• Evaluation of Mineral Dust Sources in North Africa using Model Simulated and Satellite Retrieved TOMS Absorbing Aerosol Indices
  Masaru Yoshioka, Jean-Louis Dufresne, Natalie Mahowald, Chao Luo
  2nd Workshop on Mineral Dust, Paris, 10-12 Septembre 2003

• Future changes in global and regional climate,
  I.I. Mokhov, J.-L. Dufresne, V.Ch. Khon, H. Le Treut, V.A. Tikhonov,
  IUGG-2003 , Sapporo
• Longwave radiative exchange analysis of cloudy atmospheres with a net exchange formulation
  V. Eymet, S. Blanco, J-L. Dufresne, R. Fournier
  EGS-AGU-EUG Joint Assembly, Nice, France, 06 - 11 April 2003
  Abstract. The Next Exchange Formulation (NEF) is an alternative to the usual radiative transfer equation. It was proposed in 1967 by Green for atmospheric sciences and by Hottel for engineering sciences. Until now, the NEF has been used only in a very few cases for atmospheric studies. Recently we have developed a longwave radiative code based on this formulation for a GCM of the Mars planet. Here, we will present results for the Earth atmosphere, obtained with a Monte Carlo Method based on the NEF. In this method, the fluxes are no more considered. The basic variables are the net exchange rates (NER) between each pair of atmospheric layer {i,j}, i.e. the radiative power emitted by i and absorbed by j minus the radiative power emitted by j and absorbed by i. The graphical representation of the NER matrix highlight the radiative exchanges which dominate the radiative budget of the atmosphere and allows one to have a very good insight of the radiative exchanges. Results will be shown for clear sky atmosphere, cloudy atmosphere and atmosphere with dust aerosols. The role of scattering in the longwave radiative exchanges will also be analyzed. The calculation of sensitivity parameter being automatically implemented in the Monte Carlo Method, a complementary sensitivity analysis will be presented that examines how radiative exchanges depend on concentrations profiles of main absorbing and scattering species.

• Evaluation of Disturbed Soils in North Africa as Source of Mineral Dust Aerosols using Model Simulated and Satellite Observed TOMS AI
  M. Yoshioka, J-L. Dufresne, N. Mahowald, C. Luo
  EGS-AGU-EUG Joint Assembly, Nice, France, 06 - 11 April 2003

• Improvements of the atmospheric general circulation model LMDZ in the perspective of the development of the new IPSL coupled model.
  F. Hourdin, P. Braconnot, Sandrine Bony, Ionela Musat, Laurent Fairhead, Jean-Louis Dufresne, Jean-Yves Grandpeix
  EGS-AGU-EUG Joint Assembly, Nice, France, 06 - 11 April 2003
  Abstract. In the course of the development of the IPSL coupled model, a significant work has been devoted during the last three years to the improvement of the atmospheric physics.
  Switching from Tiedtke (Mon. Wea. Rev., 117:1179-1800, 1989) to Emanuel (J. of Atmopsh. Sci., 48:2313-2335, 1991) convection scheme resulted in a better distribution of convective precipitations in the tropics, with a significant enhancement on Amazonia and Africa during the rain season. However, when using the original cloud scheme of LMD (Le Treut and Li, Clim. Dyn., 5:175-187, 1991), the model was strongly underestimating short wave radiative forcing of convective clouds, even in those regions were the precipitation itself was greatly improved. This problem was solved by introducing a more sophisticated parameterization (Bony and Emanuel, J. Atm. Sci., 58:3158-3183, 2001) based on a generalized log normal PDF of the subgrid scale distribution of total water (in place of the old top-hat distribution). More importantly, in this new parameterization, the width of the distribution is not imposed but computed interactively with the convection scheme so as to simulate the proper incloud water content.
  Finally, a particular care was given to a rewritting of an interface between a four-column boundary layer scheme and four sub-surfaces (ocean, continents, sea-ice and glaciers) for each GCM mesch, insuring a numerical conservation of energy and water. This interface is used for coupling with both oceans (ORCA) and continental surfaces (ORCHIDEE).
  We present the impact of these recent updates focussing on those aspects which were crucial for the improvement of the climatology of the coupled model (joint poster) such as energy balance at the top of the atmosphere and simulation of surface fluxes, in particular as influenced by convection and clouds.

• Towards an Earth System Model : Key Results of the new IPSL Coupled Model
  P. Braconnot for The IPSL group on coupled modelling
  EGS-AGU-EUG Joint Assembly, Nice, France, 06 - 11 April 2003
  Abstract. The estimate of future climate change and its impact on the environment needs an understanding on the underlying complex interactions between the atmosphere, the ocean, and the land surface. Furthermore, these components are coupled through the cycles of energy, water, but also biogeochemical cycles such as carbon, nitrogen, ozone, ÇE One of the goal of the IPSL global modelling community is to study how these different coupling can modulate the climate change signal and what are the feedbacks in the Earth system that control its response to a perturbation such as the anthropogenic emissions of greenhouse gases. To achieve these goals, we recently developed a new version of the IPSL coupled model. The dynamical and physical part of the model includes the LMDZ atmospheric model, the ORCA ocean model, the ORCHIDEE surface schema and the Louvain la neuve sea-ice model. Surface fluxes and variables needed to couple the oceanic and atmospheric models are exchanged through the oasis coupler. The model benefits from - a new modelling environment (modipsl, ioipsl), - a rewriting of the atmospheric boundary layer which allows for a convenient coupling between the surface model and the atmosphere, - new developments in the interpolation scheme designed to conserve fluxes at the ocean interface in a global, but also local way, - a new river routine scheme, - a new convection scheme and several atmospheric adjustments - potential coupling with the carbon cycle and the tropospheric chemistry

2002

• Importance and Parameterization of Longwave Radiative Scattering by Mineral Aerosols
  J.L. Dufresne, C. Gautier, P. Ricchiazzi;
  Twelfth ARM Science Team Meeting, St. Petersburg, Florida, 8-12 April 2002

2001

• Importance and Parameterization of Longwave Radiative Scattering by Mineral Aerosols
  J.L. Dufresne, C. Gautier, P. Ricchiazzi;
  Fall Meeting of AGU, San Francisco, 10-14 December, 2001
  Eos Trans. AGU, 82(47), Fall Meet. Suppl., Abstract A22A-0105, 2001
  Abstract. The effect of scattering is not always included in longwave models of radiative forcing due to mineral aerosols. In this presentation, we quantify and highlight the importance of scattering in the longwave domain for a wide range of conditions commonly encountered during dust events. We show that the neglect of scattering may lead to an underestimate of longwave aerosol forcing. This underestimate may reach 50\% of the forcing at the top of atmosphere and 15\% at the surface for aerosol effective radius greater than a few tenths of a micron. In contrast, the heating rate inside the atmosphere is only slightly affected by aerosol scattering: neglecting it leads to an underestimate by no more than 10\% of the extra cooling caused by aerosols. The radiative codes based on k-distribution or exponential sum fit methods may consider scattering in the longwave if appropriate algorithms are implemented. But the so called ``absorptivity/emissivity formulation'' is also used in many GCM longwave radiative codes and is unable to deal with multiple scattering effects. For these radiative codes, we present a parameterization to approximate the longwave radiative scattering by mineral aerosols.

• How positive is the feedback between climate change and the carbon cycle?
  Friedlingstein, P., Dufresne, J., Cox, P., and Rayner, P. J.
  4th International Scientific Conference on the GEWEX, Paris, France, 10-14 september , 2001.
  Abstract. Future climate change induced by atmospheric emissions of greenhouse gases is believed to have a negative impact on the global carbon cycle. Several offline studies focusing either on the marine or on the terrestrial carbon cycle highlighted such potential adverse effects. Two recent online studies, using ocean-atmosphere general circulation models coupled to land and ocean carbon cycle models, investigated in a consistent way, the feedback between the climate change and the carbon cycle. These two studies used observed anthropogenic CO2 emissions for the 1860-1995 period and IPCC scenarios for the 1995-2100 period to force the climate-carbon cycle models. The study from the Hadley Centre group, showed a very large positive feedback, atmospheric CO2 reaching 950 ppmv by 2100 if future climate impacts on the carbon cycle, but only about 700 ppmv if the carbon cycle is assumed to be insensitive to the climate change. With the IPSL coupled climate-carbon cycle model, we simulated a much smaller positive feedback: climate impact on carbon cycle leads by 2100 to an addition of less than 100 ppmv in the atmosphere. Here we summarize these two studies, highlighting on the main mechanisms responsible for the differences between the Hadley Centre and the IPSL results. Respective sensitivities of the terrestrial carbon cycle (vegetation and soil) to the climate change and to increased CO2 are key controllers on the magnitude of the positive feedback between climate change and the global carbon cycle. This work is preliminary to C4MIP, a new IGBP/GAIM initiative, which aims to compare and evaluate climate-carbon cycle models.

• How positive is the feedback between climate change and the carbon cycle?
  Friedlingstein, P., Dufresne, J., Cox, P., and Rayner, P. J. ;
  Sixth International Carbon Dioxide Conference Program, Sendai, Japan, October 1-5, 2001

• Interactions Between Future Climate Change and Carbon Cycle in the Land Biota.
  M. Berthelot, P. Friedlingstein, P. Ciais, P. Monfray, J.L. Dufresne, H. Le Treut and L. Fairhead;
  Sixth International Carbon Dioxide Conference Program, Sendai, Japan, October 1-5, 2001

• Scattering effect of Mineral Aerosols.
  Dufresne J-L, Gautier C, Ricchiazzi P.;
  ARM Science Team Meeting, Atlanta, 19-23 march 2001

2000

• Parameterization of the Radiative Effects of Mineral Aerosols.
  Dufresne J-L, Gautier C, Ricchiazzi P.;
  AGU fall meeting, San Francisco, december 2000
  Abstract. Observations and models have demonstrated the importance of the radiative forcing by mineral aerosol on the Earth's energy budget. However, relatively little is known about how these aerosols affect atmospheric circulation through modification of the local heating rate. To investigate this issue, we are developing a parameterization of the radiative effects of mineral aerosols that covers the observed range of North African dust plumes. Our goal is to develop a parameterization that faithfully characterizes radiative properties of these aerosols, but is still practical for use in GCM's. The parameterization is based on narrow band calculations using a moderate resolution radiative transfer code. Scattering effects are included in both short and longwave spectral regions. This study will address the following issues: - Effect of scattering on long wave radiation. Determination of conditions for which simple non-scattering radiation models are appropriate. - Impact of vertical structure, particularly as it pertains to longwave flux divergence. Observed vertical aerosol profiles will be used. - Evolution of radiative properties as a function of time and distance from the initial wind entrainment. Here, we will focus on how heating rate changes with physical properties of aerosols (refractive index, diameter, composition...).

• Climate and carbon cycle changes under IPCC scenarios of future anthropogenic emissions.
  Friedlingstein P , Dufresne J-L, Berthelot M, Bopp L, Ciais P, Fairhead L, Letreut H, Monfray P;
  AGU fall meeting, San Francisco, december 2000
  Abstract. Increased atmospheric CO2 due to anthropogenic emissions is very likely to affect the climate system. This latter is one of the main driver of the carbon cycle which will therefore respond to that perturbation. Here using an atmosphere-ocean general circulation model coupled to a land and ocean carbon cycle models we simulate the evolution of climate and carbon for the historical period (1850-2000) and for the 21st century. Our model reproduces remarkably well the evolution of climate and carbon over the historical period. For the future we show that climate change will affect negatively carbon uptake, particularly on land. As a result, the atmospheric CO2 will be 20% higher at 2100 if the climate change is taken into account. However, this larger atmospheric CO2 enhances the geochemical exchange of CO2 with the land and ocean reservoirs. Altogether the land uptake is negatively affected by the climate change. For the ocean, the climate impact is conterbalanced by the additional CO2 mainly coming from the climate perturbation on the biosphere.

• Feedbacks between the carbon cycle and the climate change.
  P. Monfray, M. Berthelot, L. Bopp, P. Ciais, J.L. Dufresne, L. Fairhead, P. Friedlingstein, H. LeTreut;
  AGU spring meeting, Washington DC, May 30 - June 3, 2000
  Abstract. In simulations carried out to study anthropogenic climate change, the atmospheric CO2 increase used has always been prescribed by different scenarii, like, for example, those suggested by the IPCC. The rate of CO2 increase depends on the rate of anthropogenic emissions and on the uptake by the ocean and the continental biosphere. However, recent studies suggest that those CO2 uptakes may be reduced by the climate change thus introducing a positive feedback in the carbon-climate system. We will present here two estimates of this positive carbon-climate feedback. Our first estimation uses the results of a classical climate simulation carried out with the IPSL AOGCM where the CO2 increase is fixed at 1\%/year (CMIP). These results are used to carry out two simulations of the carbon cycle: in the first, the carbon cycle models do not respond to climate change whereas in the second, they do. We can thus estimate the feedback between the carbon cycle and climate. A second estimate of this feedback uses results from a fully coupled carbon-climate simulation where anthropogenic CO2 emissions are prescribed from 1850 up to 2050 using IPCC-TAR scenario. Atmospheric CO2, climate change, and carbon cycle are computed in a consistent way with the IPSL climate-carbon model. Potential climate impacts on marine and continental biomass

• Coupled Carbon-Climate Simulations using the IPSL Coupled Model
  J-L.Dufresne, L.Bopp, P. Ciais, L. Fairhead, P. Friedlingstein, H.Le Treut, P.Monfray,
  EGS XXV General Assembly, Nice, France, 25-29 April 2000
  Abstract. In simulations carried out to estimate anthropogenic climate change, the atmospheric CO2 increase is commonly prescribed using different emission scenarii, like, for example, those assembled by the IPCC. The rate of atmospheric CO2 increase depends on the rate of these prescribed antropogenic emissions (changes in land use and fossil CO2 emissions) and on the uptake by the ocean and the biosphere. Carbon uptake by oceans and continents is not independent of climate change. Recent studies have suggested that over the next decades, the CO2 uptakes may be reduced by climate change thus introducing a positive feedback in the carbon-climate system. In order to study this feedback within the fully coupled carbon-climate system, we have recently added comprehensive, spatially resolved, oceanic and biospheric carbon models to the IPSL coupled AOGCM. The model configuration will be described and results from two 240 year long simulations carried out with it will be presented. The first simulation is a control simulation with no anthropogenic CO2 emissions. The second simulation is a scenario simulation using historical anthropogenic emissions from 1860 to 1990 and, from 1990 to 2100, emissions following the SRES98-A2 IPCC scenario. At the time of abstract submission the pertirbed experiment has reached year 1985, and the simulated CO2 content is realistic.

• Feedback estimate between the carbon cycle and the climate system.
  P. Friedlingstein, L.Bopp, P. Ciais, J-L.Dufresne, L. Fairhead, H.Le Treut, P.Monfray;
  EGS XXV General Assembly, Nice, France, 25-29 April 2000
  Abstract. In simulations carried out to study anthropogenic climate change, the atmospheric CO2 increase used has always been prescribed by different scenarii, like, for example, those suggested by the IPCC. The rate of CO2 increase depends on the rate of anthropogenic emissions and on the uptake by the ocean and the biosphere. However, recent studies suggest that those CO2 uptakes may be reduced by the climate change thus introducing a positive feedback in the carbon-climate system.
  We will present here two estimates of this positive carbon-climate feedback. Our first estimation uses the results of a classical climate simulation carried out with the IPSL AOGCM where the CO2 increase is fixed at 1%/year (CMIP). These results are used to carry out two simulations of the carbon cycle: in the first, the carbon cycle models do not respond to climate change whereas in the second, they do. We can thus estimate the feedback between the carbon cycle and climate.
  A second estimate of this feedback uses results from a fully coupled carbon-climate simulation now in progress.

• Potential impact of climate change on marine production and CO2 uptake by the ocean.
  L.Bopp, P.Monfray, O.Aumont, J-L.Dufresne, H.Le Treut, G.Madec, L.Terray, J. Orr;
  SOLAS Conference, Kiel, Germany , 20-24 Feb 2000
  Abstract. In this study, using two different ocean biogeochemical schemes and two different atmosphere-ocean coupled general circulation models, we investigate the effect of future climate change on marine biomass. Our prognostic models of ocean bio-geochemistry were imbedded in an oceanic general circulation model, coupled to two different atmospheric general circulation models. Those coupled models were used without flux corrections to simulate climate response to increase greenhouse gases (+ 1% CO2/yr for 80 years).
  At 2xCO2 in 2060, both reduced nutrient supply and increased light efficiency re-sulted from increased stratification in the upper ocean. Both effects lead to signi-ficant large-scale changes (from -15% in the tropics to +10% in the Southern Ocean for the zonal mean) and moderate global decrease (about -5%) of marine export production. This conclusion is valid for both biogeochemical schemes and both coupled models. Furthermore, we infer from our simulations the time and location of a possible detection of human impact on marine biogeochemistry. Ye-ar of detection is deduced from a comparison between simulated natural variabi-lity and simulated anthropogenic trend of surface chlorophyll.

• Radiative transfer modeling for radiation-chemistry coupling analysis

  de-Guilhem-de-Lataillade-A; El-Hafi-M; Fournier-R; Dufresne-J-L;
  Rayonnement et milieux semi-transparents : Chatenay Malabry, France, 2 fevrier 2000
  Abstract. This study is devoted to the prediction of pollutant formation inside combustion chambers. In order to control minor species emissions, considering the high sensitivity of kinetic chemistry to temperature, it is required that physical analysis include detailed description of all heat transfer processes. As far as radiation is concerned, one may state that no numerical model is available at date that meets the requirements in terms of geometrical description and accuracy. The present work discusses an alternative approach that combines an accurate Monte Carlo algorithm with a simple Taylor expansion of radiative exchanges as function of temperatures and concentrations. Accurate models can be designed on this basis that can be easily coupled to detailed kinetics models.

1999

• Impact du changement du climat sur la productivité marine et l'absorption de CO2 anthropique.
  L.Bopp, P.Monfray, O. Aumont,J.C.Orr, J-L.Dufresne, H.LeTreut, L.Terray, S.Valcke, G.Madec;
  JGOFS-France. Journées "Synthèse & Modélisation", Toulouse, 23-24 Septembre 99

• Biospheric carbon cycle response to global warming.
  Pierre Friedlingstein, Patrick Monfray And Philippe Ciais, Herve Letreut, Jean-Louis Dufresne;
  The 22nd General Assembly of the IUGG , The University of Birmingham, UK, 18-30 July 1999.

• Impact of climate change on marine biomass and air-sea $CO_2$ fluxes.
  L.Bopp, P.Monfray, O.Aumont, J.C.Orr, G.Madec, L.Terray, J-L.Dufresne, H.Le Treut;
  EGS XXIV General Assembly, The Hague, The Netherlands, 19-23 April 1999
  Abstract. To investigate the effect of future climate change on marine biology and the ocean carbon cycle, we imbedded a prognostic model of ocean biogeochemistry in an oceanic general circulation model (OGCM). The same OGCM coupled to an atmospheric general circulation model, was used without flux correction to simulate climate response to increased greenhouse gases (+1% CO2/yr for 80 years). At 2xCO2 in 2060, both reduced nutrient supply and increased light efficiency resulted from increased stratification in the upper ocean. Both effects lead to significant large-scale changes in marine primary production (from -20% in the tropics to +5% in the Southern Ocean for the zonal mean). In regards to the increasing air-sea CO2 flux, we will differentiate increases due to rising atmospheric CO2 from reductions by climate change. Furthermore we will describe sensitivity studies made with two different prognostic biogeochemical schemes, and climate change forcing from two different coupled models.

• The influence of horizontal resolution in simulating low-frequency variability in a coupled ocean-atmosphere GCM.
  Laurent C., Le Treut H., Li Z.X., Fairhead L., Dufresne J.L.;
  EGS XXIV General Assembly, The Hague, The Netherlands, 19-23 April 1999

1998

• Marine biogeochemical response to climate change: Preliminary results with the IPSL-Paris coupled model.
  Bopp L., Monfray P., Aumont O., Dufresne J.L., Le Treut H., Madec G. And Orr J.;
  Third US-JGOFS SMP meeting, Durham, NH, Jul 1998.

• Principaux phénomènes régissant l'extension de la glace de mer
  Filiberti M.A., Dufresne J.L., Madec G.;
  Atelier de Modélisation de l'Atmosphère, Toulouse, France, 8-9 décembre 1998

• An analysis of tropical cloud radiative feedbacks in a coupled ocean-atmosphere model.
  S. Bony, J.-L. Dufresne, L. Fairhead;
  EGS XXIII General Assembly, Nice, France, 20-24 April 1998
  Abstract. Interactions between sea surface temperature, clouds and radiation play a fundamental role in the natural climate variability and in the climate sensitivity to radiative perturbations. We will present an analysis of these interactions in the IPSL global ocean-atmosphere coupled model. First, this analysis will be based on seasonal and interannual variations, and a comparison will be done with satellite observations. Then, we will consider a transient CO2 experiment of 80 years. A comparison of the tropical clouds feedbacks involved in the CO2 experiment and in the seasonal or interannual variations will be presented.

• Climate change due to a $CO_2$ increase as simulated by the IPSL coupled model.
  L. Fairhead, J.-L. Dufresne, H. Le Treut, L. Li;
  EGS XXIII General Assembly, Nice, France, 20-24 April 1998
  Abstract. The IPSL coupled model has been used for two eighty-year simulations: a control simulation with constant CO2 concentration and a scenario simulation with a 1% yearly increase in CO2 concentration. The absence of any flux corrections implies that an initial drift, which stays reasonable, is present in the two simulations. The general characteristics of the control simulation will be presented as well as the perturbations on the atmospheric and oceanic circulations due to the CO2 increase and particularly the SST perturbation which is peculiarly strong along the equator in the Pacific. Comparisons with similar experiments using a simple oceanic mixed layer as the oceanic component of the coupled model will be made to illustrate the part of oceanic circulation in the perturbed simulations.

• An assessment of the role of the atmosphere in antarctic sea-ice extension in global coupled models.
  M.-A. Filiberti and J.-L. Dufresne;
  EGS XXIII General Assembly, Nice, France, 20-24 April 1998

• Tropical Pacific variability simulated in a one hundred year run of a coupled general circulation model.
  Vintzileos A., Dufresne J.L., Le Treut H., Fairhead L.;
  EGS XXIII General Assembly, Nice, France, 20-24 April 1998

1997

• Some aspects of the thermodynamic ice-ocean interaction in a global OGCM.
  M.A. Filiberti, J.L.Dufresne, M.N. Houssais, M.Imbard, G. Madec;
  EGS XXII General Assembly, Viena, Austria, 21-25 April 1997

• Impact of sea ice / atmosphere interface modeling on the sea ice distribution in GCMs.
  J.L.Dufresne, L. Fairhead,M.A. Filiberti, M.N. Houssais;
  EGS XXII General Assembly, Viena, Austria, 21-25 April 1997
  Abstract. In sea ice covered regions, the ocean surface is highly heterogeneous (open water, new ice, thick pack ice...). The sea ice GCM we developed takes this heterogeneity into account by allowing various sea ice classes, whereas atmospheric models used in coupled GCMs usually allow only homogeneus surfaces. We analyse how the sea ice distribution is modified by the following different sea ice / atmosphere interface models :
  - the atmospheric model only considers one type of surface and fluxes over open water and over ice are similar
  - the atmospheric model only considers one type of surface but the atmospheric heat flux is redistributed through an interface that approximates the spatial heterogeneity of the underlying surface
  - the atmospheric model computes a separate flux over each of this type of surface
  These results were obtained with the LODYC ocean/sea ice GCM coupled to a simple bulk atmosphere and with the full coupled IPSL GCM.

• Raccordement Thermodynamiques Océan-Glace-Atmosphère
  . Dufresne J.L, Filiberti M.A., Grandpeix J.Y., Houssais M.N.;
  Atelier de Modélisation de l'Atmosphère, Toulouse, 2-3 décembre 1996
  Abstract. L'interface océan-glace de mer-atmosphère est extrêmement hétérogène. Le modèle de glace-océan du LODYC, utilisé par la communauté "GASTON", reproduit en partie cette hétérogénéité (mailles mixtes contenant de l'océan libre et différents types de glace) alors que les modèles d'atmosphère (Arpège, LMD 5) ne la reproduisent pas ou peu (mailles homogènes ou mailles mixtes océan libre - un seul type de glace). De plus, aux hautes latitudes, une maille atmosphérique recouvre un nombre élevé de mailles océaniques.
  Nous avons développé un modèle de raccordement qui répartit de façon différenciée les flux calculés par le modèle d'atmosphère sur les differents types de surface (oc\'ean libre ou vari\'et\'es de glace) en fonction de leur distribution statistique (fraction surfacique) et de leur caracteristiques individuelles (temp. de surface, albedo, etc...). Ce modèle de raccordement garantit la conservation des flux à l'interface.
  Nous présentons le modèle de raccordement et montrons la sensibilité de la fraction de glace à la méthode de répartition des flux. Nous abordons également le problème de la stabilité numérique du raccordement glace-atmosphère.

• Impacts du couplage des modè de glace de mer et d'Océan du LODYC.
  M.A. Filiberti, J.L. Dufresne, G. Madec, M.N. Houssais, M. Imbard;
  Atelier de Modélisation de l'Atmosphère, Toulouse, 2-3 décembre 1996, pp.63-68

• Essais sur le Merlin IV du Thermomêtre Anémomêtre Accoustique (T.A.A).
  D. Cruete, A. Marillier, J.L. Dufresne, J.Y. Grandpeix;
  Atelier Expérimentation et Instrumentation, Toulouse, 15-17 octobre 1996

• Modelling sea-ice/atmosphere thermodynamic coupling.
  Dufresne J.L, Grandpeix J.Y., Houssais M.N.;
  EGS XXI General Assembly, Den Hague, 6-10 May 1996
  Abstract. Two important issues of sea-ice model coupling with AGCM are considered.
  First the numerical oscillations induced by straight sea-ice/atmosphere coupling (in a fashion similar to the usual ocean/ atmosphere coupling) are investigated. A simple explanation is presented and exemplified : the oscillations are primarily due to the strong feedbacks between SST and surface flux beeing not properly taken into account.
  The second important issue is the quality of flux repartition between a homogeneous AGCM mesh and the amalgam of open water, thin ice, thick pack ice ... which make up a sea-ice model mesh.
  Practical solutions are given for both issues. A first implementation is tested in a thermodynamic sea-ice model coupled to a simple bulk formula atmosphere. The inclusion in the full coupled GCM of the IPSL is under way; first results are presented.