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

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6. Performance et parallélisation

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Modélisation de composés moléculaires magnétiques et études de structures magnétiques non uniformes

BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

6. Performance et parallélisation

La puissance de calcul est la clef de voûte de la modélisation du climat. Depuis l’origine, cette science a suivi les progrès de l’informatique et en a largement bénéficié. Symétriquement, en tant qu’utilisatrice des supercalculateurs les plus puissants au monde, elle a longtemps contribué à leur développement. Tirer parti de toutes les ressources de calcul disponibles est donc une préoccupation majeure qui transparaît dans le code informatique lui-même : choix du langage, performance des alg..

La modélisation du climat: défis et opportunités

International audienceUsages 18-Le numérique de puissance Les voix de la recherche-#73-Clefs Recherche fondamentale Usages Clefs-#73-Les voix de la recherche Le numérique de puissance-1

Conservative interpolation between general spherical meshes

International audienceAn efficient, local, explicit, second-order, conservative interpolation algorithm between spherical meshes is presented. The cells composing the source and target meshes may be either spherical polygons or latitude–longitude quadrilaterals. Second-order accuracy is obtained by piece-wise linear finite-volume reconstruction over the source mesh. Global conservation is achieved through the introduction of a supermesh, whose cells are all possible intersections of source and target cells. Areas and intersections are computed exactly to yield a geometrically exact method. The main efficiency bottleneck caused by the construction of the supermesh is overcome by adopting tree-based data structures and algorithms, from which the mesh connectivity can also be deduced efficiently.The theoretical second-order accuracy is verified using a smooth test function and pairs of meshes commonly used for atmospheric modelling. Experiments confirm that the most expensive operations, especially the supermesh construction, have O(NlogN) computational cost. The method presented is meant to be incorporated in pre- or post-processing atmospheric modelling pipelines, or directly into models for flexible input/output. It could also serve as a basis for conservative coupling between model components, e.g., atmosphere and ocean

ICOLMDZORINCA CO2 Transport GMD 2023

<p>Efforts to monitor the emissions and absorptions of atmospheric carbon dioxide (CO₂) over the globe and to understand their varying regional patterns with greater accuracy have intensified in recent years. This study evaluates the performance of a new model coupling, ICOLMDZORINCA, built around the Laboratoire de Météorologie Dynamique atmospheric general circulation model (LMDZ) for simulating CO₂ transport. ICOLMDZORINCA utilizes the new icosahedral hydrostatic dynamical core called Dynamico running on an unstructured grid, which enables potential improvements in spatial resolution at the Equator while removing artificial distortions and numerical filters at the poles. Comparisons with a reference configuration using a structured latitude-longitude grid reveal that ICOLMDZORINCA well captures seasonal variations in CO₂ concentrations at surface stations. While not significantly enhancing the capture of complex seasonal patterns, ICOLMDZORINCA maintains comparable accuracy. Both configurations exhibit similar vertical CO₂ concentration profiles and display a consistent bias in the lower stratosphere relative to observational data. ICOLMDZORINCA demonstrates advantages in computational efficiency and storage, thanks to its reduced cell count per level and a homogeneous grid structure. It holds promise for future developments, including with the LMDZ offline model and associated inversion system, which contribute to the Copernicus Atmosphere Monitoring Service. Overall, the ICOLMDZORINCA configuration showcases the efficacy of utilizing an unstructured grid for the physics, and the capability of Dynamico in accurately simulating CO₂ transport. This study emphasizes the importance of advanced modeling approaches and high-resolution innovative grids in enhancing our understanding of the global carbon cycle and refining climate models.</p&gt

Les modèles climatiques gagnent en précision

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Tropical cyclones in global high-resolution simulations using the IPSL model

International audienceAbstract Despite many years of extensive research, the evolution of Tropical Cyclone (TC) activity in our changing climate remains uncertain. This is partly because the answer to that question relies primarily on climate simulations with horizontal resolutions of a few tens of kilometers. Such simulations have only recently become accessible for most modeling centers, including the Institut Pierre-Simon Laplace (IPSL). Using recent numerical developments in the IPSL model, we perform a series of historical atmospheric-only simulations that follow the HighResMIP protocol. We assess the impact of increasing the resolution from $${\sim }\, 200$$ ∼ 200 to 25 km on TC activity. In agreement with previous work, we find a systematic improvement of TC activity with increasing resolution with respect to the observations. However, a clear signature of TC frequencies convergence with resolution is still lacking. Cyclogenesis geographical distributions also improve at the scale of individual basins. This is particularly true of the North Atlantic, where the agreement with the observed distribution is impressive at 25 km. In agreement with the observations, TC activity correlates with the large-scale environment and ENSO in that basin. By contrast, TC frequencies remain too small in the Western North Pacific at 25 km, where significant biases of humidity and vorticity are found compared to the reanalysis. Despite the few minor weaknesses we identified, our results demonstrate that the IPSL model is a suitable tool for studying TCs on climate time scales. This work thus opens the way for further studies contributing to our understanding of TC climatology