The ENEA-REG system (v1.0), a multi-component regional earth system model. Sensitivity to different atmospheric component over Med-CORDEX region

Abstract. In this study, a new regional Earth system model is developed and applied to the Med-CORDEX region. The ENEA-REG system is made up of two interchangeable regional climate models as atmospheric components (RegCM and WRF), a river model (HD), and an ocean model (MITgcm); processes taking place at the land surface are represented within the atmospheric models with the possibility to use several land surface schemes of different complexity. The coupling between these components is performed through the RegESM driver. Here, we present and describe our regional Earth system model and evaluate its components using a multidecadal hindcast simulation over the period 1980–2013 driven by ERA-INTERIM reanalysis. We show how the atmospheric components are able to correctly reproduce both large-scale and local features of the Euro-Mediterranean climate, although some remarkable biases are relevant for some variables. In particular, WRF has a significant cold bias during winter over North-Eastern bound of the domain, while RegCM systematically overestimates the wind speed over the Mediterranean Sea. This latter bias has severe consequences on the ocean component: we show that when WRF is used as the atmospheric component of the Earth system, the performances of the ocean model are remarkably better compared with the RegCM version. Our regional Earth system model allows studying the Euro-Mediterranean climate system and can be applied to both hindcast and scenario simulations.