Piecewise uniform potential vorticity pancake shielded vortices

Reinaud, Jean Noel

doi:10.1080/03091929.2016.1275609

Cited by 6 publications

(8 citation statements)

References 41 publications

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“…We introduce a solid free-slip wall condition at the surface where the vortex intensity is maximum in order to mimic the flat ocean surface. This specific boundary condition is relevant only for surface eddies, and we exclude from the scope of our investigation intrathermocline eddies or meddies as considered by Nguyen et al (2012), Hua et al (2013), Yim et al (2016), Facchini and Le Bars (2016), Sutyrin and Radko (2017), Reinaud (2017), and Mahdinia et al (2017). Unlike these previous studies dedicated only to Gaussian lenses, we will study various radial and vertical profiles in order to extract some general stability properties which are not profile dependent.…”

Section: Introductionmentioning

confidence: 99%

Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

Yim

Stegner

Billant

2019

Journal of Physical Oceanography

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We investigate the linear stability of intense baroclinic anticyclones, with a particular focus on the centrifugal (inertial) instability. Various vertical and radial velocity profiles are studied. The vertical profiles are such that the velocity is maximum at the surface. These profiles correspond to oceanic eddies such as submesoscale mixed-layer eddies or intense mesoscale eddies in the upper thermocline. The results show that the main characteristics of the centrifugal instability (growth rate, vertical wavelength) depend weakly on the baroclinic structure of the anticyclone. The dominant azimuthal wavenumber is for small Burger number (Bu) and for higher Bu, where Bu is the square root of the ratio of the deformation radius over the characteristic eddy radius where the velocity is maximum. The marginal stability limits of the centrifugal instability for the different velocity profiles collapse approximately on a single curve in the parameter space (Ro, Bu), where is the Rossby number, with being the maximum velocity. By means of an asymptotic analysis for short vertical wavelength, an explicit prediction for the marginal stability limit is derived for a wide range of velocity profiles. We then suggest to use, for most of oceanic anticyclones, the instability criterion valid for a Gaussian eddy: where is the Ekman number, H is the eddy depth, and ν is the turbulent viscosity at the ocean surface. Some baroclinic anticyclones can remain stable even if they have a core region of negative absolute vorticity provided that they are small enough. This formula explains the few observations of intense anticyclonic eddies having a negative core vorticity around .

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Section: Introductionmentioning

confidence: 99%

Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

Yim

Stegner

Billant

2019

Journal of Physical Oceanography

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“…The second natural extension is to consider the ageostrophic effects, by studying the interaction at small yet finite Rossby number. Recent studies by Ciani et al (2016), Reinaud andDritschel (2018) andOrozco Extrada et al (2020) have shown that these effects can drastically alter the interaction between two vortices, and in particular the way they merge. Notably cyclonic and anticyclonic vortices have asymmetric dynamical behaviours.…”

Section: Discussionmentioning

confidence: 99%

“…Richardson et al 2000). The stability of various baroclinic eddies has been studied by many authors, including Nguyen et al (2012), Meunier et al (2015), Yim et al (2016), Storer et al (2018), Menesguen et al (2018), Meunier et al (2018), Carton et al (2014) for so-called Gaussian vortices, or for piecewise uniform vortices by Miyazaki et al (2003), Reinaud (2017). On the other hand, tripolar vortices where two likesigned vortices are at the same depth have been investigated by Reinaud and Carton (2015).…”

Section: Introductionmentioning

confidence: 99%

“…The merger of two monopolar planar two-dimensional vortices has been investigated by Overman II and Zabusky (1982), Melander et al (1988), Dritschel and Waugh (1992), Waugh (1992), Dritschel (1995) to name but a few studies. The merger of two monopolar three-dimensional vortices in geophysical context has been studied by von Hardenberg et al (2000), Dritschel (2002), Reinaud andDritschel (2002, 2005), Bambrey et al (2007), Ozugurlu et al (2008), Reinaud and Dritschel (2018). The upshot of these studies, and many others, is that two vortices may merge provided they are separated by a distance less than a threshold known as the critical merger distance.…”

Section: Introductionmentioning

confidence: 99%

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The merger of two three-dimensional quasi-geostrophic baroclinic tripolar eddies

Reinaud

Carton

2021

Geophysical & Astrophysical Fluid Dynamics

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We investigate the strong interaction between two baroclinic tripolar eddies in a three-dimensional, rapidlyrotating, continuously stratified flow under the quasi-geostrophic approximation. Each tripolar eddy consists of an anticyclonic central vortex with two oblate cyclonic vortices located above and below the anticyclone. The interaction depends on the vertical and horizontal offsets between the two tripolar eddies. For small and low PV oblate cyclones, each tripolar eddy alone is only weakly unstable to a baroclinic mode. The instability puts the three vortices out of alignment. Most of the eddy however survives the instability. When two tripolar eddies interact, their constituent vortices may merge. Merger occurs when the eddies are close enough together, and shows similarities with the merger of monopolar vortices. Vertically separated eddies do not align vertically. This suggests the importance of an external flow for the alignment, observed in the oceans, to occur. We finally show that the interaction between two tripolar eddies with intense oblate cyclones is very different and show similarities with the dynamics of dipolar baroclinic eddies known as hetons.

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“…The Journal of Geophysical Research: Oceans 10.1002/2017JC013610 shielded eddy has a core of vorticity of one sign surrounded (or shielded) by a layer of smaller eddies of opposite-signed vorticity. This type of vortex has been studied in a theoretical and idealized setup (see e.g., Carton, 1992;Flierl, 1988;Reinaud, 2017). The discovery of shielded eddies in the real ocean is a result deserving special consideration.…”

Section: Comparison Of Hydrographic Cross Sections During May 2004mentioning

confidence: 99%

How Eddies Gain, Retain, and Release Water: A Case Study of a Hokkaido Anticyclone

2018

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A Lagrangian methodology is elaborated to identify the origin of water masses in the Kuroshio‐Oyashio frontal zone where waters of the Kuroshio Extension and Oyashio Current and of the Japan and Okhotsk Seas converge. It allows one to track the evolution of mesoscale eddies during the satellite‐altimetry era and to document how they gain, retain, and release water masses of different origin. The methodology is applied to study warm‐core mesoscale anticyclones propagating along the Japan and Kuril Trenches near the eastern coast of Hokkaido Island that have been observed from 1 January 1993 to 10 December 2016 in an altimetry‐based velocity field. The Hokkaido eddy, sampled by profiling floats and a few cruises in 2003 and 2004, is analyzed in detail in order to compare Lagrangian simulation results to observations.

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Piecewise uniform potential vorticity pancake shielded vortices

Cited by 6 publications

References 41 publications

Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

The merger of two three-dimensional quasi-geostrophic baroclinic tripolar eddies

How Eddies Gain, Retain, and Release Water: A Case Study of a Hokkaido Anticyclone

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