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在层结旋转流体中,当背景场为轴对称涡旋时,用WKB方法导出了扰动运动的波作用密度守恒.从这一守恒方程出发,得到了涡旋中扰动不稳定的必要条件.在一般情况下,这一条件为:当涡旋中扰动的周向相速度与基本气流的旋转角速度相等,即存在共转圈时,扰动可能发展。 据此,文中以大气中的台风为例,分析了其中扰动的发生发展条件,并根据实际资料推出台风中的垂直环流将是双圈的,为台风眼的存在提供了一种可能的解释。
In the stratified swirling fluid, when the background field is an axisymmetric vortex, the WKB method is used to derive the conservation of the wave action density of the disturbing motion. From this conservation equation, the necessary conditions for the instability of the swirl are obtained. In general, the condition is that the perturbation may develop when the velocity of the circumferential phase perturbed in the vortex is equal to the rotation angular velocity of the basic gas flow, that is, when there is co-rotation. Therefore, taking the typhoon in the atmosphere as an example, the conditions for the occurrence and development of the disturbance are analyzed. According to the actual data, the vertical circulation in the typhoon will be double circles, which provides a possible explanation for the existence of the typhoon eye.