Instability and Splitting of Mesoscale Rings using a Two-Layer Quasi-Geostrophic Model on an<i>f</i>-Plane

Ikeda, Motoyoshi

doi:10.1175/1520-0485(1981)011<0987:iasomr>2.0.co;2

Cited by 60 publications

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“…A small surfacetrapped potential vortex remains behind, at center, so three surface vortices have been produced by the instability. In general the evolution here closely resembles that in figures (7-8) of Ikeda (1981) and figure 6 of Helfrich and Send (1988).…”

Section: Two-layer Results: a Surface Vortexsupporting

confidence: 82%

“…In the intermediate cases, the surface vortex is deformed by the initial perturbation, but relaxes thereafter toward axisymmetry (much like a sub critical case considered in Ikeda, 1981). The return to the initial scale of the surface PV is seen in particular in the A = .72 case.…”

Section: Two-layer Results: a Surface Vortexmentioning

confidence: 82%

“…The stability of a baroclinic vortex has been studied previously in the laboratory by Saunders (1973) and Griffths and Linden (1981), and theoretically by Ikeda (1981), Pedlosky (1985), Flierl (1988) and Helfrich and Send (1988). The general picture which emerges is that vortices which are suffciently larger than deformation scale and in which the barotropic circulation is not overly strong are baroclinically unstable.…”

Section: Two-layer Results: a Surface Vortexmentioning

confidence: 99%

“…The most unstable azimuthal mode increases with vortex scale. In the finite amplitude state, the larger vortices may break into separating baroclinic dipoles (Ikeda, 1981;Helfrich and Send, 1988) of the sort categorized by Flierl et aL. (1980), finite-area versions of the "hetons" of Hogg and Stommel (1985).…”

Section: Two-layer Results: a Surface Vortexmentioning

confidence: 99%

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Baroclinic vortices over a sloping bottom

LaCasce¹

1996

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Section: Two-layer Results: a Surface Vortexsupporting

confidence: 82%

Section: Two-layer Results: a Surface Vortexmentioning

confidence: 82%

Section: Two-layer Results: a Surface Vortexmentioning

confidence: 99%

Section: Two-layer Results: a Surface Vortexmentioning

confidence: 99%

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Baroclinic vortices over a sloping bottom

LaCasce¹

1996

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“…2,6,[7][8][9][10] Our full nonlinear simulations of distorted axisymmetric monopoles suggest that sheardiffusion mixing governs the relaxation toward the tripole attractor for a moderate perturbation just as it would toward the monopole attractor for slight perturbations. In the case of the tripole, the positive portion of the quadrupolar disturbance is thoroughly mixed, while the negative portion persists to form a quasi-steady rotating tripole.…”

Section: Introductionmentioning

confidence: 79%

Quasi-steady monopole and tripole attractors for relaxing vortices

1997

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Using fully nonlinear simulations of the two-dimensional Navier-Stokes equations at large Reynolds number ͑Re͒, we bracket a threshold amplitude above which a perturbed Gaussian monopole will relax to a quasi-steady, rotating tripole, and below which will relax to an axisymmetric monopole. The resulting quasi-steady structures are robust to small perturbations. We propose a means of measuring the decay rate of disturbances to asymptotic vortical structures wherein streamlines and lines of constant vorticity correspond in some rotating or translating frame. These experiments support the hypothesis that small or moderate deviations from asymptotic structures decay through inviscid and viscous mixing.

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Why compensated cold‐core rings look stable

Sutyrin

2015

Geophysical Research Letters

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In contrast to many real‐ocean rings and eddies, circular vortices in idealized two‐layer models tend to be highly unstable, unless their radius is made small or their baroclinicity is made artificially weak. The addition of a middle layer with uniform potential vorticity weakens vertical coupling between the upper and lower layers that enhances vortex stability and makes the vortex lifespan more realistic. It is demonstrated here that such a three‐layer vortex model in so‐called compensated state (without rotation in the deep layer) possesses smaller lower interface slope than the two‐layer model that reduces the potential vorticity gradient in the lower layer and provides less unstable configurations. Numerical simulations of an unstable cyclone with parameters typical for cold‐core ring Bob reveal strong deformations and pulsations of the vortex core in the two‐layer setup, while the ring becomes only slightly deformed and looks stable when the middle layer with uniform potential vorticity is added to be consistent with observations. Enhanced vortex stability in such three‐layer setup has important implications for further studies of real‐ocean eddies.

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Instability and Splitting of Mesoscale Rings using a Two-Layer Quasi-Geostrophic Model on anf-Plane

Cited by 60 publications

References 0 publications

Baroclinic vortices over a sloping bottom

Baroclinic vortices over a sloping bottom

Quasi-steady monopole and tripole attractors for relaxing vortices

Why compensated cold‐core rings look stable

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