Global water and salt budget of the Aral Sea from 1960 to 1991.

Conference (2003, May)

Focusing on the global water and salt budget of the Aral sea from 1960 till 1991, a compilation of data available in the litterature is analysed with simple models and compared to the measured evolution ... [more ▼]

Focusing on the global water and salt budget of the Aral sea from 1960 till 1991, a compilation of data available in the litterature is analysed with simple models and compared to the measured evolution of the sea. [less ▲]

Influence of the Aral Sea negative water balance on its seasonal circulation and ventilation patterns : use of a 3D hydrodynamic model

in Geophysical Research Abstracts (2003, April), 5(09052), 2003509052

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic ... [more ▼]

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic model was adapted to address specifically the macroscale processes affecting the Aral Sea water circulation and ventilation. The particular goal of this research is to simulate the effect of lasting negative water balance on the 3D seasonal circulation, temperature, salinity and water-mixing fields of the Aral Sea. The original Aral Sea seasonal hydrodynamism is simulated with the average seasonal forcings corresponding to the period from 1956 to 1960. This first investigation concerns a period of relative stability of the water balance, before the beginning of the drying process. The consequences of the drying process on the hydrodynamic of the Sea will be studied by comparing this first results with the simulation representing the average situation for the years 1981 to 1985, a very low river flow period. For both simulation periods, the forcing considered are the seasonal fluctuations of wind fields, precipitation, evaporation, river discharge and salinity, cloud cover, air temperature and humidity. The meteorological forcings were adapted to the common optimum one-month temporal resolution of the available data sets. Monthly mean kinetic energy flux and surface tensions were calculated from daily ECMWF wind data. Monthly in situ precipitation, surface air temperature and humidity fields were interpolated from data obtained from the Russian Hydrological and Meteorological Institute. Monthly water discharge and average salinity of the river water were considered for both Amu Darya and Syr Darya river over each simulation periods. The water mass conservation routines allowed the simulation of a changing coastline by taking into account local drying and flooding events of particular grid points. Preliminary barotropic runs were realised (for the 1951-1960 situation, before drying up began) in order to get a first experience of the behaviour of the hydrodynamic model. These first runs provide results about the evolution of the following state variables: elevation of the sea surface, 3D fields of vertical and horizontal flows, 2D fields of average horizontal flows and finally the 3D fields of turbulent kinetic energy. The mean seasonal salinity and temperature fields (in-situ data gathered by the Russian Hydrological and Meteorological Institute) are available for the two simulated periods and will allow a first validation of the hydrodynamic model. Various satellites products were identified, collected and processed in the frame of this research project and will be used for the validation of the model outputs. Seasonal level changes measurements derived from water table change will serve for water balance validation and sea surface temperature for hydrodynamics validation. [less ▲]

Synthesis of water balance data and simulation of the shrinking process of the Aral Sea.

Conference (2001)

Dissection of the GHER turbulence closure scheme

in Journal of Marine Systems (1999), 21(1-4), 379-397

In this paper, the turbulence closure scheme implemented in the GHER hydrodynamic model is described in detail. Two case studies carried out in two contrasting conditions-one in the shallow, tide ... [more ▼]

In this paper, the turbulence closure scheme implemented in the GHER hydrodynamic model is described in detail. Two case studies carried out in two contrasting conditions-one in the shallow, tide dominated, north-western European continental shelf, and the other in the deep Mediterranean Sea-are used to identify the dominant terms of the equation for the turbulent kinetic energy, first theoretically, secondly from the results of the simulations. In both domains, the dominant terms are the local destruction and production terms, the vertical diffusion term and to a smaller degree, the time derivative. Advection and horizontal diffusion turn out to be negligible in most of the relevant cases for such large scale studies. This opens the way to simplifications and optimisations of the numerical models. (C) 1999 Elsevier Science B.V. All rights reserved. [less ▲]

Coupled 3D eddy-resolving general circulation model and ecosystem model applied to the Black sea.

in Ostrovskii, S.; Zatsepin, A. (Eds.) Oceanic Fronts and Related Phenomena (Konstantin Federov International Memorial Symposium) (1999)

Interdisciplinary approach and data assimilation in a Mediterranean ecosystem model

in EOS Transactions (1998), 79

Reconnaissance of the main Black Sea's ecohydrodynamics by means of a 3D interdisciplinary model

in Journal of Marine Systems (1998), 16(1-2), 85-105

A 3D interdisciplinary model has been used to test the sensitivity of the Black Sea’s ecosystem to physical processes. The hydrodynamical model of the general circulation has been built up, using the GHER ... [more ▼]

A 3D interdisciplinary model has been used to test the sensitivity of the Black Sea’s ecosystem to physical processes. The hydrodynamical model of the general circulation has been built up, using the GHER primitive equation model. A model with 15 km horizontal resolution and 25 vertical levels is used to compute the typical seasonal cycle. The model is forced by climatological monthly mean fields of temperature, salinity and wind stress at the air–sea interface; the river discharges of the Danube, Dnestr and Dnepr are taken into account. An ecosystem model at basin scale is then defined by a nitrogen cycle considering several phytoplankton and zooplankton sizes and including the microbial loop. The ecosystem model is embedded on-line into the 3D hydrodynamical model with a superimposed cycle for the light intensity. This model must be regarded rather as a first tool for testing the coupling of hydrodynamic and ecosystem submodels, while acquiring some preparatory assessment of the effect of physical processes on the ecodynamics. The results display a highly three-dimensional aspect with important horizontal and vertical variations, obviously imparted to the system by the physical processes horizontal and vertical advection, vertical mixing and diffusion, upwelling associated with light limitation at depth and sinking of dead organisms. In this paper, the results are described emphasizing the effects of the hydrodynamic constraints on the space–time distribution of the primary and secondary production. [less ▲]

Circulation of the western Mediterranean: From global to regional scales

in Deep-Sea Research Part II, Topical Studies in Oceanography (1997), 44(3-4), 531-549

A free-surface, three-dimensional, primitive equation model has been implemented with a horizontal resolution of 4.6 km to study the ocean circulation in the Gulf of Lions at time scales ranging from ... [more ▼]

A free-surface, three-dimensional, primitive equation model has been implemented with a horizontal resolution of 4.6 km to study the ocean circulation in the Gulf of Lions at time scales ranging from weeks to seasons. Numerical experiments have been conducted, in which the regional model is nested into a basin-scale model of the whole western Mediterranean. The global model is operated with a relatively coarse resolution (16 km) and provides boundary conditions at the open-sea boundaries of the regional domain. There is, however, no Feedback loop from the regional to the global model. The simulations are consistently driven with atmospheric fluxes computed from the output of the French PERIDOT meteorological forecasting system, between August 1988 and 1989. In addition to the initial conditions, in situ measurements of temperature and salinity are assimilated in the simulation of the general circulation, adopting a simple nudging technique to prevent an excessive drift of the model against climatology. The response of the regional model below and above the thermocline is discussed in the context of the prevailing meteorological situations. Some experiments give indications that a double-gyre system may develop from wind regimes that exhibit a cyclonic/anticyclonic wind stress curl. Advection-diffusion of passive tracers are also examined on the basis of the local hydrodynamic features, because this work has been conceived with the aim of determining the physical conditions in which ecological and biochemical processes develop at the interface between river mouths and the open ocean. (C) 1997 Elsevier Science Ltd. [less ▲]

Modelling the competition between two phytoplanktonic species

in Bulletin de la Société Royale des Sciences de Liège (1996), 65

Modelling the North Sea hydrodynamics in a management perspective

in Bulletin de la Société Royale des Sciences de Liège (1996), 65