| ABSTRACT | Regional Climate System Models (RCSM) belong to the same family as the global earth system models (ESM) used in the CMIP experiments, but generally have a higher resolution. They allow to reproduce medium scale atmospheric and oceanic phenomena on periods going from present time hindcast to scenarios for the 21st century.
To compose this CNRM-RCSM6 model we chose the most recent versions of atmosphere and ocean models available at the CNRM, which are also used for CMIP experiments. The atmosphere model (ALADIN-Climate v6, with new atmospheric physics, 12 km resolution and 91 levels), the multi-surface model (SURFEX v8, new physics, 6-8 km resolution), the river routine model (CTRIP, with deep drainage and flood plains, but still a 50 km resolution), the inland model (FLAKE) are described in Voldoire et al. (2017). The ocean model is NEMOMED12 v3.6 (Beuvier et al. (2012), Hamon et al (2016) for the v3.2). OASIS3-MCT (Valcke et al. (2015)) is used at the coupler, at a 1h-frequency.
Besides we use new lateral boundary conditions compared to the previous CNRM-RCSM4 model0: a new climatology for the aerosols (Nabat et al. (2013)), ORAS4 ocean reanalysis (Balmaseda et al. (2013)) for the Atlantic part of the model, monthly fields in temperature and salinity, a new Sea Surface Height climatology for relaxation in the Atlantic part, composed by the ORAS4 monthly fields, with a corrected seasonal cycle which follows the one of CCI-ECV (Adloff et al. (2017)), a monthly climatology of the surface Chlorophyll concentration (2003-2011 ESA-CCI, T. Arsouze personal communication). Finally ERA-Interim reanalysis (Berrisford et al. (2009)) is used for the spectral nudging in the atmosphere, and for the Sea Surface Temperature outside the Mediterranean region.
After the description of the model, results for the 1980-2012 period will be presented and compared to observational datasets (oceanic and atmospheric data, river discharges). This first hindcast with CNRM-RCSM6 shows positive aspects like a realistic Aerosol Optical Depth trend on the period, and thus shortwave, latent heat and Sea Surface Temperature (SST) trends, a good simulation of SST and SSH, and realistic representation of the diurnal cycle of SST. Nevertheless one particular aspect to improve is the representation of the rivers runoffs, largely overestimated on the Black Sea drainage area, with consequences on the salinity, thermohaline circulation, and deep water convection. |