斜压气流中波包的演变及其对外压不稳定波的激发
EVOLUTION OF WAVE PACKET AND THE EXCITATION OF UNSTABLE BAROCLINIC WAVES IN BAROCLINIC FLOW
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摘要: 把斜压气流中的短波槽看成波包,并把波包作为准地转模式的初值进行研究,发现波包的结构对其演变有重要影响,初始阶段急流轴下面向西倾斜的波包能够获得较快的发展,而向东倾斜的波包则是衰减的,这与WKBJ方法得出的结论[1]是一致的,但是无论西倾还是东倾的波包,除了其自身随时间的演变外,还会激发出斜压不稳定波动,而且随着扰动的发展,不稳定斜压波会逐步在扰动中占主导地位。由此可以解释某些中纬度气旋的发生发展问题。Abstract: As short upper trough is considered as a wave packet in baroclinic flow, the evolution of the wave packet is investigated as an initial value problem in a quasi-geostrophic model, it is found that evolution of the wave packet depends on the packet' s structure. When the wave packet under the jet stream inclines to the west at initial stage. it will develop quickly. While the wave packet under the jet stream inclines to the east. it will be decaying. These conclusions are consistent with those obtained from WKBJ method [1] However, whether the wave packet is west tiltor east tilt, it can excite unstable baroclinic long waves in the baroclinic flow besides the evolution of the wave packet itself. Furthermore, along with the evolution of disturbances the most unstable baroclinic wave becomes a dominator. These results may be used to explain the generation and development of some midiatitude cyclones.
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Keywords:
- Baroclinic flow /
- Evolution of wave packet /
- Unstable baroclinic waves
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