Special Issue "Lagrangian Transport in Geophysical Fluid Flows"

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: 20 November 2020.

Special Issue Editors

Dr. Irina Rypina
Website SciProfiles
Guest Editor
Physical Oceanography Department, Woods Hole Oceanographic Institution, 266 Woods Hole Rd., Woods Hole, MA 02543, USA
Interests: transport and exchange processes in oceanic and atmospheric flows; effects of transport processes on redistribution of physical, chemical, and biological tracers in the ocean and atmosphere; Lagrangian approach to studying transport; ocean and atmosphere dynamics; dynamical systems theory; Hamiltonian dynamics
Dr. Michael Allshouse
Website SciProfiles
Guest Editor
Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA
Interests: nonlinear dynamics; geophysical fluid dynamics; computational fluid mechanics; disaster response; experimental fluids

Special Issue Information

Dear Colleagues,

Many questions in oceanography, meteorology, and related disciplines involve, in an unavoidable way, transport—transport of mass, properties, biogeochemical tracers, pollutants, or biological organisms. A Lagrangian perspective, where one tracks individual parcels, presents a natural framework for characterizing transport pathways, barriers, and associated exchanges. The aim of this Special Issue is to assemble a variety of articles to develop a deeper understanding of the Lagrangian transport and exchange processes in geophysical fluid flows. We welcome all contributions, ranging from theoretical advancements to numerical modeling and analysis of observational datasets; from idealized problems to realistic flows; and from submeso-scales to global scales.

Dr. Irina Rypina
Dr. Michael Allshouse
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Lagrangian transport
  • exchange processes
  • geophysical fluid flows
  • oceanic flows
  • atmospheric flows

Published Papers (5 papers)

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Research

Open AccessArticle
Uncertainty Quantification of Trajectory Clustering Applied to Ocean Ensemble Forecasts
Fluids 2020, 5(4), 184; https://doi.org/10.3390/fluids5040184 - 17 Oct 2020
Abstract
Partitioning ocean flows into regions dynamically distinct from their surroundings based on material transport can assist search-and-rescue planning by reducing the search domain. The spectral clustering method partitions the domain by identifying fluid particle trajectories that are similar. The partitioning validity depends on [...] Read more.
Partitioning ocean flows into regions dynamically distinct from their surroundings based on material transport can assist search-and-rescue planning by reducing the search domain. The spectral clustering method partitions the domain by identifying fluid particle trajectories that are similar. The partitioning validity depends on the accuracy of the ocean forecasting, which is subject to several sources of uncertainty: model initialization, limited knowledge of the physical processes, boundary conditions, and forcing terms. Instead of a single model output, multiple realizations are produced spanning a range of potential outcomes, and trajectory clustering is used to identify robust features and quantify the uncertainty of the ensemble-averaged results. First, ensemble statistics are used to investigate the cluster sensitivity to the spectral clustering method free-parameters and the forecast parameters for the analytic Bickley jet, a geostrophic flow model. Then, we analyze an operational coastal ocean ensemble forecast and compare the clustering results to drifter trajectories south of Martha’s Vineyard. This approach identifies regions of low uncertainty where drifters released within a cluster predominantly remain there throughout the window of analysis. Drifters released in regions of high uncertainty tend to either enter neighboring clusters or deviate from all predicted outcomes. Full article
(This article belongs to the Special Issue Lagrangian Transport in Geophysical Fluid Flows)
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Open AccessArticle
Cross-Shelf Transport Through the Interaction among a Coastal Jet, a Topographic Wave, and Tides
Fluids 2020, 5(4), 181; https://doi.org/10.3390/fluids5040181 - 16 Oct 2020
Abstract
Shelf break flows are often characterized by along-isobath jets with cross-shelf currents associated with tides and waves guided by variable topography. Here, we address the question: Can a superposition of such flows produce significant aperiodic cross-shelf transport? To answer this question, we use [...] Read more.
Shelf break flows are often characterized by along-isobath jets with cross-shelf currents associated with tides and waves guided by variable topography. Here, we address the question: Can a superposition of such flows produce significant aperiodic cross-shelf transport? To answer this question, we use a barotropic analytic model for the jet based on a similarity solution of the shallow water equations over variable topography, a wave disturbance determined by the topography, and a diurnal tidal disturbance. We use standard Lagrangian methods to assess the cross-shelf transport, presenting the results, however, in a Eulerian frame, so as to be amenable to oceanographic observations. The relative roles of the different flow components in cross-shelf transport are assessed through an extensive parameter study. We find that a superposition of all three flow components can indeed produce consequential background aperiodic transport. An application of the model using recent observations from the Texas Shelf demonstrates that a combination of these background mechanisms can produce significant transport under realistic conditions. Full article
(This article belongs to the Special Issue Lagrangian Transport in Geophysical Fluid Flows)
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Open AccessArticle
Investigating the Formation of Submesoscale Structures along Mesoscale Fronts and Estimating Kinematic Quantities Using Lagrangian Drifters
Fluids 2020, 5(3), 159; https://doi.org/10.3390/fluids5030159 - 14 Sep 2020
Abstract
Much of the vertical transport near the surface of the ocean, which plays a critical role in the transport of dissolved nutrients and gases, is thought to be associated with ageostrophic submesoscale phenomena. Vertical velocities are challenging not only to model accurately, but [...] Read more.
Much of the vertical transport near the surface of the ocean, which plays a critical role in the transport of dissolved nutrients and gases, is thought to be associated with ageostrophic submesoscale phenomena. Vertical velocities are challenging not only to model accurately, but also to measure because of how difficult they are to locate in the surface waters of the ocean. Using unique massive drifter releases during the Lagrangian Submesoscale Experiment (LASER) campaign in the Gulf of Mexico and the Coherent Lagrangian Pathways from the Surface Ocean to the Interior (CALYPSO) experiment in the Mediterranean Sea, we investigate the generation of submesoscale structures along two different mesoscale fronts. We use a novel method to project Lagrangian trajectories to Eulerian velocity fields, in order to calculate horizontal velocity gradients at the surface, which are used as a proxy for vertical transport. The velocity reconstruction uses a squared-exponential covariance function, which characterizes velocity correlations in horizontal space and time, and determines the scales of variation using the data itself. SST and towed CTD measurements support the findings revealed by the drifter data. Due to the production of a submesoscale instability eddy in the Gulf of Mexico, convergence magnitudes of up to ∼20 times the planetary vorticity, f, are observed, the value of which is almost 3 times larger than that found in the mesoscale dominated Western Mediterranean Sea. Full article
(This article belongs to the Special Issue Lagrangian Transport in Geophysical Fluid Flows)
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Open AccessArticle
Lagrangian Statistics of Heat Transfer in Homogeneous Turbulence Driven by Boussinesq Convection
Fluids 2020, 5(3), 127; https://doi.org/10.3390/fluids5030127 - 03 Aug 2020
Abstract
The movement of heat in a convecting system is typically described by the nondimensional Nusselt number, which involves an average over both space and time. In direct numerical simulations of turbulent flows, there is considerable variation in the contributions to the Nusselt number, [...] Read more.
The movement of heat in a convecting system is typically described by the nondimensional Nusselt number, which involves an average over both space and time. In direct numerical simulations of turbulent flows, there is considerable variation in the contributions to the Nusselt number, both because of local spatial variations due to plumes and because of intermittency in time. We develop a statistical approach to more completely describe the structure of heat transfer, using an exit-distance extracted from Lagrangian tracer particles, which we call the Lagrangian heat structure. In a comparison between simulations of homogeneous turbulence driven by Boussinesq convection, the Lagrangian heat structure reveals significant non-Gaussian character, as well as a clear trend with Prandtl number and Rayleigh number. This has encouraging implications for simulations performed with the goal of understanding turbulent convection in natural settings such as Earth’s atmosphere and oceans, as well as planetary and stellar dynamos. Full article
(This article belongs to the Special Issue Lagrangian Transport in Geophysical Fluid Flows)
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Open AccessArticle
Role of Surface-Layer Coherent Eddies in Potential Vorticity Transport in Quasigeostrophic Turbulence Driven by Eastward Shear
Fluids 2020, 5(1), 2; https://doi.org/10.3390/fluids5010002 - 22 Dec 2019
Abstract
The transport by materially coherent surface-layer eddies was studied in a two-layer quasigeostrophic model driven by eastward mean shear. The coherent eddies were identified by closed contours of the Lagrangian-averaged vorticity deviation obtained from Lagrangian particles advected by the flow. Attention was restricted [...] Read more.
The transport by materially coherent surface-layer eddies was studied in a two-layer quasigeostrophic model driven by eastward mean shear. The coherent eddies were identified by closed contours of the Lagrangian-averaged vorticity deviation obtained from Lagrangian particles advected by the flow. Attention was restricted to eastward mean flows, but a wide range of flow regimes with different bottom friction strengths, layer thickness ratios, and background potential vorticity (PV) gradients were otherwise considered. It was found that coherent eddies become more prevalent and longer-lasting as the strength of bottom drag increases and the stratification becomes more surface-intensified. The number of coherent eddies is minimal when the shear-induced PV gradient is 10–20 times the planetary PV gradient and increases for both larger and smaller values of the planetary PV gradient. These coherent eddies, with an average core radius close to the deformation radius, propagate meridionally with a preference for cyclones to propagate poleward and anticyclones to propagate equatorward. The meridional propagation preference of the coherent eddies gives rise to a systematic upgradient PV transport, which is in the opposite direction as the background PV transport and not captured by standard Lagrangian diffusivity estimates. The upgradient PV transport by coherent eddy cores is less than 15% of the total PV transport, but the PV transport by the periphery flow induced by the PV inside coherent eddies is significant and downgradient. These results clarify the distinct roles of the trapping and stirring effect of coherent eddies in PV transport in geophysical turbulence. Full article
(This article belongs to the Special Issue Lagrangian Transport in Geophysical Fluid Flows)
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