Search

Your search keyword '"Hourdin, Christophe"' showing total 14 results
Start Over Author "Hourdin, Christophe"
14 results on '"Hourdin, Christophe"'

4. Net exchange reformulation of radiative transfer in the C[O.sub.2] 15-[micro]m band on Mars

Author

Dufresne, Jean-Louis, Fournier, Richard, Hourdin, Christophe, and Hourdin, Frederic

Subjects
Atmosphere -- Research, Mars (Planet) -- Discovery and exploration, Mars (Planet) -- Research, Earth -- Atmosphere, Earth -- Research, Earth sciences, Science and technology
Abstract

The net exchange formulation (NEF) is an alternative to the usual radiative transfer formulation. It was proposed by two authors in 1967, but until now, this formulation has been used only in a very few cases for atmospheric studies. The aim of this paper is to present the NEF and its main advantages and to illustrate them in the case of planet Mars. In the NEF, the radiative fluxes are no longer considered. The basic variables are the net exchange rates between each pair of atmospheric layers i, j. NEF offers a meaningful matrix representation of radiative exchanges, allows qualification of the dominant contributions to the local heating rates, and provides a general framework to develop approximations satisfying reciprocity of radiative transfer as well as the first and second principles of thermodynamics. This may be very useful to develop fast radiative codes for GCMs. A radiative code developed along those lines is presented for a GCM of Mars. It is shown that computing the most important optical exchange factors at each time step and the other exchange factors only a few times a day strongly reduces the computation time without any significant precision lost. With this solution, the computation time increases proportionally to the number N of the vertical layers and no longer proportionally to its square [N.sup.2]. Some specific points, such as numerical instabilities that may appear in the high atmosphere and errors that may be introduced if inappropriate treatments are performed when reflection at the surface occurs, are also investigated.

Published
2005

5. Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability?

Author

Oerder, Vera, Colas, François, Echevin, Vincent, Masson, Sebastien, Hourdin, Christophe, Jullien, Swen, Madec, Gurvan, Lemarie, Florian, Oerder, Vera, Colas, François, Echevin, Vincent, Masson, Sebastien, Hourdin, Christophe, Jullien, Swen, Madec, Gurvan, and Lemarie, Florian

Abstract

Satellite observations and a high-resolution regional ocean–atmosphere coupled model are used to study the air/sea interactions at the oceanic mesoscale in the Peru–Chile upwelling current system. Coupling between mesoscale sea surface temperature (SST) and wind stress (WS) intensity is evidenced and characterized by correlations and regression coefficients. Both the model and the observations display similar spatial and seasonal variability of the coupling characteristics that are stronger off Peru than off Northern Chile, in relation with stronger wind mean speed and steadiness. The coupling is also more intense during winter than during summer in both regions. It is shown that WS intensity anomalies due to SST anomalies are mainly forced by mixing coefficient anomalies and partially compensated by wind shear anomalies. A momentum balance analysis shows that wind speed anomalies are created by stress shear anomalies. Near-surface pressure gradient anomalies have a negligible contribution because of the back-pressure effect related to the air temperature inversion. As mixing coefficients are mainly unchanged between summer and winter, the stronger coupling in winter is due to the enhanced large-scale wind shear that enables a more efficient action of the turbulent stress perturbations. This mechanism is robust as it does not depend on the choice of planetary boundary layer parameterization.

Published
2016
Full Text
View/download PDF

6. Mesoscale ocean-atmosphere coupling in the Peru-Chile upwelling system

Author

Oerder, Véra, Colas, François, Echevin, Vincent, Masson, Sébastien, Hourdin, Christophe, Lemarié, Florian, Madec, Gurvan, Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Nucleus for European Modeling of the Ocean (NEMO R&D ), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Modelling, Observations, Identification for Environmental Sciences (MOISE), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire Jean Kuntzmann (LJK), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Laboratoire Jean Kuntzmann (LJK), Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Joseph Fourier - Grenoble 1 (UJF)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Inria Grenoble - Rhône-Alpes, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Physics::Atmospheric and Oceanic Physics
Abstract

International audience; Understanding the dynamics of Eastern boundary upwelling systems such as the Peru-Chile region is of major interest as these regions host an intense biological activity and productive fisheries. Moreover, they are generally poorly represented in global climate models due to biases in low cloud cover and a misrepresentation of mesoscale processes. The mesoscale activity of these systems has been studied quite extensively with observations and with ocean models which generally do not take into account the feedback of the ocean mesoscale (eddies, filaments and fronts) on the atmospheric forcing. However it has been evidenced that oceanic thermal gradients associated with oceanic eddies induce an atmospheric response, in particular in the surface wind, which is the main forcing in upwelling systems. As a consequence, the Humboldt current system appears to be a fully coupled system in which mesoscale air-sea interactions are to be taken into account. Using a regional coupled model (WRF-NEMO) at ~9 km resolution, we study the interactions between wind stress and sea surface temperature (SST) mesoscale structures in the Peru region. The relevant coupling scales are isolated and the spatial and temporal variations of these interactions are characterized. Correlations between mesoscale wind stress and SST compare well with results from satellite data when model fields are smoothed on the observations grid (~50 km), while model small-scale structures (at ~10km resolution) are more strongly coupled. The large-scale wind intensity and steadiness modulate the coupling intensity spatially and at seasonal time scales. The physical mechanisms of the atmosphere response to an SST gradient are also investigated, including the role of the sea surface oceanic current.

Published
2014

9. Les modèles climatiques gagnent en précision

Author

Masson, Sébastien, Hourdin, Christophe, Benshila, Rachid, Maisonnave, Éric, Meurdesoif, Yann, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), CERFACS, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ANR-11-MONU-0010,PULSATION,Simulation multi-échelle couplée océan-atmosphère sur calculateur peta scale(2011), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2012

10. Tropical Channel NEMO-OASIS-WRF Coupled Simulations at Very High Resolution

Author

Masson, Sébastien, Hourdin, Christophe, Benshila, Rachid, Maisonnave, Éric, Meurdesoif, Yann, Mazauric, Cyril, Samson, Guillaume, Colas, François, Madec, Gurvan, Bourdallé-Badie, Romain, Valcke, Sophie, Coquart, Laure, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Mercator Océan, Société Civile CNRS Ifremer IRD Météo-France SHOM, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), NCAR, ANR-11-MONU-0010,PULSATION,Simulation multi-échelle couplée océan-atmosphère sur calculateur peta scale(2011), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), CERFACS, and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)

Subjects
[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2012

13. A climate database for Mars

Author

Lewis, Stephen R., primary, Collins, Matthew, additional, Read, Peter L., additional, Forget, François, additional, Hourdin, Frédéric, additional, Fournier, Richard, additional, Hourdin, Christophe, additional, Talagrand, Olivier, additional, and Huot, Jean-Paul, additional

Published
1999
Full Text
View/download PDF

14. Net Exchange Reformulation of Radiative Transfer in the CO2 15-μm Band on Mars.

Author

Dufresne, Jean-Louis, Fournier, Richard, Hourdin, Christophe, and Hourdin, Frédéric

Subjects
RADIATIVE transfer, ASTROPHYSICS, GEOPHYSICS, RADIATION, MARS (Planet)
Abstract

The net exchange formulation (NEF) is an alternative to the usual radiative transfer formulation. It was proposed by two authors in 1967, but until now, this formulation has been used only in a very few cases for atmospheric studies. The aim of this paper is to present the NEF and its main advantages and to illustrate them in the case of planet Mars. In the NEF, the radiative fluxes are no longer considered. The basic variables are the net exchange rates between each pair of atmospheric layers i, j. NEF offers a meaningful matrix representation of radiative exchanges, allows qualification of the dominant contributions to the local heating rates, and provides a general framework to develop approximations satisfying reciprocity of radiative transfer as well as the first and second principles of thermodynamics. This may be very useful to develop fast radiative codes for GCMs. A radiative code developed along those lines is presented for a GCM of Mars. It is shown that computing the most important optical exchange factors at each time step and the other exchange factors only a few times a day strongly reduces the computation time without any significant precision lost. With this solution, the computation time increases proportionally to the number N of the vertical layers and no longer proportionally to its square N 2. Some specific points, such as numerical instabilities that may appear in the high atmosphere and errors that may be introduced if inappropriate treatments are performed when reflection at the surface occurs, are also investigated. [ABSTRACT FROM AUTHOR]

Published
2005
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results