地形对正压大气Rossby波非线性相互作用的影响
The Influence of Topography on the Nonlinear Interaction of Rossby Waves in the Barotropic Atmosphere
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摘要: 本文采用弱非线性近似,推导出地形和Ekman摩擦共同作用下连续谱正压Rossby波的非线性时空演化方程。根据这组方程,我们研究了窄角谱Rossby波包的波波相互作用问题,当一个大振幅Rossby波包通过大气传播时,如果它的振幅超过某个阈值,非线性相互作用会使一个尺度比它大的Rossby波包和一个尺度比它小的Rossby波包的振幅随时间指数增长,这两个次级波的本征频率会发生改变,Ekman摩擦、频率不匹配、地形坡度以及波包的空间演变共同决定了主波振幅的阈值及次级波本征频率的改变量。Abstract: In the frame of weak nonlinear theory,a set of equations depicting the nonlinear iateractioas of barotropic Rossby waves are derived,the topography and Ekman friction are involved in the equations. Starting from the equations, we investigate the interaction of three Rossby wave packets with narrow-spread in wave vectors, When an intense primary pump Rossby wave with amplitude larger than a threshold propagates through the atmosphere, the amplitude of one Rossby wave packet with scale greater than the primary one and one Rossby wave packet with scale smaller than the primary one grow exponentially through three wave interactions, the intrinsic frequencies of the secondary waves can be varied. The threshold and the variation of the intrinsic frequencies of the secondary waves are related to the Ekman friction frequency dismatch,topography and spatial evolution of the secondary Rossby wave packets.
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Key words:
- topography /
- Rossbp waves /
- non-resonant parametric instability
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