Affiliation:
1. Harvard University, Cambridge, Massachusetts
Abstract
Abstract
Interaction among potential vorticity perturbations and propagating internal gravity waves in a horizontally sheared zonal flow is investigated. In the strong stratification limit, an initial vorticity perturbation weakly excites two propagating gravity waves while the density component of the potential vorticity perturbation is significantly amplified, potentially leading to convective collapse. If stratification is sufficiently weak, a strong coupling between vorticity perturbations and gravity waves is found and spontaneous gravity wave generation occurs. This coupling can be traced to the nonnormal interaction between the potential vorticity and gravity wave manifolds in the weak stratification limit. Vorticity perturbations amplify in energy due to downgradient Reynolds stress when their phase lines tilt against the shear and the large growth attained is transferred to propagating gravity waves. When the flow geometry is such that the excited gravity waves are confined in the vicinity of the vorticity perturbation by their trapping levels, an overall convective collapse of this region can be anticipated. On the other hand, when the flow geometry permits wave propagation, significant gravity wave emission occurs.
Publisher
American Meteorological Society
Reference26 articles.
1. Handbook of Mathematical Functions.;Abramowwitz,1965
2. Gravity waves in a barotropic shear flow. Part I: Growth mechanisms in the absence of potential vorticity perturbations.;Bakas;J. Phys. Oceanogr.,2009
3. The emergence of coherent structures in stratified shear flow.;Bakas;J. Atmos. Sci.,2001
4. Uniform asymptotic smoothing of Stokes’s discontinuities.;Berry;Proc. Roy. Soc. London,1989
5. Generalized stability theory. Part I: Autonomous operators.;Farrell;J. Atmos. Sci.,1996
Cited by
17 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献