WP3.10Cross-assessment of CCI-ECVs over the

Mediterranean domain

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 ?

The RCSM4 coupled regional model

NEMOMED8Regional version of NEMO-V2 with

filtered free surface (Madec, 2008)Horizontal resolution 1/8°x1/8°cos(Φ),

43 vertical levelsAn Atlantic buffer zone (3D T-S and 2D

SSH toward COMBINE reanalysis)

ALADIN-Climat V5Regional climate model (Colin et al.,

2010)

Horizontal resolution 50km, 31 vertical levels

Spectral nudging (toward ERA-Interim reanalysis)

TRIPRiver routing model (Oki and Sud, 1998; Decharme et al., 2010)

0.5° resolution of the river network

OASIS coupler (Valcke, 2006)

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 mean thermosteric component included

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

The NEMOMED12 ocean regional model

Gulf of Lions

Adriatic Sea

Buffer zone

Gibraltar strait

Sicily strait

Ionian SeaLevantine

Sea

Egean Sea

Otranto strait

NEMOMED12Regional version of NEMO-V3.2 with filtered free surface (Madec, 2008)Horizontal resolution 1/12°x1/12°cos(Φ), 75 vertical levelsAn 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 reanalysisClimatological rivers and black sea runoffs

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)

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

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

Trends of Mediterranean sea surface height anomalies over the period 1993-2010

mm/yr

Adloff et al., in preparation

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.

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.

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