scholarly journals Beta effect and slowly changing topography Rossby waves in a shear flow

2012 ◽  
Vol 61 (21) ◽  
pp. 210510
Author(s):  
Song Jian ◽  
Liu Quan-Sheng ◽  
Yang Lian-Gui
Keyword(s):  
Shear Flow ◽  
Rossby Waves ◽  
Beta Effect

Shear‐flow generation by drift/Rossby waves

1995 ◽  
Vol 2 (11) ◽  
pp. 4174-4176 ◽  
Author(s):  
P. N. Guzdar
Keyword(s):  
Shear Flow ◽  
Rossby Waves ◽  
Flow Generation

Shear-flow instability in a rotating fluid

1999 ◽  
Vol 387 ◽  
pp. 177-204 ◽  
Author(s):  
J. A. VAN DE KONIJNENBERG ◽  
A. H. NIELSEN ◽  
J. JUUL RASMUSSEN ◽  
B. STENUM
Keyword(s):  
Shear Flow ◽  
Shear Layer ◽  
Flow Instability ◽  
Experimental Situation ◽  
Point Vortex ◽  
Azimuthal Velocity ◽  
Rotating Fluid ◽  
Beta Effect ◽  
Vortex Chain ◽  
Shear Flow Instability

The instability of a forced, circular shear layer in a rotating fluid has been studied experimentally and numerically. The experiments were performed with a shallow layer of water in a parabolic tank, in which it is possible to apply radial pumping and to model a geophysical beta-effect. A shear layer was produced by a secondary rotation of the central part of the parabolic vessel. In most experiments, the shear layer takes on the appearance of a sequence of vortices, the number of which decreases with increasing strength of the shear. A beta-effect may prevent the formation of a steady vortex chain. Continuous pumping of fluid from the periphery to the centre or vice versa leads to an azimuthal velocity field corresponding to a point vortex. This azimuthal flow appears to stabilize the shear flow if it is opposite to the inner rotation, and to be destabilizing otherwise.The numerical investigations consist of the solution of the quasi-geostrophic equation in a geometry similar to the experimental situation and with a term modelling the experimental forcing. Though the numerical computations are based on a two-dimensional model, they capture the essential features of the instability and the resulting vortex structures.

scholarly journals The Compressional Beta Effect: Analytical Solution, Numerical Benchmark, and Data Analysis

2020 ◽  
Vol 77 (11) ◽  
pp. 3721-3732
Author(s):  
Hing Ong ◽  
Paul E. Roundy
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Numerical Models ◽  
Phase Speed ◽  
Static Stability ◽  
Propagation Mechanism ◽  
Vertical Wavelength ◽  
Wave Solutions ◽  
Beta Effect ◽  
Vorticity Tendency

AbstractThis study derives a complete set of equatorially confined wave solutions from an anelastic equation set with the complete Coriolis terms, which include both the vertical and meridional planetary vorticity. The propagation mechanism can change with the effective static stability. When the effective static stability reduces to neutral, buoyancy ceases, but the role of buoyancy as an eastward-propagation mechanism is replaced by the compressional beta effect (i.e., vertical density-weighted advection of the meridional planetary vorticity). For example, the Kelvin mode becomes a compressional Rossby mode. Compressional Rossby waves are meridional vorticity disturbances that propagate eastward owing to the compressional beta effect. The compressional Rossby wave solutions can serve as a benchmark to validate the implementation of the nontraditional Coriolis terms (NCTs) in numerical models; with an effectively neutral condition and initial large-scale disturbances given a half vertical wavelength spanning the troposphere on Earth, compressional Rossby waves are expected to propagate eastward at a phase speed of 0.24 m s−1. The phase speed increases with the planetary rotation rate and the vertical wavelength and also changes with the density scale height. Besides, the compressional beta effect and the meridional vorticity tendency are reconstructed using reanalysis data and regressed upon tropical precipitation filtered for the Madden–Julian oscillation (MJO). The results suggest that the compressional beta effect contributes 10.8% of the meridional vorticity tendency associated with the MJO in terms of the ratio of the minimum values.

Barotropic annular flows, vortices and waves on a beta cone

2019 ◽  
Vol 875 ◽  
pp. 225-253 ◽  
Author(s):  
Michael Rabinovich ◽  
Ziv Kizner ◽  
Glenn Flierl
Keyword(s):  
Rossby Waves ◽  
Bottom Topography ◽  
Wave Radiation ◽  
Unstable Flow ◽  
Flat Bottom ◽  
Azimuthal Mode ◽  
Initial Flow ◽  
Beta Plane ◽  
Beta Effect ◽  
Annular Flows

We consider two-dimensional quasi-geostrophic annular flows around a circular island with a radial offshore bottom slope. Since the conical bottom topography causes a certain beta effect, by analogy with the conventional beta plane we term our model a beta cone. Our focus is on the flows with zero total circulation, which are composed of two concentric rings of uniform potential vorticity (PV) attached to the island. The linear stability of such flows on a beta cone was investigated in a previous publication of ours. In the present paper, we study numerically the nonlinear evolution of weakly viscous flows, whose parameters are fitted so as to guarantee the highest instability of the azimuthal mode $m=1,\ldots ,6$. We study the production of vortices and Rossby waves due to the instability, consider the effect of waves on the emerging vortices and the interaction between the vortices. As in the flat-bottom case, at $m\geqslant 2$, the instability at weak bottom slopes normally leads to the emission of $m$ dipoles. However, a fundamental difference between the flat-bottom and beta-cone cases is observed in the trajectories of the dipoles as the latter recede from the island. When the flow is initially counterclockwise, the conical beta effect may force the dipoles to make a complete turn, come back to the island and rearrange in new couples that again leave the island and return. This quasi-periodic process gradually fades due to filamentation, wave radiation and viscous dissipation. Another possible outcome is symmetrical settling of $m$ dipoles in a circular orbit around the island, in which they move counterclockwise. This behaviour is reminiscent of the adaptation of strongly tilted beta-plane modons (dipoles) to the eastward movement. If the initial flow is clockwise, the emerged dipoles usually disintegrate, but sometimes, the orbital arrangement is possible. At a moderate slope, the evolution of an unstable flow, which is initially clockwise, may end up in the formation of a counterclockwise flow. At steeper slopes, a clockwise flow may transform into a quasi-stationary vortex multipole. When the slope is sufficiently steep, the topographic Rossby waves developing outside of the PV rings can smooth away the instability crests and troughs at the outer edge of the main flow, thus preventing the vortex production but allowing the formation of a new quasi-stationary pattern, a doubly connected coherent PV structure possessing $m$-fold symmetry. Such an $m$-fold pattern can be steady only if it rotates counterclockwise, otherwise it radiates Rossby waves and transforms eventually into a circularly symmetric flow.

On Stable and Unstable Rossby Waves in Non-Zonal Oceanic Shear Flow

1982 ◽  
Vol 12 (6) ◽  
pp. 528-537 ◽  
Author(s):  
Yong Q. Kang ◽  
James Michael Price ◽  
Lorenz Magaard
Keyword(s):  
Shear Flow ◽  
Rossby Waves

The Effects of Shear Flow on Propagation of Rossby Waves in the Equatorial Oceans

1994 ◽  
Vol 24 (7) ◽  
pp. 1680-1686 ◽  
Author(s):  
Quanan Zheng ◽  
Xiao-Hai Yan ◽  
Chung-Ru Ho ◽  
Chang-Kou Tai
Keyword(s):  
Shear Flow ◽  
Rossby Waves

scholarly journals The algebraic decay of equatorial Rossby waves in a shear flow

1987 ◽  
Vol 11 (2) ◽  
pp. 139-151 ◽  
Author(s):  
John P. Boyd ◽  
Zaphiris D. Christidis
Keyword(s):  
Shear Flow ◽  
Rossby Waves ◽  
Algebraic Decay ◽  
Equatorial Rossby Waves
Sign in / Sign up

Export Citation Format

Share Document