Quasi-two-dimensional flow on the polar β-plane: Laboratory experiments

Espa, Stefania; Cenedese, A.; Mariani, M.; Carnevale, G. F.

doi:10.1016/j.jmarsys.2008.10.015

Cited by 10 publications

(8 citation statements)

References 16 publications

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“…3-b). Similar results have been found in Espa et al [3,35] and in [36] in which the authors studied also the asymmetry between cyclonic/anticyclonic vortices. EM forcing in a forced regime was used in Espa et al [4] in order to study small-scale turbulence on the β-plane in a more realistic configuration, since in nature the energy is continuously supplied.…”

Section: The β-Plane Turbulencesupporting

confidence: 90%

“…In the first reported experiments of this kind, it was found that the induced fluid velocity was proportional to the magnitude of the EM forcing [34]. EM forcing was used also to study β-plane turbulence in decaying [2,3,35,36] and forced regimes [4]. In this paper we will show results from experiments performed in a rotating electromagnetic cell.…”

Section: The β-Plane Turbulencementioning

confidence: 97%

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Zonal Jets in Rotating Shallow Water Turbulence

Nitto

Espa

Cenedese

2013

EARTH

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During the last three decades, the appearance of multiple zonal jets in planetary atmospheres and in the Earth's oceans has widely studied. Evidences of this phenomenon were recovered in numerical simulations [1], laboratory experiments [2][3][4] and in field measurements of giant planets' atmosphere [5]. Recent studies have revealed the presence of zonation also in the Earth's oceans; in fact, zonal jets were recovered in the outputs of Oceanic General Circulation Models-GCMs [6] and from satellite altimetry observations [7]. In previous works [3-4], we have investigated the impact of several experimental parameters on jets organization both in decaying and forced regimes. This work shows new results in the context of continuously forced flows obtained performing experiments in a bigger domain. The experimental set-up consists of a rotating tank where the initial distribution of vorticity is generated via the Lorentz force in an electromagnetic cell and the latitudinal variation of the Coriolis parameter is simulated by the parabolic profile assumed by the free surface of the rotating fluid. The velocity fields were measured using an image analysis technique. The flow is characterized in terms of zonal and radial flow pattern, flow variability and jet scales.

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Section: The β-Plane Turbulencesupporting

confidence: 90%

Section: The β-Plane Turbulencementioning

confidence: 97%

Zonal Jets in Rotating Shallow Water Turbulence

Nitto

Espa

Cenedese

2013

EARTH

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“…In future work, we plan experiments with much larger mean depth, a much smaller variation of depth variation to mean depth and smaller Rossby numbers [21]. The QG simulations may then be expected to provide a closer match to those experiments.…”

Section: Discussionmentioning

confidence: 94%

“…The β effect may also be enhanced by adding a bottom topography to the same configuration; in this case to evaluate the effective β, the gradient of the total depth at r m has to be evaluated [21].…”

Section: The Modelmentioning

confidence: 99%

Quasi-two-dimensional decaying turbulence subject to the β effect

Espa¹,

Carnevale

Cenedese³

et al. 2008

Journal of Turbulence

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Freely decaying quasi-2D turbulence under the influence of a meridional variation of the Coriolis parameter f (β effect) is experimentally and numerically modelled. The experimental flow is generated in a rotating electromagnetic cell where the variation of f is approximated by a nearly equivalent topographical effect. In the presence of a high β effect, the initial disordered vorticity field evolves to form a weak polar anticyclonic circulation surrounded by a cyclonic zonal jet demonstrating the preferential transfer of energy towards zonal motions. In agreement with theoretical predictions, the energy spectrum becomes peaked near the Rhines wave number with a steep fall-off beyond, indicating the presence of a soft barrier to the energy transfer towards larger scales. DNS substantially confirmed the experimental observations.

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“…The parabolic free surface assumed by the fluid under rotation is used to model the β ‐effect in laboratory [ Afanasyev and Wells , 2005; Espa et al , 2008], in our model the point of maximum depression of the fluid surface represents the pole while the peripheral areas of the domain correspond to lower latitudes. The corresponding expression for β can be found in Espa et al [2009]. The experiments are characterized by different values of the fluid depth, the rotation rate of the table, and the forcing intensity in terms of the input current I , see Table 1.…”

Section: Laboratory Experimentsmentioning

confidence: 99%

On the influence of a β‐effect on Lagrangian diffusion

Lacorata

Espa

2012

Geophysical Research Letters

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[1] Geophysical turbulence is strongly influenced by the variation of the Coriolis force with latitude (b-effect): when this effect is significant an anisotropic inverse cascade is developed since energy is preferentially transferred towards zonal modes. The consequent emergence of flow structures along the zonal direction can strongly impact turbulent transport and modify meridional scalar diffusion. In this letter we investigate zonal and meridional diffusion in laboratory experiments of turbulence affected by a b-effect. The degree of anisotropy and the flow characteristic scales have been quantified according to a Lagrangian approach based on the reconstruction of tracer trajectories, i.e., in analogy with oceanic drifters data, and on the Finite-Scale Lyapunov Exponent (FSLE) analysis. An experimental confirmation of a recently introduced scaling law for the meridional diffusion in the marginally zonostrophic regime is also presented. Turbulence and Diffusion in Flows With a b-Effect[2] Large scale planetary and terrestrial circulation are studied under the paradigm of the geostrophic turbulence introduced by Charney [1971] to model a turbulent, rotating, stably stratified fluid in near geostrophic balance. This model, based on the three-dimensional inviscid conservation equation for the potential vorticity, presents several analogies with purely 2D turbulence, e.g., the conservation of two quadratic invariants. Nevertheless, important differences exist [Read, 2001]. Here, among these differences, we will focus on turbulence modification by the meridional variation of the Coriolis parameter, i.e., the so-called b-effect, defined approximately as f = f 0 + by, where f 0 is twice the rotation angular velocity W and y is the latitude coordinate. Rhines considered this problem in the context of unforced barotropic flows [Rhines, 1975] demonstrating that the b-effect induces the anisotropization of the upward energy transfer preferentially directing it towards zonal modes. The emergence of the flow anisotropy was explained in terms of a competition between nonlinear and b terms and anisotropy of the dispersion relation. The associated characteristic scale separating the regions of wave vector space where either b or nonlinear effects respectively dominate is known as the Rhines wavenumber, n R , and can be expressed in terms of the root mean square of the velocity and b. Similar ideas can be applied to geostrophic turbulence where the baroclinic instability takes the role of the small-scale forcing and the non-linear interaction between eddies and the mean flow plays an important role in flow anisotropization; nevertheless, for small Burger numbers, the inverse cascade develops in the barotropic mode due to the barotropization mechanism [Salmon, 1980;Rhines, 1994;Read, 2001;Galperin et al., 2010].[3] The concept of the cascade arrest was introduced by Rhines [1975] for unforced flows and recently revisited by Sukoriansky et al. [2007] in the context of small-scale forced, large-scale damped, barotropic vorticit...

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Quasi-two-dimensional flow on the polar β-plane: Laboratory experiments

Cited by 10 publications

References 16 publications

Zonal Jets in Rotating Shallow Water Turbulence

Zonal Jets in Rotating Shallow Water Turbulence

Quasi-two-dimensional decaying turbulence subject to the β effect

On the influence of a β‐effect on Lagrangian diffusion

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