Evaluation Report COSMO-CLM5.0

Abstract

The regional climate model COSMO-CLM is a community model (www.clm-community.com). In close collaboration with the COSMO-consortium the model is further developed by the community members for climate applications. One of the tasks of the community is to give a recommendation on the model version and to evaluate the models performance. The COPAT (Coordinated Parameter Testing) initiative is a voluntary community effort to carry out model simulations systematically by different institutions in order to test new model options and to find a satisfactory model setup for hydrostatic climate simulations over Europe. We will present the COPAT method used to achieve the latest recommended model version of COSMO-CLM (COSMO5.0_clm6). The simulations cover the EURO-CORDEX domain at two spatial resolutions 0.44° and 0.165°. They are forced by ERAinterim data for the time period of 1979-2000. Interpolated forcing data has been prepared once to ensure that all participating groups used identical forcing. The evaluation of each individual run has been performed for the time period 1981-2000 by using ETOOL and ETOOL-VIS. These tools have been developed within the community to evaluate standard COSMO-CLM output in comparison to observations provided by EOBS and CRU. The COPAT procedure was structured into 6 phases. In the Pre-Phase a group of institutions volunteered to contribute, a wiki has been setup, the forcing has been prepared and reference simulations at DKRZ have been performed. Furthermore, evaluation measures had been fixed and the necessary tools developed. In Phase 1 all participating institutions performed a reference run on their individual computing platforms and tested the influence of single model options on the results afterwards. Derived from the results of Phase 1 the most promising options were used in combinations in the second phase (Phase 2). These first two phases of COPAT consist of more than 70 simulations with a spatial resolution of 0.44°. Based on the best setup identified in Phase 2 a calibration of eight tuning parameters has been carried out following Bellbrat et al. (2012) in Phase 3. A final simulation with the calibrated parameters has been set up in Phase 4 at a higher resolution of 0.165°. The results were compared to previous model versions. The new model version COSMO5.0_clm6 led to the same or better results and therefore had been defined in the Final Phase as the new recommended model version of the community.