大尺度涡旋的正压不稳定

用极坐标中线性化的正压涡度方程，将大尺度圆形基流上扰动的稳定性问题化为广义特征值的问题，得到了扰动振幅增长率沿方位角方向波数的关系。然后以不稳定模态的扰动流函数场作为初始场，在强、弱两类圆形基流的条件下，用直角坐标中准地转正压模式，分别实施积分时间为６０ｈ的试验。结果在模式大气中，初始扰动均随时间而增幅；强圆形基流的扰动增幅更快，并形成与台风螺旋云系看似有些相近的结构。

BAROTROPICAL INSTABILITY OF DISTURBANCES ON A LARGE CIRCLE VORTEX

he barotropical instability for smaller scale disturbances superimposed on a large scale circle parallel vortex is investigated numerically. The growth rates of the orders of (10-4 10-5) s-1 are found at azimuthal wave numbers between 3. 0 and 10. 0. Then the most unstable mode for the disturbances is taken as the iniial steam function field of a quasigeostrophic barotropical model and two numerical experiments whose integration times equal to sixty model hours are performed for more and less intense vortex. respectively. Results show that the initial small disturbances for the both all develop certainly and that vortex filaments exhibit in the edge of more intense vortex, which is somewhat similar to the observational phenomenon concering the outer structure of tropical cyclone.