1. 1 RT3, Formulation of very high resolution Regional Climate Model Ensembles for Europe J.H. Christensen (DMI) M. Rummukainen (SMHI) B. van den Hurk (KNMI) DMI, SMHI, KNMI, ICTP, METO-HC, CNRM, GKSS, MPIMET, UCLM, INM, met.no, CUNI, CHMI

2. 2 Overall aim of RT3 RT3 has the responsibility for providing improved climate model tools developed in the context of regional models, but contributing to high-resolution modelling in general, first at spatial scales of 50 km at a European-wide scale within ENSEMBLES and later also at a resolution of 20km for specified sub-regions.

3. 3 RT3 links to other RTs (Output: specify need of GCM-data, to RT1/RT2A) Input: GCM data, from RT1/RT2A Input: Additional evaluation data, from RT5 Output: An RCM-ensemble system, to RT2B Input: RCM runs of GCM-”controls”, from RT2B (Input: impact study requirements, from RT6) Output: RCM climate change scenarios for a non- European region

4. 4 RT3 models and simulations DMI (HIRHAM), SMHI (RCA), KNMI (RACMO), ICTP (RegCM), METO-HC (HadRM), CNRM (ALADIN), GKSS (CLM), MPIMET (REMO), UCM (PROMES), INM (RCA or UM), met.no (HIRHAM), CUNI& CHMI (ALADIN) Regionalisation of ERA-40 at ~50 km (WP3.1) Regionalisation of ERA-40 at ~20 km (WP3.1) (GCM-driven RCM simulations done in RT2B) Simulations for a non-European region (WP3.5)

5. 5 RT3, Workpackages WP3.1: Creation of an RCM ensemble for ERA-40 WP3.2: Design and calibration of procedure to create probabilistic regional climate scenarios WP3.3: Design of ensemble strategy WP3.4: A comparative analysis of RCM ensemble simulations of present-day using GCM boundary conditions WP3.5: RCM-ensemble simulation for non-European areas

6. 6 RT3/WP3.1: RT3/WP3.1: Creation of an RCM ensemble for ERA-40 State-of-the-art RCM simulations at ~50km. Simulations with evaluated/improved RCMs at ~20 km. With some models, assess the role of land use and irrigation changes with experiments with and without such prescribed changes. (A possible link with RT7?) Link the evaluation of the simulations with RT5 activities, which will provide new high-resolution data- sets.

7. 7 RT3/WP3.2: RT3/WP3.2: Design and calibration of procedure to create probabilistic regional climate scenarios Techniques for generation of probabilistic regional scale predictions. (A regional counterpart to RT1 WP1.6.) Arrive at a basis for the weighting of individual ensemble members, to be further refined in WP3.4. Calculation of model weights will be introduced for the ensemble of models to be used in prediction mode, i.e. for use in RT2B.

8. 8 RT3/WP3.3: RT3/WP3.3: Design of ensemble strategy Design the strategy including selection of members based on (GCM) boundary conditions, and model formulation. Assign a desired number of RCM-GCM combinations to provide an "optimal" probabilistic future climate scenario, in collaboration with RT2a.

9. 9 RT3/WP3.4: RT3/WP3.4: A comparative analysis of RCM ensemble simulations of present- day using GCM boundary conditions Weighting procedure (WP3.2) based on ERA-40 driven RCMs applied to GCM-control driven RCMs Modifications to the procedure to account for GCM- biases developed to allow weighting for RCM downscaling GCM predictions Evaluation of the modified procedure Co-ordinating with RT2B, a strategy and size for the 20km RCM ensemble will be recommended

10. 10 RT3/WP3.5: RT3/WP3.5: RCM-ensemble simulation for non-European areas Objectives: Test RCMs for non-European regions, esp. tropics Study the effects of anthropogenic forcings (e.g. land use change, atmospheric aerosols) in tropical regions RCM climate change scenarios for a non-European region Possible regions: Sahel, equatorial Africa (West Africa, cf. AMMA), Amazon Basin, South Asia monsoon region Research steps: Perfect boundary condition experiments Sensitivity experiments (land-use change, aerosols) Scenario simulations