1. WP3.10 Cross-assessment of CCI-ECVs over the Mediterranean domain

2. WP3.10 : Cross-assessment of CCI-ECVs over the Mediterranean domain  Objective : Evaluate the performances (mean climate, variability and trends) of the Med-CORDEX regional climate system models over the Mediterranean domain with a sub-set of atmosphere, marine and surface CCI-ECVs. The consistency between CCI-ECVs will be analysed though the analysis of a climate specific event observed with the CCI-ECVs, observed in the atmosphere and/or marine reanalyses and possibly reproduced by at least one RCSM.  Scientific questions to be addressed : –Are the state of the art RCSMs able to reproduce observed Mediterranean climate trends and variability over the last decades ? –What are the potential coupled mechanisms between atmosphere, ocean and land that play a role on the characteristics of a climate specific event like a Mediterranean heat wave ?

3. The RCSM4 coupled regional model NEMOMED8 Regional version of NEMO-V2 with filtered free surface (Madec, 2008) Horizontal resolution 1/8°x1/8°cos(Φ), 43 vertical levels An Atlantic buffer zone (3D T-S and 2D SSH toward COMBINE reanalysis) ALADIN-Climat V5 Regional climate model (Colin et al., 2010) Horizontal resolution 50km, 31 vertical levels Spectral nudging (toward ERA-Interim reanalysis) TRIP River routing model (Oki and Sud, 1998; Decharme et al., 2010) 0.5° resolution of the river network OASIS coupler (Valcke, 2006)

4. Time series of mean sea level anomalies averaged over the Mediterranean Sea for the period 1980-2012 (m) Sevault et al., Tellus, 2014 mean thermosteric component included

5. Seasonal cycle of mean sea level anomaly over the Mediterranean Sea over the period 1993-2010 (cm) mean thermosteric component included (0-600m) Sevault et al., Tellus, 2014

6. The NEMOMED12 ocean regional model Gulf of Lions Adriatic Sea Buffer zone Gibraltar strait Sicily strait Ionian Sea Levantine Sea Egean Sea Otranto strait NEMOMED12 Regional version of NEMO-V3.2 with filtered free surface (Madec, 2008) Horizontal resolution 1/12°x1/12°cos(Φ), 75 vertical levels An Atlantic buffer zone: 3D T-S toward ORAS4 reanalysis (Balmaseda, 2013) and 2D SSH toward ORAS4 (assimilating AVISO SSH anomalies) with seasonal cycle from CCI-ECV Forced with ALADIN-Climat 12km constrained with ERA-Interim reanalysis Climatological rivers and black sea runoffs

7. Time series of mean sea level anomalies averaged over the Mediterranean Sea for the period 1980-2013 (m) (No mean thermosteric component) Adloff et al., in preparation (No mean thermosteric component)

8. Seasonal cycle of mean sea level anomaly over the Atlantic buffer zone over the period 1993-2010 (m) (No mean thermosteric component) Adloff et al., in preparation

9. Seasonal cycle of mean sea level anomaly over the Mediterranean Sea over the period 1993-2010 (m) (No mean thermosteric component) Adloff et al., in preparation

10. Trends of Mediterranean sea surface height anomalies over the period 1993-2010 mm/yr Adloff et al., in preparation

11. Conclusion  There is the need for an “SSH observation simulator” depending on the experimental protocol (mean trend and seasonal cycle): For RSCM4 simulation, SSH is relaxed in the Atlantic buffer zone toward COMBINE reanalysis that doesn’t assimilate satellite observations: a fairly good comparison of the simulated SSH with satellite-derived SSH over the Mediterranean basin is obtained by adding the simulated thermosteric component of sea level averaged over the basin. For NEMOMed12 simulation, the SSH in the Atlantic buffer zone is constrained to follow the CCI-ECV: a direct comparison of the simulated SSH with the satellite-derived SSH over the Mediterranean basin is adequate.

12. Conclusion  The boundary condition in the buffer zone of the Atlantic ocean is determinant for the reproduction of the mean sea level trend over the Mediterranean domain.  The Mediterranean model is able to reproduce the main pattern of sea level trend with local differences with the observations that are generally within the range of uncertainty of CCI sea level at the local scale (< 3mm/year). The coupling with the atmosphere has a small impact on this pattern.

13. Trends of sea surface height anomalies over the period 1993-2010 (mm/yr)