Baroclinic turbulence on the polar β-plane in the rotating tank: Down to submesoscale

Zhang, Y.; Afanasyev, Y. D.

doi:10.1016/j.ocemod.2016.09.013

Cited by 10 publications

(6 citation statements)

References 26 publications

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“…The 50 and 60 rpm cases clearly show spatiotemporally coherent, multiple zonal jet flow can develop in thermally‐driven laboratory experiments, thus extending the findings of, for example, Smith et al. (2014); Zhang and Afanasyev (2016); Cabanes et al. (2017); Lemasquerier et al.…”

Section: Resultssupporting

confidence: 81%

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Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments

2022

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Turbulent convection in a planet's outer core is simulated here using a thermally‐driven, free surface paraboloidal laboratory annulus. We show that the rapidly rotating convection dynamics in free‐surface paraboloidal annuli are similar those in planetary spherical shell geometries. Three experimental cases are carried out, respectively, at 35 revolutions per minute (rpm), 50 and 60 rpm. Thermal Rossby waves are detected in full disk thermographic images of the fluid's free surface. Ultrasonic flow velocity measurements reveal the presence of multiple azimuthal (zonal) jets, with successively more jets forming in higher rotation rate cases. The jets' cylindrical radial extent is well approximated by the Rhines scale. Over time, the zonal jets migrate to larger radial position with migration rates in good agreement with prior theoretical estimates. Our results suggest that planetary core rotating convection will be comprised of flow structures found in other turbulent geophysical fluid dynamical systems: convective turbulence dominates the small‐scale flow field, and also act to flux energy into larger‐scale, slowly evolving zonal flow structures. How the ambient magnetic fields in planetary core settings affect such turbulent flows remains an open question.

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Section: Resultssupporting

confidence: 81%

“…It also has similarities to the devices used to study oceanic and atmospheric flows in Matulka et al. (2016); Zhang and Afanasyev (2016, 2021) and to study atmospheric waves and mean flow dynamics in Rodda et al. (2018); Rodda et al.…”

Section: Introductionmentioning

confidence: 99%

Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments

2022

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“…The kinetic energy spectrum provides insights into the distribution of energy across different scales and is diagnostic of the flow regime. Analysis of rotating tanks with a beta plane may proceed in terms of full cylindrical polar coordinates with Bessel functions in the radial direction and Fourier modes in the azimuthal direction (e.g., Galperin, Hoemann, et al., 2014; Galperin et al., 2016; Y. Afanasyev & Wells, 2005; Zhang & Afanasyev, 2014, 2016), or alternatively, when the focus is on relatively narrow zones as in this study, a local Cartesian framework and double‐Fourier decomposition are effective (e.g., Zhang & Afanasyev, 2014, 2016). Employing the latter, denote the Fourier transform of the Cartesian velocity components as

\left(\tilde{u},\tilde{v}\right)

, and the wavenumber components as ( k x , k y ), and define

E\left({k}_{x},{k}_{y}\right)=\frac{1}{2}\left(\tilde{u}{\tilde{u}}^{\ast }+\tilde{v}{\tilde{v}}^{\ast }\right)

, where

{\tilde{u}}^{\ast }

is the complex conjugate of

\tilde{u}

.…”

Section: Resultsmentioning

confidence: 99%

Evolution of Jupiter‐Style Critical Latitudes: Initial Laboratory Altimetry Results

Afanasyev

Dowling

2022

JGR Planets

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This is a laboratory zonal‐jet study using a rotating water tank. The bottom topography has a tent‐shaped radial cross section designed to generate two critical latitudes, that is, two positions where βe, the radial gradient of the potential vorticity (PV), changes sign. This configuration is motivated by observations indicating that Jupiter and Saturn have not only multiple zonal jets, but multiple stable critical latitudes. It is known that “supersonic” critical latitudes (with respect to Rossby waves) are stable, whereas “subsonic” critical latitudes are posited to be unstable. Because Rossby waves are unidirectional, “supersonic” critical latitudes come in two varieties: Rossby Mach number MR > 1 and < 0, where the latter holds when the waves are directed downstream. Experiments focus on: (a) how do zonal jets emerge from localized forcing in a system with alternating PV gradients? and (b) what differences are there between the evolution of various types of critical latitudes? The water is forced by mass injection along one radius. Laboratory altimetry provides accurate, unobtrusive records of the circulations that reveal the emergence of counter‐propagating β‐plumes (Rossby‐wave envelopes), which expand into tank‐encircling zonal jets. The tank's negative βe zone (annulus) is characterized by MR ∼ 1. The weaker critical latitude adjusts its position by about 4% of the tank radius and maintains MR ∼ 1, similar to the state surmised for Jupiter and Saturn, whereas the stronger critical latitude vacillates while maintaining |MR| ≪ 1 and may be relevant to steep oceanic seamounts.

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“…For the first class, the directly forced zonal jets can be shear‐driven by differentially moving boundaries (e.g., Aguiar et al., 2010; Hide & Titman, 1967) or result from the conservation of angular momentum and an imposed radial flow between sources and sinks at different radii (e.g., Hide, 1968; Solomon et al., 1993; Sommeria et al., 1989; Tian et al., 2001; Weeks et al., 1997). Indirectly forced jets are the product of flow dynamics; for example, active forcing can generate and maintain an eddy field characterized by relatively small length scales, which becomes anisotropic due to the β ‐effect and cascades energy into larger‐scale zonal flows, and ultimately, an eddy‐driven zonal jet (e.g., Afanasyev & Wells, 2005; Cabanes et al., 2017; Lemasquerier et al., 2021; Matulka et al., 2016; Zhang & Afanasyev, 2016). Indirectly forced jets can also arise from the turbulence associated with small‐scale convection (e.g., Condie & Rhines, 1994; Matulka et al., 2016; Read et al., 2007; Zhang & Afanasyev, 2014), electromagnetic forcing with a conductive working fluid (e.g., Afanasyev & Wells, 2005; Afanasyev, 2019; Espa et al., 2008, 2019), or the radiation of Rossby waves by eddies via beta‐plume mechanisms (e.g., Afanasyev et al., 2011; Afanasyev & Ivanov, 2019; Zhang & Afanasyev, 2015).…”

Section: Introductionmentioning

confidence: 99%

A Laboratory Model for a Meandering Zonal Jet

Stewart

Macleod

2022

J Adv Model Earth Syst

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The meandering jet streams of the Northern Hemisphere influence the weather for more than half of Earth's population, so it is imperative that we improve our understanding of their behavior and how they respond to climate change. Here, we describe a novel laboratory model for a meandering zonal jet. This model comprises a large rotating annulus with a series of topographic ridges, and an imposed radial vorticity flux. Flow interactions with the topographic ridges operate to concentrate the zonal transport into a narrow jet, which supports the development and propagation of Rossby waves. We investigate the dynamics of the jet for a range of rotation rates, imposed radial vorticity fluxes, and topographic ridge configurations. The circulations are classified into two distinct regimes: predominantly zonal or predominantly meandering. The flow regime can be quantified by the ratio of the Ekman dissipation and jet advection timescales, which gives an indication of whether disturbances arising from the flow‐topography interaction are dissipated faster than the time taken to circuit the annulus; if not, these disturbances will reencounter the topography, and thus be reinforced and amplified. For predominantly zonal flows, the radial vorticity flux is split equally between the standing meanders and transient eddies. For predominantly meandering flows, standing meanders perform 79% of the radial vorticity flux, with 18% accommodated by the transient eddies. Our experiments indicate that the Arctic amplification associated with climate change will tend to favor predominantly zonal flow conditions, suggesting a reduced occurrence of atmospheric blocking events caused by the jet streams.

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Baroclinic turbulence on the polar β-plane in the rotating tank: Down to submesoscale

Cited by 10 publications

References 26 publications

Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments

Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments

Evolution of Jupiter‐Style Critical Latitudes: Initial Laboratory Altimetry Results

A Laboratory Model for a Meandering Zonal Jet

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