References of "Deleersnijder, Eric"
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See detailResidence time vs influence time
Delhez, Eric ULg; de Brye, Bejamin; de Brauwere, Anouk et al

in Journal of Marine Systems (2014), 132

The concepts of age, residence time, exposure time and influence time provide space and time dependent quantitative measures of the rate at which watermasses and pollutants enter and/or leave a control ... [more ▼]

The concepts of age, residence time, exposure time and influence time provide space and time dependent quantitative measures of the rate at which watermasses and pollutants enter and/or leave a control domain. To help avoid confusion between these concepts, this paper provides clear definitions of the residence time and the influence time. The similarities and differences between them are illustrated using both a simplified 1D advection–diffusion model and a realistic two-dimensional model of the Scheldt Estuary (Belgium and the Netherlands). The residence time of a water parcel in a control domain is the time taken by this parcel to leave the control domain for the first time. The influence time is the time required to replace the water in the domain of interest by renewing water. For steady flows, the influence time is numerically identical to the age of the renewing water, but the two timescales differ for unsteady flows. The residence timemeasures the influence of a hypothetical point discharge on a control domain. In environmental studies, it provides a measure of the effectiveness of hydrodynamic processes at helping a semi-enclosed basin to recover froma local pollution event. The influence time quantifies the local influence of a tracer that would be uniformly distributed in the control domain at the initial time. It is therefore a relevant diagnostic tool in impact studies focusing on the local persistence of a pollution problem. [less ▲]

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See detailResidence and exposure times : when diffusion does not matter
Delhez, Eric ULg; Deleersnijder, Eric

in Ocean Dynamics (2012), 62

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See detailThe leaky funnel model revisited
Mouchet, Anne ULg; Deleersnijder, Eric; Primeau, François

in Tellus : Series A (2012), 64

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See detailWater renewal timescales in the Scheldt Estuary
de Brye, Benjamin; de Brauwere, Anouk; Gourgue, Olivier et al

in Journal of Marine Systems (2012), 94

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See detailAssessing the World Ocean ventilation timescales with simple analogs - the leaky funnel model
Mouchet, Anne ULg; Deleersnijder, Eric

Poster (2011, May)

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See detailCHOLTIC Epidémies de choléra au lac Tanganyika induites par les changements climatiques ?
Plisnier, Pierre-Denis; Bompangue, Didier; Piarroux, Renaud et al

in Sciences Connection (2011), 35(Juillet-Août), 38-42

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See detailAbsorbing layers for shallow water models
Modave, Axel ULg; Deleersnijder, Eric; Delhez, Eric ULg

Conference (2010, May 11)

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See detailOn the parameters of absorbing layers for shallow water models
Modave, Axel ULg; Deleersnijder, Eric; Delhez, Eric ULg

in Ocean Dynamics (2010), 60(1), 65-79

Absorbing/sponge layers used as boundary conditions for ocean/marine models are examined in the context of the shallow water equations with the aim to minimize the reflection of outgoing waves at the ... [more ▼]

Absorbing/sponge layers used as boundary conditions for ocean/marine models are examined in the context of the shallow water equations with the aim to minimize the reflection of outgoing waves at the boundary of the computationaldomain. The ptimization of the absorption coefficient is not an issue in continuous models, for the reflection coefficient of outgoing waves can then be made as small as we please by increasing the absorption coefficient. The optimization of the parameters of absorbing layers is therefore a purely discrete problem. A balance must be found between the efficient damping of outgoing waves and the limited spatial resolution with which the resulting spatial gradients must be described. Using a one-dimensional model as a test case, the performances of various spatial distributions of the absorption coefficient are compared. Two shifted hyperbolic distributions of the absorption coefficient are derived from theoretical considerations for a pure propagative and a pure advective problems. These distribution show good performances. Their free parameter has a well-defined interpretation and can therefore be determined on a physical basis. The properties of the two shifted hyperbolas are illustrated using the classical two-dimensional problems of the collapse of a Gaussianshaped mound of water and of its advection by a mean current. The good behavior of the resulting boundary scheme remains when a full non-linear dynamics is taken into account. [less ▲]

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See detailAn Improved Methodology for Filling Missing Values in Spatiotemporal Climate Dataset: Application to Tanganyika Lake Dataset
Sorjamaa, Antti; Lendasse, Amaury; Cornet, Yves ULg et al

in Computational Geosciences (2010), 14(1), 55-64

In this paper, an improved methodology for the determination of missing values in a spatio-temporal database is presented. This methodology performs denoising projection in order to accurately fill the ... [more ▼]

In this paper, an improved methodology for the determination of missing values in a spatio-temporal database is presented. This methodology performs denoising projection in order to accurately fill the missing values in the database. The improved methodology is called EOF Pruning and it is based on an original linear projection method called Empirical Orthogo- nal Functions (EOF). The experiments demonstrate the performance of the improved methodology and present a comparison with the original EOF and with a widely-used Optimal Interpolation method called Objective Analysis. [less ▲]

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See detailCapturing the residence time boundary layer - Application to the Scheldt Estuary.
Blaise, Sébastien; de Brye, Benjamin; de Brauwere, Anouk et al

in Ocean Dynamics (2010), 60(3), 535-554

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See detailResidence time and exposure time of sinking phytoplankton in the euphotic layer
Delhez, Eric ULg; Deleersnijder, Eric

in Journal of Theoretical Biology (2010), 262

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See detailAssessing the World Ocean ventilation timescales with simple analogs - the leaky funnel model
Mouchet, Anne ULg; Deleersnijder, Eric

Conference (2009, February)

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See detailEcological modeling of the upper layers of Lake Kivu: a progress report
Leblanc, Christophe; Darchambeau, François ULg; Descy, Jean-Pierre et al

Conference (2009, January 19)

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See detailLimnological variability and pelagic fish abundance (Stolothrissa tanganicae and Lates stappersii) in Lake Tanganyika
Plisnier, P. D.; Mgana, H.; Kimirei, I. et al

in Hydrobiologia (2009), 625(1), 117-134

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See detailAge and the time lag method
Delhez, Eric ULg; Deleersnijder, Eric

in Continental Shelf Research (2008), 28(8), 1057-1067

The time lag method is one of the most straightforward methods used to estimate transit times from experimental data and is therefore widely used. The transit time between two points is estimated from the ... [more ▼]

The time lag method is one of the most straightforward methods used to estimate transit times from experimental data and is therefore widely used. The transit time between two points is estimated from the analysis of time series taken at these two points that suggest the propagation of a signal from one point to the other. To account for the distortion of the signal during its propagation between the two points an optimum time lag can be estimated by the analysis of the cross-correlation of the two time series. This study clarifies the relation between the transit time estimated by the time lag method and the well-defined concept of the age of a water mass. It is shown, through simplified process models, that the time lag method systematically underestimates the true mean age. The error can be quantified by means of a dimensionless parameter which is the inverse of a Peclet number based on a characteristic length given by the ratio of the velocity of the flow to the frequency of the signal. (c) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThe leaky funnel model, a metaphor of the ventilation of the World Ocean as simulated in an OGCM
Mouchet, Anne ULg; Deleersnijder, Eric

in Tellus : Series A (2008), 60(4), 761-774

It is seen that an idealized model may suggest an appropriate scaling of the water age in the World Ocean, which is a measure of the ventilation rate. We use a 1-D advection-diffusion model in which the ... [more ▼]

It is seen that an idealized model may suggest an appropriate scaling of the water age in the World Ocean, which is a measure of the ventilation rate. We use a 1-D advection-diffusion model in which the deep ocean is represented as a leaky funnel, allowing recirculation towards the surface. The analytical solutions to the steady-state problem are readily obtained. The three parameters of the leaky funnel model are estimated in such a way that the behaviour of the domain-averaged water age be as similar as possible to that derived from a 3-D model in a series of sensitivity runs. The agreement between both sets of mean ages is excellent, with a linear correlation coefficient very close to unity. A good agreement is also found for the age of radioactive tracers and the associated radioages. The parameters of the leaky funnel model have a clear physical meaning, that is, the order of magnitude of the horizontal velocity, the mean length of water parcel trajectories in the deep ocean, and a horizontal diffusivity scale. The values of all of them turn out to be consistent with our current knowledge of the World Ocean circulation. [less ▲]

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See detailTimescale- and Tracer-Based Methods for Understanding the Results of Complex Marine Models
Deleersnijder, Eric; Delhez, Eric ULg

in Estuarine Coastal & Shelf Science (2007), 74

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See detailTimescale- and tracer-based methods for understanding the results of complex marine models
Deleersnijder, Eric; Delhez, Eric ULg

in Estuarine Coastal & Shelf Science (2007), 74(4), -

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See detailOvershootings and spurious oscillations caused by biharmonic mixing
Delhez, Eric ULg; Deleersnijder, Eric

in Ocean Modelling (2007), 17(3), 183-198

Biharmonic mixing is often used in large scale numerical models of the ocean because of its scale selectivity; it effectively damps small scale noise and leaves the large scale dynamics nearly unaffected ... [more ▼]

Biharmonic mixing is often used in large scale numerical models of the ocean because of its scale selectivity; it effectively damps small scale noise and leaves the large scale dynamics nearly unaffected. The biharmonic operator lacks however positiveness and monotonicity and can therefore produce unphysical results exhibiting spurious overshootings and oscillations. This problematic behaviour cannot be avoided by the addition of an ordinary Laplacian diffusion term. It appears in both continuous and discrete approaches/solutions in both unbounded and bounded domains. The overshootings and oscillations are induced by the strong damping of the smaller scale modes and are therefore comparable to the Gibbs' phenomenon. With appropriate boundary conditions, the variance of the field decreases monotonically and the oscillations are expected to remain small. The lack of positiveness is however a severe drawback for (dynamic) tracer studies. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailUnstructured, anisotropic mesh generation for the Northwestern European continental shelf, the continental slope and the neighbouring ocean
Legrand, Sebastien; Deleersnijder, Eric; Delhez, Eric ULg et al

in Continental Shelf Research (2007), 27(9), 1344-1356

A new mesh refinement strategy for generating high quality unstructured meshes of the Northwestern European continental shelf, the continental slope and the neighbouring ocean is presented. Our objective ... [more ▼]

A new mesh refinement strategy for generating high quality unstructured meshes of the Northwestern European continental shelf, the continental slope and the neighbouring ocean is presented. Our objective is to demonstrate the ability of anisotropic unstructured meshes to adequately address the challenge of simulating the hydrodynamics occurring in these three regions within a unique mesh. The refinement criteria blend several hydrodynamic considerations as the tidal wave propagation on the continental shelf and the hydrostatic consistency condition in steep areas. Several meshes illustrate both the validity and the efficiency of the refinement strategy. The selection of the refinement parameters is discussed. Finally, an attempt is made to take into account tidal ellipses, providing another cause for anisotropy in the mesh. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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