TY - GEN A1 - Weiher, Stefan A1 - Akhtar, Naveed A1 - Brauch, Jennifer A1 - Breil, Marcus A1 - Davin, Edouard A1 - Ho-Hagemann, Ha T. M. A1 - Maisonnave, Eric A1 - Thürkow, Markus A1 - Will, Andreas T1 - Coupling of the regional climate model COSMO-CLM using OASIS3-MCT with regional ocean, land surface or global atmosphere model: description and performance T2 - Geoscientific Model Development N2 - We present the prototype of a regional climate system model based on the COSMO-CLM regional climate model coupled with several model components, analyze the performance of the couplings and present a strategy to find an optimum configuration with respect to computational costs and time to solution. The OASIS3-MCT coupler is used to couple COSMO-CLM with two land surface models (CLM and VEG3D), a regional ocean model for the Mediterranean Sea (NEMO-MED12), two ocean models for the North and Baltic Sea (NEMO-NORDIC and TRIMNP+CICE) and the atmospheric component of an earth system model (MPI-ESM). We present a unified OASIS3-MCT interface which handles all couplings in a similar way, minimizes the model source code modifications and describes the physics and numerics of the couplings. Furthermore, we discuss solutions for specific regional coupling problems like handling of different domains, multiple usage of MCT interpolation library and efficient exchange of 3D fields. A series of real-case simulations over Europe has been conducted and the computational performance of the couplings has been analyzed. The usage of the LUCIA tool of the OASIS3-MCT coupler enabled separation of the direct costs of: coupling, load imbalance and additional computations. The resulting limits for time to solution and costs are shown and the potential of further improvement of the computational efficiency is summarized for each coupling. It was found that the OASIS3-MCT coupler keeps the direct coupling costs of communication and horizontal interpolation small in comparison with the costs of the additional computations and load imbalance for all investigated couplings. For the first time this could be demonstrated for an exchange of approximately 450 2D fields per time step necessary for the atmosphere-atmosphere coupling between COSMO-CLM and MPI-ESM. A procedure for finding an optimum configuration for each of the couplings was developed considering the time to solution and costs of the simulations. The optimum configurations are presented for sequential and concurrent coupling layouts. The procedure applied can be regarded as independent on the specific coupling layout and coupling details. KW - Climate KW - Regional Climate Model KW - Regional Climate System Model KW - OASIS KW - Coupling KW - Performance KW - Parallelisation KW - Computational Efficiency KW - COSMO-CLM Y1 - 2016 U6 - https://doi.org/10.5194/gmd-2016-47 SN - 1991-9603 N1 - Discussion Paper VL - 47 SP - 1 EP - 61 ER - TY - GEN A1 - Davin, Edouard A1 - Rechid, Diana A1 - Breil, Marcus A1 - Cardoso, Rita M. A1 - Coppola, Erika A1 - Hoffmann, Peter A1 - Jach, Lisa L. A1 - Katragkou, Eleni A1 - Noblet-Ducoudré, Nathalie de A1 - Radtke, Kai A1 - Raffa, Mario A1 - Soares, Pedro A1 - Sofiadis, Giannis A1 - Strada, Susanna A1 - Strandberg, Gustav A1 - Tölle, Merja H. A1 - Warrach-Sagi, Kirsten A1 - Wulfmeyer, Volker T1 - Biogeophysical impacts of deforestation in Europe First results from the LUCAS Regional Climate Mode intercomparison T2 - Earth System Dynamics N2 - The Land Use and Climate Across Scales Flagship Pilot Study (LUCAS FPS) is a coordinated community effort to improve the integration of land use change (LUC) in regional climate models (RCMs) and to quantify the biogeophysical effects of LUC on local to regional climate in Europe. In the first phase of LUCAS, nine RCMs are used to explore the biogeophysical impacts of re-/afforestation over Europe: two idealized experiments representing respectively a non-forested and a maximally forested Europe are compared in order to quantify spatial and temporal variations in the regional climate sensitivity to forestation. We find some robust features in the simulated response to forestation. In particular, all models indicate a year-round decrease in surface albedo, which is most pronounced in winter and spring at high latitudes. This results in a winter warming effect, with values ranging from +0.2 to +1 K on average over Scandinavia depending on models. However, there are also a number of strongly diverging responses. For instance, there is no agreement on the sign of temperature changes in summer with some RCMs predicting a widespread cooling from forestation (well below −2 K in most regions), a widespread warming (around +2 K or above in most regions) or a mixed response. A large part of the inter-model spread is attributed to the representation of land processes. In particular, differences in the partitioning of sensible and latent heat are identified as a key source of uncertainty in summer. Atmospheric processes, such as changes in incoming radiation due to cloud cover feedbacks, also influence the simulated response in most seasons. In conclusion, the multi-model approach we use here has the potential to deliver more robust and reliable information to stakeholders involved in land use planning, as compared to results based on single models. However, given the contradictory responses identified, our results also show that there are still fundamental uncertainties that need to be tackled to better anticipate the possible intended or unintended consequences of LUC on regional climates. Y1 - 2020 U6 - https://doi.org/10.5194/esd-11-183-2020 SN - 2190-4995 VL - 11 IS - 1 SP - 183 EP - 200 ER -