References of "Nihoul, Jacques"
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See detailA simple two species ecological model exhibiting chaotic behaviour
Beckers, Jean-Marie ULg; Nihoul, Jacques ULg

in Mathematical & Computer Modelling (1995), 21(6), 3-11

The classical prey-predator model of Lotka-Volterra is revisited. Instead of constant growth rates, a modulated growth rate for the prey is used. It is shown that in this very simple case, the resulting ... [more ▼]

The classical prey-predator model of Lotka-Volterra is revisited. Instead of constant growth rates, a modulated growth rate for the prey is used. It is shown that in this very simple case, the resulting system's evolution may become nonlinearly resonant. This shows that complex behaviour is not necessarily related to complex systems. [less ▲]

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See detailThe hydrodynamics of the Western Mediterranean Sea
Euromodel group; Nihoul, Jacques ULg; Beckers, Jean-Marie ULg et al

Report (1995)

Euromodel is devoted to process studies in relation to the description, understanding and simulation of the seasonal and mesoscale variability of the general circulation of the Western Mediterranean. Deep ... [more ▼]

Euromodel is devoted to process studies in relation to the description, understanding and simulation of the seasonal and mesoscale variability of the general circulation of the Western Mediterranean. Deep water formation drives the large cyclonic gyre observed in the northern basin. Some seasonal and mesoscale characteristics of the Northern, Tyrrhenian and Western Corsican Currents are specifies. The flow throuch the strait of Gibraltar is not hydraulically controlled. Potential vorticity conservation and changes in the meridional pressure gradients explain the formation of the western Alboran Sea gyre. Cyclonic eddies at its periphery are observed and modelled. The Almeria-Oran jet-front system is described in terms of geostrophic adjustment of Modified Atlantic Water and Mediterranean Water. Algerian eddies are linked to baroclinic instability of the current. A cyclonic circulation around the continental slope in the whole western basin is observed at depth. Upper ocean mesoscale variability is related to downward penetration of near-inertial motions as observed near the Catalan front. In the Balearic Sea, spatial and temporal variability of two shelf / slope fronts influences the large scale dynamics. The MAST 1 phase of Euromodel, initiales a numerical simulation of the Western Mediterranean : the sole forcing by the density gradients throuh the straites of Gibraltar and Sicily quaalitatively reproduces the basin scale cycloni surface and intermediate flows and the coastal currents. [less ▲]

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See detailInvestigation of the Western Mediterranean's hydrodynamics with the GHER three-dimensional primitive equation model
Beckers, Jean-Marie ULg; Brasseur, P.; Djenidi, Salim ULg et al

in Coastal and Estuarine Studies (1994), 46

A three-dimensional, non-linear, primitive equation model with turbulent closure developed at the GeoHydrodynamics and Environment Research Laboratory (GHER), University of Liège, is designed to define ... [more ▼]

A three-dimensional, non-linear, primitive equation model with turbulent closure developed at the GeoHydrodynamics and Environment Research Laboratory (GHER), University of Liège, is designed to define marine weather-like processes ranging from mesoscale tides and storm surges, to synoptic frontal and eddy structures, to macroscale slowly-varying currents characteristic of the so-called “general circulation”. The model is applied here to the study of the hydrodynamics of the western Mediterranean as both a metagnostic (i.e. system-oriented) model and a diagnostic (i.e. process-oriented) model with both models allowed to run simultaneously and interactively. Critical processes such as deep water formation and the instabilities of the Algerian Current, are studied to provide a basic understanding of the physics needed to adequately parameterize sub-grid scale processes in the basin wide metagnostic model. This general circulation model provides boundary conditions for the finer grid diagnostic studies as well as the general overview of the basin's hydrodynamics. Further improvement is achieved by concurrent use of a variational inverse model to provide initial data fields and boundary conditions for the direct model. In turn, the metagnostic model provides hydrodynamic constraints which are imposed to the variational principle to ensure an interpolation/extrapolation of data compatible with the system's hydrodynamics. Results viz (i) a diagnostic study of the Algerian Current, (ii) a metagnostic study of the seasonal variability of the western Mediterranean Sea, are presented and compared with observations and with results of simpler (quasi-geostrophic, reduced gravity, etc.) models. Possible improved hydrodynamic forecasts of seasonal and interannual variability with the 3D primitive equation model is discussed with particular attention to the forecast's sensitivity to initial and boundary conditions. [less ▲]

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See detailResults of metagnostic (system-oriented) and diagnostic (process-oriented) models
Beckers, Jean-Marie ULg; Haus, J.; Nihoul, Jacques ULg et al

in Progress in Belgian Oceanographic Research (1993)

After a review of the Mediterranean system, and the justification of the scientific interest, we examine the type of model (scope, purview and resolution) used for the description and simulation of the ... [more ▼]

After a review of the Mediterranean system, and the justification of the scientific interest, we examine the type of model (scope, purview and resolution) used for the description and simulation of the Mediterranean circulation from a system-oriented view and a process-oriented view. These two aspects of mathematical simulations are then illustrated by two examples: a) The simulation of the month to month variability of the general circulation in the Western Mediterranean Sea shows the main physical features, but the choice of initial conditions is crucial for a realistic simulation, and an inverse model is proven to be absolutely necessary for a valuable prognostic model. b) Secondly, a high resolution simulation of the Algerian Current instability is performed. It is well known that the Atlantic water flows along the Algerian coast as a light water intrusion. This current is unstable, and mesoscale activities generate cyclones and anticyclones, but only the latter grow enough to get separated from the mean flow. Numerical simulations, in an idealized case, and reality show strong instabilities that are analyzed by energy budgets. It is suggested that the instabilities are primarily baroclinic, which is consistent with initial vertical movements at the front. [less ▲]

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See detailModelling the Coastal Ocean’s Complex Ecohydrodynamics. A case study; the Northern Bering Sea
Nihoul, Jacques ULg; Adam, Paul; Djenidi, Salim ULg et al

in Progress in Belgian Oceanographic Research (1993)

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See detailSub-mesoscale Air-sea Interactions
Nihoul, Jacques ULg; Djenidi, Salim ULg

in Journal of Marine Systems (1993), 4(2-3),

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See detailThree-dimensional General Circulation Model of the Northern Bering Sea’s Summer Ecohydrodynamics
Nihoul, Jacques ULg; Adam, Paul; Brasseur, Pierre et al

in Continental Shelf Research (1993), 13(5-6), 509-542

The main features of the northern Bering Sea's summer ecohydrodynamics are investigated with the help of two three-dimensional—direct and inverse—models developed at theGeoHydrodynamics ... [more ▼]

The main features of the northern Bering Sea's summer ecohydrodynamics are investigated with the help of two three-dimensional—direct and inverse—models developed at theGeoHydrodynamics andEnvironmentResearch Laboratory of the University of Liège (GHER). Each model consists of two interacting sectorial submodels for (i) the general circulation hydrodynamics and synoptic structures, and (ii) the associated plankton ecosystem dynamics. The direct model is used to simulate, from an initial state compatible with historical, climatological and all available data pertinent to the summer season, a typical overview of the northern Bering Sea's ecohydrodynamics during the summer. The inverse model is applied in a two-fold perspective: (i) the reconstruction of typical summer distributions of temperature and salinity by using more than 1500 CTD profiles measured during the months of July, August and September, in the course of the ISHTAR program; (ii) considering the observations from specific ISHTAR surveys as quasi-synoptic, the reconstruction of individual data fields in order to provide additional information to assess the variability of the system. The model's predictions indicate that the summer dynamics are dominated by a few cogent semi-permanent and reproducible mechanisms which govern the main water mass transports, the upwellings, the fronts and the subsequent seasonal patterns of primary and secondary productions. The general circulation fields calculated by the direct model are considered as a standard of reference to give a coherent interpretation of—local and often instantaneous—observations, process studies and related results, in the context of the natural variability of the system. The simulated flow pattern has been validated, using the set of current measurements provided by 1985 and 1986 ISHTAR moorings. The contribution of the Anadyr Stream to the northward transport is reproduced qualitatively and quantitatively. The vertical motions—undetectable from direct experiments—are computed by the model, and represent one of the most efficient constraints on the ecohydrodynamics. For instance, the strong upwelling located along the Siberian coast—the existence of which was only presumed until recently—is now correctly estimated in position and intensity. The exceptionally high concentrations of nutrients found in the upwelled water turn this hydrodynamic structure into a catalyst element for the development of biological species in the region. The pattern of primary production shows two successive maxima: the first appears as a direct consequence of the frontal conditions associated with the Anadyr Stream, whereas the second develops further north, in the Chukchi Sea. The results display a fairly good agreement with the classical descriptions induced from observations, and suggest that the advection-growth coupling is the main physical conditioning factor for biological processes. [less ▲]

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See detailSub-mesoscale Air-sea Interactions
Nihoul, Jacques ULg; Djenidi, Salim ULg

in Journal of Marine Systems (1993), 4(2-3),

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See detailRegional modelling of the biogeochemical cycles in the Western Mediterranean (EROS 2000)
Djenidi, Salim ULg; Martin, J. M.; Beckers, Jean-Marie ULg et al

in Barthel, K. G.; Bohle-Carbonell, C.; Weydert, M. (Eds.) Marine Sciences and technologies (1993)

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See detailCoastal Ocean Modelling
Nihoul, Jacques ULg; Djenidi, Salim ULg

in Bordomer 92 (1992)

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See detailIce Covered Seas and Ice Edges: Physical, Chemical and Biological Processes and Interactions
Nihoul, Jacques ULg; Djenidi, Salim ULg

Book published by Elsevier Science (1992)

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See detailModelling the interaction of the deep ocean and the shelf and coastal seas
Nihoul, Jacques ULg; Djenidi, Salim ULg

in Journal of Marine Systems (1992), 3(4-5), 307-308

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See detailModel of the algerian currents instability
Beckers, Jean-Marie ULg; Nihoul, Jacques ULg

in Journal of Marine Systems (1992), 3(4-5), 441-451

A preliminary ''small-perturbation'' analytical study of a non-dissipative idealized model of the Algerian Current is made, with the aim of identifying major characteristic scales and investigating the ... [more ▼]

A preliminary ''small-perturbation'' analytical study of a non-dissipative idealized model of the Algerian Current is made, with the aim of identifying major characteristic scales and investigating the reality of possible classical instability mechanisms. The simple configuration is shown to be stable, from a linear perturbation point of view. The GHER 3D Primitive Equation Model is then applied to a more realistic investigation of the Algerian Current. The GHER model is non-linear, three-dimensional, with turbulent closure, mode splitting and a sigma-Coordinate formulation. The numerical simulation shows the development and mature pattern of the instability in excellent agreement with the observations. The relative importance of the existence of a coastal boundary layer, the nature of the initial perturbation, baroclinic and non-linear effects on the instability mechanism is discussed. [less ▲]

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See detailModelling the Western Mediterranean : from hydrology to hydrodynamics
Beckers, Jean-Marie ULg; Djenidi, Salim ULg; Nihoul, Jacques ULg

in Water Pollution Research (1991), 28

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See detailProgramme on Coastal Ocean Advanced Science and Technology Study (COASTS)
IOC Expert Group; Djenidi, Salim ULg; Nihoul, Jacques ULg

Report (1991)

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See detailMarine hydrodynamical and biogeochemical model: general 3D circulation model of the Western Mediterranean Sea
Nihoul, Jacques ULg; Beckers, Jean-Marie ULg; Brasseur, P. et al

in Martin, Jean-Marie; Barth, Hartmut (Eds.) EROS 2000 (European River Ocean System) (1991)

The GHER 3D OGCM has been applied to the study of the general circulation of the Western Mediterranean. Taking into account inflows and outflows through the Straits and the atmospheric forcings, the model ... [more ▼]

The GHER 3D OGCM has been applied to the study of the general circulation of the Western Mediterranean. Taking into account inflows and outflows through the Straits and the atmospheric forcings, the model visualizes the horizontal and vertical motions of water masses and their month to month variability. The results of the basin scale provides boundary conditions for a finer grid nested model of the Gulf of Lion and of the Rhone rivers's plume. [less ▲]

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