Sophie Valcke

The CNRM-CM5.1 global climate model: description and basic evaluation

A new version of the general circulation model CNRM-CM has been developed jointly by CNRM-GAME (Centre National de Recherches Météorologiques—Groupe d’études de l’Atmosphère Météorologique) and Cerfacs (Centre Européen de Recherche et de Formation Avancée) in order to contribute to phase 5 of the Coupled Model Intercomparison Project (CMIP5). The purpose of the study is to describe its main features and to provide a preliminary assessment of its mean climatology. CNRM-CM5.1 includes the atmospheric model ARPEGE-Climat (v5.2), the ocean model NEMO (v3.2), the land surface scheme ISBA and the sea ice model GELATO (v5) coupled through the OASIS (v3) system. The main improvements since CMIP3 are the following. Horizontal resolution has been increased both in the atmosphere (from 2.8° to 1.4°) and in the ocean (from 2° to 1°). The dynamical core of the atmospheric component has been revised. A new radiation scheme has been introduced and the treatments of tropospheric and stratospheric aerosols have been improved. Particular care has been devoted to ensure mass/water conservation in the atmospheric component. The land surface scheme ISBA has been externalised from the atmospheric model through the SURFEX platform and includes new developments such as a parameterization of sub-grid hydrology, a new freezing scheme and a new bulk parameterisation for ocean surface fluxes. The ocean model is based on the state-of-the-art version of NEMO, which has greatly progressed since the OPA8.0 version used in the CMIP3 version of CNRM-CM. Finally, the coupling between the different components through OASIS has also received a particular attention to avoid energy loss and spurious drifts. These developments generally lead to a more realistic representation of the mean recent climate and to a reduction of drifts in a preindustrial integration. The large-scale dynamics is generally improved both in the atmosphere and in the ocean, and the bias in mean surface temperature is clearly reduced. However, some flaws remain such as significant precipitation and radiative biases in many regions, or a pronounced drift in three dimensional salinity.

Simulation des changements climatiques au cours du XXIe siècle incluant l'ozone stratosphérique

Abstract Two climate simulations of 150 years, performed with a coupled ocean/sea-ice/atmosphere model including stratospheric ozone, respectively with and without heterogeneous chemistry, simulate the tropospheric warming associated with an increase of the greenhouse effect of carbon dioxide and other trace gases since 1950 and their impact on sea–ice extent, as well as the stratospheric cooling and its impact on ozone concentration. The scenario with heterogeneous chemistry reproduces the formation of the ozone hole over the South Pole from the 1970s and its deepening until the present time, and shows that the ozone hole should progressively fill during the coming decades. To cite this article: J.-F. Royer et al., C. R. Geoscience 334 (2002) 147–154.

Simulations couplées globales des changements climatiques associés à une augmentation de la teneur atmosphérique en CO2

Abstract Two transient CO 2 experiments using two coupled general circulation models developed by the French GASTON group have been realized using the same methodology. No flux corrections at the air-sea interface were used in these experiments. The main features of the present climate are reasonably well captured by both coupled models in the control simulations, although the biases are not the same, The transient CO 2 simulations show a global warming, ranging between 1.6 and 2.0 °C at the time of CO 2 doubling (+ 70 years). These values, and the main geographical characteristics of climate change, are in agreement with previous studies published by other research groups, using either flux corrected or non-flux corrected models.

A European Network for Earth System Modeling

The increasing complexity of Earth system models and the computing facilities needed to run those models put a heavy technical burden on research teams active in climate modeling. To ease this burden, a European collaborative venture called PRISM was initiated in December 2001 to organize a network of experts in order to share the development, maintenance, and support of Earth system modeling software tools and community standards. PRISM was recently reorganized, and a new Web portal (http://prism.enes.org) was unveiled in July 2006. The PRISM network was developed with the hope that advancing specific common standards and tools will reduce the technical development efforts of individual research teams, facilitate the assembling, running, and postprocessing of Earth system models based on state-of-the-art component models, and hence facilitate scientific collaboration between the different research groups in Europe and elsewhere.

Decadal prediction skill using a high-resolution climate model

The ability of a high-resolution coupled atmosphere–ocean general circulation model (with a horizontal resolution of a quarter of a degree in the ocean and of about 0.5° in the atmosphere) to predict the annual means of temperature, precipitation, sea-ice volume and extent is assessed based on initialized hindcasts over the 1993–2009 period. Significant skill in predicting sea surface temperatures is obtained, especially over the North Atlantic, the tropical Atlantic and the Indian Ocean. The Sea Ice Extent and volume are also reasonably predicted in winter (March) and summer (September). The model skill is mainly due to the external forcing associated with well-mixed greenhouse gases. A decrease in the global warming rate associated with a negative phase of the Pacific Decadal Oscillation is simulated by the model over a suite of 10-year periods when initialized from starting dates between 1999 and 2003. The model ability to predict regional change is investigated by focusing on the mid-90’s Atlantic Ocean subpolar gyre warming. The model simulates the North Atlantic warming associated with a meridional heat transport increase, a strengthening of the North Atlantic current and a deepening of the mixed layer over the Labrador Sea. The atmosphere plays a role in the warming through a modulation of the North Atlantic Oscillation: a negative sea level pressure anomaly, located south of the subpolar gyre is associated with a wind speed decrease over the subpolar gyre. This leads to a reduced oceanic heat-loss and favors a northward displacement of anomalously warm and salty subtropical water that both concur to the subpolar gyre warming. We finally conclude that the subpolar gyre warming is mainly triggered by ocean dynamics with a possible contribution of atmospheric circulation favoring its persistence.

Earth system modelling 3: Coupling software and strategies

Collected articles in this series are dedicated to the development and use of software for earth system modelling and aims at bridging the gap between IT solutions and climate science. The particular topic covered in this volume addresses the major coupling software developed and used in the climate modelling community.

Development and performance of a new version of the OASIS coupler, OASIS3-MCT_3.0

OASIS is coupling software developed primarily for use in the climate community. It provides 10 the ability to couple different models with low implementation and performance overhead. OASIS3-MCT is the latest version of OASIS. It includes several improvements compared to OASIS3 including elimination of a separate hub coupler process, parallelization of the coupling communication and run time grid interpolation, and the ability to easily reuse mapping weights files. OASIS3-MCT_3.0 is the latest release and includes the ability to couple between components running sequentially on the same set of tasks 15 as well as to couple within a single component between different grids or decompositions such as physics, dynamics, and I/O. OASIS3-MCT has been tested with different configurations on up to 32,000 processes, with components running on high-resolution grids with up to 1.5 million grid cells, and with over 10,000 two dimensional coupling fields. Several new features will be available in OASIS3-MCT_4.0 and some of those are also described. 20

The European PRISM Network

The increasing complexity of Earth system models and the computing facilities needed to run them put a heavy technical burden on the research teams active in climate modelling.

The OASIS Coupler

In 1991, CERFACS was commissioned by the French climate modelling community to perform the technical assembling of an ocean General Circulation Model (GCM), Ocean Parallelise (OPA) developed by the Laboratoire d’Oceanographie Dynamique et de Climatologie (LODYC), and two different atmospheric GCMs, Action de Recherche Petite Echelle Grande Echelle (ARPEGE) and the Laboratoire de Meteorologie Dynamique zoom (LMDz) model developed respectively by Meteo-France and the Laboratoire de Meteorologie Dynamique (LMD).

The PRISM Support Initiative, COSMOS and OASIS4

The increasing complexity of Earth System Models (ESMs) and computing facilities puts a heavy technical burden on the research teams active in climate modelling. The Partnership for Research Infrastructures in earth System Modelling (PRISM) provides the Earth System Modelling community with a forum to promote sharing of development, maintenance and support of standards and software tools used to assemble, run, and analyse ESMs based on state-of-the-art component models (ocean, atmosphere, land surface, etc..) developed in the different climate research centres in Europe and elsewhere. PRISM is organised as a distributed network of experts who contribute to five “PRISM Areas of Expertise” (PAE): (1) Code coupling and input/output, (2) Integration and modelling environments, (3) Data processing, visualisation and management, (4) Meta-data, and (5) Computing. Some of the tools and concepts developed within PRISM have been incorporated in the COmmunity Earth System MOdelS (COSMOS) project, like the PRISM Compile and Runtime Environment and the OASIS3 coupler. Within PRISM, further development is on-going: one example is the OASIS4 coupler, which targets the next generation of Earth system models.