CLIMB Climate Induced Changes on the Hydrology of Mediterranean Basins - Reducing Uncertainty and Quantifying Risk through an Integrated Monitoring and Modeling System (1.st internal report of CRS4-WP4: Climate Models Auditing and Downscaling , June 2010)  2010 by CRS4 PRELIMINARY RESULTS ON THE VERIFICATION OF THE WATER BALANCE ASPECTS OF THE REGCM3 REGIONAL CLIMATE MODEL ON YEARLY SCALES. M. Marrocu and G. Pusceddu CRS4, Loc. Piscina Manna, Edificio 1 - 09010 Pula (CA - Italy) ABSTRACT In this report some preliminary results obtained implementing the RegCM3 regional climate model to downscale, at the relatively high horizontal spatial resolution of about 25km, one year (the 1982) of the ECMWF ERA40 reanalysis in the Western Europe and Mediterranean area, are discussed. The main aim of this work is to assess the performance of the RegCM3 describing the runoff (R), the precipitation (P) and the evapotranspiration (E) components of the hydrological budget. This has been made comparing the monthly precipitation averages for 1982 against a gridded dataset, at spatial resolution of 0.5°, of measured data (CRU dataset) and then checking physical consistency of the simulated P field with the corresponding R and E fields. 1 INTRODUCTION One of the objectives of the WP4 1 , of the CLIMB project, is to implement robust procedures of intercomparison and verification (auditing) to evaluate reliability of the output of different climate models. 1 A complete description, extracted from the final CLIMB project proposal Description of Work (DoW), of the objectives of the WP4 can be found in the Appendix A.