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7 results on '"Decharme, B."'

1. The Plumbing of Land Surface Models : Benchmarking Model Performance

Author

Best, M. J., Abramowitz, G., Johnson, H. R., Pitman, A. J., Balsamo, G., Boone, A., Cuntz, M., Decharme, B., Dirmeyer, P. A., Dong, J., Ek, M., Guo, Z., Haverd, V., van den Hurk, B. J. J., Nearing, G. S., Pak, B., Peters-Lidard, C., Santanello, J. A., Stevens, L., and Vuichard, N.

Published
2015

5. Tracking Changes in Climate Sensitivity in CNRM Climate Models.

Author

Saint‐Martin, D., Geoffroy, O., Voldoire, A., Cattiaux, J., Brient, F., Chauvin, F., Chevallier, M., Colin, J., Decharme, B., Delire, C., Douville, H., Guérémy, J.‐F., Joetzjer, E., Ribes, A., Roehrig, R., Terray, L., and Valcke, S.

Subjects
CLIMATE sensitivity, ATMOSPHERIC models, CLIMATE change, CLIMATE change models, GLOBAL temperature changes
Abstract

The equilibrium climate sensitivity (ECS) in the latest version of CNRM climate model, CNRM‐CM6‐1, and in its high‐resolution counterpart, CNRM‐CM6‐1‐HR, is significantly larger than in the previous version (CNRM‐CM5.1). The traceability of this climate sensitivity change is investigated using coupled ocean‐atmosphere model climate change simulations. These simulations show that the increase in ECS is the result of changes in the atmospheric component. A particular attention is paid to the method used to decompose the equilibrium temperature response difference, by using a linearized decomposition of the individual radiative agents diagnosed by a radiative kernel technique. The climate sensitivity increase is primarily due to the cloud radiative responses, with a predominant contribution of the tropical longwave response (including both feedback and forcing adjustment) and a significant contribution of the extratropical and tropical shortwave feedback changes. A series of stand‐alone atmosphere experiments is carried out to quantify the contributions of each atmospheric development to this difference between CNRM‐CM5.1 and CNRM‐CM6‐1. The change of the convection scheme appears to play an important role in driving the cloud changes, with a large effect on the tropical longwave cloud feedback change. Plain Language Summary: The global equilibrium temperature change in response to a doubling of the atmospheric carbon dioxide concentration is an important characteristic of the climate system known as the equilibrium climate sensitivity (ECS). Many climate models contributing to CMIP6 (Coupled Model Intercomparison Project phase 6) have a larger ECS than their CMIP5 predecessors. Here, we investigate the origins of this increase for the CNRM model and its high‐resolution version. We find that it primarily results from changes in the atmospheric component, in particular in the convection scheme, through its impact on the cloud radiative responses. Key Points: The CNRM climate models contributing to Coupled Model Intercomparison Project phase 6 have a larger climate sensitivity than their CMIP5 predecessorThe climate sensitivity increase is the result of changes in the atmospheric component, through the dominant role of tropical cloud changesThe new convection scheme appears to play an important role in driving the cloud changes [ABSTRACT FROM AUTHOR]

Published
2021
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6. The Plumbing of Land Surface Models: Benchmarking Model Performance

Author

Vuichard, And, Best, M., Abramowitz, G., Johnson, H., Pitman, A., Balsamo, G., Boone, A., Cuntz, M., Decharme, B., Dirmeyer, P., Dong, J., EK, M., Guo, Z., Haverd, V., Van Den Hurk, B., Nearing, G., Pak, B., Peters-Lidard, C., Santanello, J., Stevens, L., Vuichard, N., Department Computational Hydrosystems [UFZ Leipzig], Helmholtz Centre for Environmental Research (UFZ), Joint DECC/Defra Met Office Hadley Centre Climate Programme CA01101Australian Research CouncilCE110001028United States Department of Energy (DOE)DE-FG02-04ER63917DE-FG02-04ER63911CFCAS Natural Sciences and Engineering Research Council of Canada (NSERC) BIOCAP CGIAR Natural Resources Canada European Commission FAO-GTOS-TCO iLEAPS Max Planck Institute for Biogeochemistry National Science Foundation (NSF) Tuscia University Universite Laval and Environment Canada United States Department of Energy (DOE, United Kingdom Met Office [Exeter], University of New South Wales [Sydney] (UNSW), European Centre for Medium-Range Weather Forecasts (ECMWF), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), George Mason University [Fairfax], Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), NASA Goddard Space Flight Center (GSFC), GSFC Hydrospheric and Biospheric Sciences Laboratory, 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), Modélisation des Surfaces et Interfaces Continentales (MOSAIC), 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)-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), Water and Climate Risk, Amsterdam Global Change Institute, Météo France-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), 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)-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), Climate Change Research Centre [Sydney] (CCRC), Météo France-Centre National de la Recherche Scientifique (CNRS), and Royal Netherlands Meteorological Institute (KNMI)

Subjects
Surface (mathematics), Atmospheric Science, Meteorology, Climate Models, Parameterization, Project, Sensible heat, [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Latent heat, Range (statistics), Energy partitioning, Shortwave radiation, SDG 7 - Affordable and Clean Energy, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, Energy, Water, Model comparison, Benchmarking, Model evaluation/performance, Impact, Phase, [SDE]Environmental Sciences, Environmental science, Soil-moisture, Land surface model, Hydrology, Atmosphere Coupling Experiment, Nonlinear regression, Simulation
Abstract

The Protocol for the Analysis of Land Surface Models (PALS) Land Surface Model Benchmarking Evaluation Project (PLUMBER) was designed to be a land surface model (LSM) benchmarking intercomparison. Unlike the traditional methods of LSM evaluation or comparison, benchmarking uses a fundamentally different approach in that it sets expectations of performance in a range of metrics a priori—before model simulations are performed. This can lead to very different conclusions about LSM performance. For this study, both simple physically based models and empirical relationships were used as the benchmarks. Simulations were performed with 13 LSMs using atmospheric forcing for 20 sites, and then model performance relative to these benchmarks was examined. Results show that even for commonly used statistical metrics, the LSMs’ performance varies considerably when compared to the different benchmarks. All models outperform the simple physically based benchmarks, but for sensible heat flux the LSMs are themselves outperformed by an out-of-sample linear regression against downward shortwave radiation. While moisture information is clearly central to latent heat flux prediction, the LSMs are still outperformed by a three-variable nonlinear regression that uses instantaneous atmospheric humidity and temperature in addition to downward shortwave radiation. These results highlight the limitations of the prevailing paradigm of LSM evaluation that simply compares an LSM to observations and to other LSMs without a mechanism to objectively quantify the expectations of performance. The authors conclude that their results challenge the conceptual view of energy partitioning at the land surface.

Published
2015

7. Fast‐Forward to Perturbed Equilibrium Climate.

Author

Saint‐Martin, D., Geoffroy, O., Watson, L., Douville, H., Bellon, G., Voldoire, A., Cattiaux, J., Decharme, B., and Ribes, A.

Subjects
CLIMATE sensitivity, ATMOSPHERIC models, CLIMATOLOGY, CLIMATE change, EQUILIBRIUM, CARBON dioxide
Abstract

The equilibrium climate sensitivity, that is, the global‐mean surface‐air temperature change in response to a doubling of the carbon dioxide concentration is a widely used metric in climate change studies. Its exact value is rarely known because its estimation requires a long integration time of several thousand years. We propose a method to estimate an accurate value of the equilibrium response from fully coupled climate models at a reasonable computational cost. Using this method, our state‐of‐the‐art climate model CNRM‐CM6‐1 reaches a stationary state after only few hundred of years of integration. This "Fast‐Forward" method consists of an optimal two‐step forcing pathway designed using the framework of a two‐layer energy balance model. It can be applied easily to any coupled climate model. Key Points: A simple method for estimating the equilibrium climate sensitivity is proposedThe method allows to simulate the stationary climate corresponding to any given radiative perturbation with a limited computational costThe method can be applied to any atmosphere‐ocean coupled climate model [ABSTRACT FROM AUTHOR]

Published
2019
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