Modulational instability of Rossby and drift waves and generation of zonal jets

Details Modulational instability of Rossby and drift waves and generation of zonal jets Modulational instability of Rossby and drift waves and generation of zonal jets

2009-05-14

arxiv.org/abs/0905.2243v1

J. Fluid Mech. 654, 207-231, 2010

Nonlinear Sciences

Chaotic Dynamics

26 pages, 30 figures

Scientific paper

10.1017/S0022112010000510

We study the modulational instability of geophysical Rossby and plasma drift waves within the Charney-Hasegawa-Mima (CHM) model both theoretically, using truncated (four-mode and three-mode) models, and numerically, using direct simulations of CHM equation in the Fourier space. The linear theory predicts instability for any amplitude of the primary wave. For strong primary waves the most unstable modes are perpendicular to the primary wave, which correspond to generation of a zonal flow if the primary wave is purely meridional. For weaker waves, the maximum growth occurs for off-zonal inclined modulations. For very weak primary waves the unstable waves are close to being in three-wave resonance with the primary wave. The nonlinear theory predicts that the zonal flows generated by the linear instability experience pinching into narrow zonal jets. Our numerical simulations confirm the theoretical predictions of the linear theory as well as of the nonlinear pinching. We find that, for strong primary waves, these narrow zonal jets further roll up into Karman-like vortex streets. On the other hand, for weak primary waves, the growth of the unstable mode reverses and the system oscillates between a dominant jet and a dominate primary wave. The 2D vortex streets appear to be more stable than purely 1D zonal jets, and their zonal-averaged speed can reach amplitudes much stronger than is allowed by the Rayleigh-Kuo instability criterion for the 1D case. We find that the truncation models work well for both the linear stage and and often even for the medium-term nonlinear behavior. In the long term, the system transitions to turbulence helped by the vortex-pairing instability (for strong waves) and by the resonant wave-wave interactions (for weak waves).

Affiliated with

Also associated with

No associations

Rating

Modulational instability of Rossby and drift waves and generation of zonal jets does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Modulational instability of Rossby and drift waves and generation of zonal jets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Modulational instability of Rossby and drift waves and generation of zonal jets will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-399780