Anisotropic Lagrangian Dispersion in Rotating Flows with a β Effect

Espa, Stefania; Lacorata, Guglielmo; Nitto, Gabriella Di

doi:10.1175/jpo-d-13-045.1

Cited by 12 publications

(6 citation statements)

References 39 publications

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“…In the case of systems characterized by strong anisotropy, e.g. the polar jet stream in stratosphere, the Antarctic Circumpolar Current in the Southern Ocean or experimental flows generated in a rotating tank, the FSLE can be split into components in order to separate the contributions to the dispersion coming from along-stream and cross-stream directions 45 46 47 . The time evolution of the mean distance between two trajectories, if needed, can be reconstructed from the FSLE in the following way.…”

Section: Methodsmentioning

confidence: 99%

General characteristics of relative dispersion in the ocean

Corrado

Lacorata

Palatella

et al. 2017

Sci Rep

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The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude. This provides valuable information to undertake Lagrangian dispersion studies by means of models and/or of observational data. Moreover, our results show that the relative dispersion rates measured at submesoscale are significantly higher than for large-scale dynamics. Auxiliary analysis of high resolution GPS-tracked drifter hourly data as well as of the drogued/undrogued status of the buoys is provided in support of our conclusions. A possible application of our study, concerning reverse drifter motion and error growth analysis, is proposed relatively to the case of the missing Malaysia Airlines MH370 aircraft.

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Section: Methodsmentioning

confidence: 99%

General characteristics of relative dispersion in the ocean

Corrado

Lacorata

Palatella

et al. 2017

Sci Rep

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“…1. A detailed description of the facility is given in [39,40] where we studied anisotropic dynamic and transport processes in flows with a homogeneous forcing and their dependence on the flow parameters (i.e. the intensity of the forcing, rotation rate, etc.).…”

Section: The Experimental Setupmentioning

confidence: 99%

Anisotropic macroturbulence and diffusion associated with a westward zonal jet: From laboratory to planetary atmospheres and oceans

et al. 2016

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Turbulence with inverse energy cascade and its transport properties are investigated experimentally in a flow associated with a westward propagating jet. Turbulence and the jet were produced by an electromagnetic force in a rotating tank filled with an electrolytic saline solution. The parabolic free surface emulated the topographic β effect which evoked the zonation. The spectral and transport flow characteristics were highly anisotropic. Turbulence is diagnosed by exploring the analogy between vertical and horizontal turbulent overturns in, respectively, stably stratified and quasigeostrophic flows which gives rise to a method of potential vorticity (PV) monotonizing. The anisotropization of transport properties of the flow is investigated using the finite scale Lyapunov exponent technique. After initial exponential particle separation, radial (meridional in geophysical and planetary applications) diffusion attains a short-ranged Richardson regime which transitions to the Taylor (scale-independent diffusivity) one. The azimuthal (zonal) diffusion exhibits a double-plateau structure which attains a superdiffusive regime on large scales. The transition to the Taylor regime for the radial diffusion takes place at a scale of turbulence anisotropization. The radial eddy diffusivity in both regimes as well as the transition scale are all determined by the rate of the inverse energy cascade, ε, that can be diagnosed by the PV monotonizing. Conversely, ε can be deduced from the scale of the Richardson-Taylor regime transition in the radial eddy diffusivity which, thus, provides an additional tool of diagnosing anisotropic macroturbulence with inverse energy cascade.

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“…The anisotropy in the dispersion process can be measured computing the difference between the zonal and meridional dispersion rates at a given scale (δ), through the Lagrangian anisotropy index (LAI) defined in Espa et al (2014) as:…”

Section: Relative Dispersion Statisticsmentioning

confidence: 99%

Ageostrophic Contribution by the Wind and Waves Induced Flow to the Lateral Stirring in the Mediterranean Sea

et al. 2023

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We study the impact of the Ekman currents and Stokes drift on the surface horizontal transport and mixing properties of the Mediterranean Sea. Finite Size Lyapunov Exponents (FSLE) at the ocean surface are computed over the whole basin using 25 years of satellite altimetry derived geostrophic currents, 10‐m wind velocity and wave fields. We find that the transport pathways unveiled by the geostrophic Lagrangian Coherent Structures (LCS) are significantly modified by the ageostrophic currents (i.e., Ekman and Stokes induced velocities), often leading to a decrease of the retention capacity of the eddies. An exhaustive assessment of the regional and temporal variability of the FSLE shows an increase of the horizontal mixing processes, due to the ageostrophic component, up to 37% in regions such as the Gulf of Lion or the Aegean Sea, during the seasons where wind and waves are intense and persistent. Positive trends in the total FSLE (up to 1.2% of the value of FSLE per year in some regions) suggest that Mediterranean Sea has experienced a significant increase in the intensity of the mixing processes over the last decades. Ageostrophic features are considered to play a role in determining the properties of the relative dispersion. Through the analysis of the Lagrangian Anisotropy Index (LAI) using virtual and real pair of drifters, we observe that the particle dispersion is mainly dominated by the zonal flow, and that the ageostrophic currents induce meridional dispersion, particularly in regions where wind and wave are intensified.

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Anisotropic Lagrangian Dispersion in Rotating Flows with a β Effect

Cited by 12 publications

References 39 publications

General characteristics of relative dispersion in the ocean

General characteristics of relative dispersion in the ocean

Anisotropic macroturbulence and diffusion associated with a westward zonal jet: From laboratory to planetary atmospheres and oceans

Ageostrophic Contribution by the Wind and Waves Induced Flow to the Lateral Stirring in the Mediterranean Sea

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