Abstract
Feedback between the Mediterranean Sea and the atmosphere on various temporal and spatial scales plays a major role in the regional climate system. We studied the impact of horizontal atmospheric grid resolution (grid-spacing of ~9 vs. ~50 km) and dynamic ocean coupling (the ocean model NEMOMED12) in simulations with the regional climate model COSMO-CLM. The evaluation focused on sea surface heat fluxes, 10-m wind speed, and sea surface temperature (SST) parameters on both seasonal and annual timescales. The finer grid improved the wind speed (particularly near coastal areas) and subsequently the turbulent heat flux simulations. Both parameters were better simulated with the interactive ocean model NEMOMED12 than with prescribed daily ocean SSTs (using near-observation ERA-Interim reanalysis based SSTs), but coupling introduced a warm SST bias in winter. Radiation fluxes were slightly better represented in coarse-grid simulations. Still, only the higher-resolution coupled simulations could reproduce the observed net outgoing total heat flux over the Mediterranean Sea. Investigation of the impact of sub-diurnal SST variations showed a strong effect on sub-daily heat fluxes and wind speed but minor effects at longer time scales. Therefore, a coupled atmosphere–ocean climate model should be preferred for studying the Mediterranean Sea climate system. Higher-resolution models should be preferred, but they are not yet able to perform better than their coarse-resolution predecessors in all aspects.
Highlights
The semi-enclosed Mediterranean Sea, with its intricate coastline and topographic features, functions as a source of moisture and heat and has a substantial impact on local and remote climate conditions (Artale et al 2010)
We found that ocean coupling does not change the intensity of heat-waves, which is shown by Tomassini and Elizalde (2012)
The total mean difference (MD) and root mean square error (RMSE) of daily values of the respective seasons are used as simple statistical measures in the following discussions
Summary
The semi-enclosed Mediterranean Sea, with its intricate coastline and topographic features, functions as a source of moisture and heat and has a substantial impact on local and remote climate conditions (Artale et al 2010). Somot et al (2008) show that a high-resolution AORCM amplifies the climate change signal compared to an RCM in future projections in the Euro-Mediterranean region They explained this result based on better consistency among the SST, airsea fluxes, and vertical structure of the atmosphere in the AORCM. All the studies noted above used an atmospheric grid resolution in the range of 20–50 km to investigate the added value of ocean coupling over different timescales These studies show that even though the AORCMs improved the representation of air-sea fluxes over the Mediterranean Sea, large uncertainties still persist.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
