WP3.10 : Cross-assessment of CCI-ECVs over the Mediterranean domain Recent progresses: Extension of the confrontation with CCI-Sea level over the Mediterranean area : analysis of three coupled regional simulations (CNRM-RCSM, LMDZ-MED, MORCE-MED) and one Mediterranean Sea simulation (MED12) from the Med-Cordex multi-model ensemble. Communication of results at the 9th HyMeX Workshop, (Mykonos, 21-25 September, 2015). Submission of a publication entitled: « Improving the representation of Mediterranean sea level in regional climate models » (Adloff et al.).

Regional models over the Mediterranean domaine: the two CNRM models CNRM-RCSM4 MED12 Atmosphere Ocean Ocean ALADIN-Climat ALDERA* ORAS4 Corrected with the mean annual cycle of the CCI-ECV Sea Level COMBINE The CNRM-RCSM4 model is a regional climate system model coupling the atmospheric component ALADIN-Climat and the Mediterranean Sea component NEMOMED8 (resolution of 1/8°). The MED12 model is a new version of the NEMOMED Mediterranean sea model at a resolution of 1/12°. ALDERA results from the dynamical downscaling of ERA-interim usind the ALADIN-Climat model. The COMBINE ocean reanalysis used for the relaxation of the ocean component in the Atlantic buffer-zone doesn’t include satellite data assimilation. ORAS4 includes satellite data assimilation (AVISO) and is here corrected with the mean annual cycle of the CCI-ECV Sea Level over the 1993-2010 period (underestimated in ORAS4). NEMOMED8 NEMOMED12 Relaxation in the Atlantic buffer zone towards ocean reanalyses (COMBINE and corrected ORAS4)

Mean seasonal cycle of Mediterranean sea level over the period 1993-2010 (mm/yr) The ensemble of sea level datasets for comparison (grey shading labelled « OBS-REANA ») include: the CCI-ECV ; the ORAS4 global ocean reanalysis (Balmaseda et al., 2013) and two Mediterranean sea level reconstructions (Meyssignac et al., 2009; Calafat et al., 2011) 5 Adloff et al., 2016

Correlation between detrended time series and CCI_ECV 1993-2008 Correlation on detrended timeseries with CCI-ECV for the common period 1993-2008. Adloff et al., 2016

Trends of sea surface height anomalies over the period 1993-2010 (mm/yr) Trends of SSH anomalies over the 1993-2010 period (in mm/yr). Results from the RCSM4 model (top) are diagnosed from the free surface model calculation. They are compared with SSH CCI SSH (bottom). Adloff et al., 2016

WP3.10 : Cross-assessment of CCI-ECVs over the Mediterranean domain Some conclusions: The Mediterranean mean sea level is strongly influenced by the Atlantic conditions and thus the quality of the information in the lateral boundary conditions is crucial for the good modelling of Mediterranean sea level. The regional differences inside the basin that are induced by circulation changes are model-dependent and are not affected by the LBC. Correct Atlantic conditions from global circulation models should be used to project future Mediterranean sea level change. The error estimate of regional CCI sea level trends (3mm/year) seems overestimated.

WP3.10 : Cross-assessment of CCI-ECVs over the Mediterranean domain Future plans: Complete the analyse of the performances of the models by confronting the mean, the variability and the trends of a subset of variables inferred from the CCI-ECVs and from the simulations (Aerosols, soil moisture, SST) Analyse the consistency between different ECVs through the analysis of a climate specific event: possibly the 2006 heat wave.

WP4.1 : Exploiting CCI products in CMIP like experiments Recent progresses: Interaction with the science leader of the CCI-Sea ice consortium : an updated product will become available in 2016. At Météo-France we have performed AMIP-like simulations as part of sensitivity experiments to the L4 CCI-SST product (v1.0). These simulations are performed with Arpege-Climat v6 T127L91 (a version close to the one that will be used for CMIP6) and they consist in 5-member ensemble simulations with either the “recommended” AMIP forcing or a forcing where only SST is substituted with the CCI product (same sea ice). The covered period is1992-2010.

Seal level pressure in DJF averaged over the period 1992-2010 (hPa)

January 1992 (5 members per ensemble) Seal level pressure difference between the ensemble averaged of CCI and AMIP simulations (Pa) January 1992 (5 members per ensemble)

10% significance level (t-test) in January 1992 CCI-AMIP (5 members)

WP4.1 : Exploiting CCI products in CMIP like experiments Some preliminary conclusions: No systematic impact of the SST differences on the performance of the model for the simulation of the seasonal mean sea level pressure (comparison with ERA-Interim climatology). No significant impact on the simulated sea level pressure when considering the 5-member ensemble simulations over a specific month (t-test).

WP4.1 : Exploiting CCI products in CMIP like experiments Future plans: Complete and analyse the sensitivity experiments to SST-CCI. Perform new CMIP6 AMIP-like simulations with Arpege-Climat low and high resolution with CCI SST and sea-ice forcings : need for sea ice data. Analyse model simulations and compare results with those of the simulations performed by CMUG partners (similar simulations planned at LMD and SMHI this year).

Seal surface temperature difference between CCI and AMIP in January 1992 (°C) CCI-AMIP (5 members)