Geostrophic vortex dynamics

Polvani, Lorenzo M.

doi:10.1575/1912/4961

Cited by 28 publications

(26 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For these large vortices or eddies, the dominance of the barotropic mode implies the topographic interaction resembles the first example; however, the steady propagating states with overlapping upper and lower layer PV patches (Polvani, 1988) tend not to be stable. For vortices (R≥3R d ), the anticyclone splits along the topography such that part is left along the slope (Fig.…”

Section: An F -Plane Heton-like Dipolementioning

confidence: 99%

“…The black contour centered along the escarpment at the initial time is the boundary of the high PV fluid that originates on the shallow region. As the eddies advect one another shoreward they become more elongated because of the strain fields from the opposite member of the pair; we could have avoided this by starting with the dipole "V-state" (Wu et al, 1984;Polvani, 1988) in which vortices are elongated initially, but would not expect the topographic interactions to be significantly different.…”

Section: Barotropic Dipolementioning

confidence: 99%

See 1 more Smart Citation

Transformation of an Agulhas eddy near the continental slope

et al. 2010

View full text Add to dashboard Cite

Abstract. The transformation of Agulhas eddies near the continental slope of southern Africa and their subsequent self-propagation are analyzed in both observational data and numerical simulations. Self-propagation results from a net dipole moment of a generalized heton structure consisting of a surface-intensified anticyclonic eddy and deep cyclonic pattern. Such Agulhas vortical structures can form near the retroflection region and further north along the western coast of southern Africa. We analyze nonlinear topographic wave generation, vortex deformations, and filament production as an important part in water mass exchange. Self-propagating structures provide a conduit for exchange between the deep ocean and shelf regions in the Benguela upwelling system.

show abstract

Section: An F -Plane Heton-like Dipolementioning

confidence: 99%

Section: Barotropic Dipolementioning

confidence: 99%

Transformation of an Agulhas eddy near the continental slope

et al. 2010

View full text Add to dashboard Cite

show abstract

“…In two-dimensions, among the various types of fundamental interactions between vortices, it is the question of the merger of two regions of same-sign vorticity that has alignment process has been studied in detail (Polvani 1988), and will be the subject of a second paper.…”

Section: Introductionmentioning

confidence: 99%

Two-layer geostrophic vortex dynamics. Part 2. Alignment and two-layer V-states

Polvani

1991

J. Fluid Mech.

106

View full text Add to dashboard Cite

We generalize the methods of two-dimensional contour dynamics to study a twolayer rotating fluid that obeys the quasi-geostrophic equations. We consider here only the case of a constant-potential-vorticity lower layer. We derive equilibrium solutions for monopolar (rotating) and dipolar (translating) geostrophic vortices in the upper layer, and compare them with the Euler case. We show that the equivalent barotropic (infinite lower layer) case is a singular limit of the two-layer system. We also investigate the effect of a finite lower layer on the merger of two regions of equalsign potential vorticity in the upper layer. We discuss our results in the light of the recent laboratory experiments of Griffiths & Hopfinger (1986). The process of filamentation is found to be greatly suppressed for equivalent barotropic dynamics on scales larger than the radius of deformation. We show that the variation of the critical initial distance for merger as a function of the radius of deformation and the ratio of the layers at rest is closely related to the existence of vortex-pair equilibria and their geometrical properties.

show abstract

“…In particular, the two-layer quasi-geostrophic potential vorticity equations can where R = [(X -zI) 2 + (y -y') 2 11/ 2 and G; 3 is the Green's function for the effect in layer i of a point vortex in layer j (Polvani, 1988). For this problem, a subset of the Gi,'s is needed since the vorticity is zero everywhere except within the region of fluid that originated over the topography in the lower layer.…”

Section: Methodsmentioning

confidence: 99%

“…Before showing how contour dynamics can be used in the study of flow over topography, we first describe the technique in general. This technique has been used previously in the study of vortex dynamics ( Polvani, 1988;and Zabusky et. al., 1979).…”

Section: Flow In One Layer Over Small Topographymentioning

confidence: 99%

Flow over finite isolated topography

Thompson¹

1990

View full text Add to dashboard Cite

One and two layer models are used to study flow over axisymmetric isolated topography. Inviscid or nearly inviscid flow in which non-linear effects have order one importance is considered, and both the effects of P and finite topography are included.A one-layer quasi-geostrophic model is used to find the shape of Taylor columns on both the f-plane and the #-plane in the inviscid limit of the frictional problem.In this limit, the boundary of the Taylor column is a streamline, and the velocity in both directions vanishes on the boundary. The fluid within the Taylor column is stagnant, corresponding to the solution that Ingersoll (1969) found for flow over a right circular cylinder on the f-plane. In this case, the Taylor column is circular. An iterative boundary integral technique is used to find the solutions for flow over a cone on the f-plane. In this case the Taylor column has a tear drop shape. Solutions are also found for flow on the #-plane over a cylinder, and the Taylor column is approximately elliptical for westward flow with the major axis in the x direction, while it is slightly elongated in the y direction for eastward flow. The stagnation point of the Taylor column is located on the edge of the topography for all the solutions found. It was not possible to find solutions for smooth topographic shapes. Steady solutions for flow over a right circular cylinder of finite height are studied when the quasi-geostrophic approximation no longer applies. The solution consists of two parts, one which is similar to the quasi-geostrophic solution and is driven by the potential vorticity anomaly over the topography and the other which is similar to the solution of potential flow around an cylinder and is driven by the matching conditions on the edge of the topography. When the effect of # is large, the transport over the topography is enhanced as the streamlines follow lines of constant background potential vorticity. For eastward flow, the Rossby wave drag can be much larger than predicted from quasi-geostrophic theory.A two-layer model over finite topography using the quasi-geostrophic approximation is developed. The topography is a right circular cylinder which goes all of the way through the lower layer and an order Rossby number amount into the upper layer, so that the quasi-geostrophic approximation can be applied consistently. This geometry allows description of flow in which an isopycnal intersects the topography. The model is valid for a different regime than existing models of steady flow over finite topography in a continuously stratified fluid in which the bottom boundary is an isopycnal surface. The solutions contain the two components that are found in the the barotropic model of flow over finite topography. The model breaks down when the interface goes above the topography which occurs more easily when the stratification is weak. Closed streamlines occur more readily over the topography when the stratification is weak, whereas in traditional quasi-geostrophic theory they occur more readily w...

show abstract

Geostrophic vortex dynamics

Cited by 28 publications

References 50 publications

Transformation of an Agulhas eddy near the continental slope

Transformation of an Agulhas eddy near the continental slope

Two-layer geostrophic vortex dynamics. Part 2. Alignment and two-layer V-states

Flow over finite isolated topography

Contact Info

Product

Resources

About