, the disturbance may be developed. The discussion on the variation of kinetic energy of wave package depends on the fact that the topography has no direct effect on the kinetic energy of disturbance in the case of non-friction positive pressure weft non-uniform base flow. That is, the guided wave and the wave are respectively located on the south side of westerly jet stream The north side is strengthened and weakened in the north and south of the westerly jet stream respectively. The development of disturbance is determined by the structure of the disturbance. The shortening of the wavelength of the guided wave and the dragged wave is always associated with its axis in the east-west direction, and their wavelength elongation always occurs at the same time as their axis tends to be north-south direction. It is also pointed out that the strengthening (or weakening) of the disturbance of positive pressure is not necessarily related to the elongation (or shortening) of the wavelength, and its establishment is conditional.