Modelling Near Future Regional Climate Change for Germany and Africa

The scope of regional climate simulations carried out at the Institute for Meteorology and Climate Research (IMK) of Karlsruhe Institute of Technology (KIT) using the regional climate model (RCM) COSMO-CLM (CCLM) has been extended during the last years. From the focus first on Southwest Germany the area of interest has then been extended to the whole of Germany for the assessment of changes in flood risk for medium and small mountainous river catchments (CEDIM project: www.cedim.de ), and within the frame of CORDEX (Coordinated Regional climate Downscaling Experiment, http://wcrp.ipsl.jussieu.fr/SF_RCD_CORDEX.html ) also to the whole African continent. CORDEX aims to provide a framework to evaluate and benchmark RCMs and to design a set of experiments to produce climate projections for use in impact and adaption studies and as input to the IPCC 5th Assessment Report (AR5). Within the CEDIM-project “Flood hazard in a changing climate” an ensemble of 14 CCLM simulations have been created at the HLRS facilities. They have been driven by three realizations of the global ECHAM5 model and one realization of the Canadian model CGCM3, all using the A1B emission scenario. Although the ensemble spans a large range of values, there is a general pattern of increasing temperatures throughout the year, and also increases in precipitation for most of the year, except for summer when a decrease is more likely. Related to the NEC SX-8 an aggregated computing time of 1145 node-days have been needed for all simulations. The efforts within the CORDEX framework began with a series of sensitivity runs in order to identify a model configuration suitable for Africa. The simulations have been driven by ERA-Interim reanalysis. Based on the experiences gained from the sensitivity runs evaluation simulations have been carried out for the 20 years period from 1989 until 2008 for two different horizontal resolutions, 0.44 Deg and 0.22 Deg. The evaluation of the results is still in progress. However, first comparisons between the results of various RCMs, including CCLM, participating in the CORDEX project show a rather wide intra-model spread of the results, and also rather large discrepancies to climatic observations. The High Performance Computing (HPC) demands for the two simulations (0.44 Deg and 0.22 Deg) were 14 node-days and 86 node-days, respectively. Within KLIWA (Klimaveränderung und Wasserwirtschaft; www.kliwa.de ) a project has recently been initiated to assess the impact of climate change on soil erosion in Southern Germany. The work will focus on modelling extreme precipitation events at higher spatial and temporal resolution (2.8 km, 1 km; 1 hour, 5 minutes) for the recent past (ca. 1970–2000) and near future (2011–2050). The purpose is to evaluate what the added values of very high spatial and temporal resolution are and how the high resolution affects the precipitation statistics as well as the changes in erosion-related extreme precipitation events in the future. Further large demands for HPC will also be necessary within the program MIKLIP (Mittelfristige Klimaprognosen) initiated and recently approved by the Federal Ministry for Science and Education (BMBF). IMK will participate in joint projects which aim at regional decadal predictions of climate for Central Europe and the West African monsoon region.