Critical-level crossing of rossby-gravity wave-packets in a linear-shear,stratified flow |
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| Authors: | Hiroyasu Ando |
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| Institution: | Tokyo Astronomical Observatory, University of Tokyo , Mitaka, Tokyo, 181 |
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| Abstract: | Abstract The propagation of Rossby-gravity waves, which are of astronomical interest near the critical level (or corotation point), is considered in a linear-shear, exponentially stratified flow by means of a ray tracing method. It is shown, using the analytic solutions for the stream function, that for a Richardson number J > 1/4 a wave-packet can cross the critical level in a finite time. In the unstable stratified case (J < 0), it cannot cross the critical level for large |J| (J < 0), but may do so for some intermediate |J| values. Based on the above results, the possible existence of the regular normal mode with a discrete point eigenvalue in the continuous spectrum is discussed for bounded systems. |
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| Keywords: | Couette flow wave-packet critical level normal mode |
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