Modeling the impact of thin scales on the circulation in the Mediterranean

The group SIROCCO LA was one of the winners of the “mesochallenge” launched by the mesocentre CALMIP to test the new supercomputer OLYMPE (1,365 Petaflop / s, 13464 cores of calculations, 76 TB of memory). The challenge was to use a significant portion (up to 12960 calculation cores) of the OLYMPE computing system to deal with an ambitious scientific problem. Thanks to the collaboration with CALMIP engineers, engineers and researchers of SIROCCO have been able to realize with the latest version of the model SYMPHONIE (with a new vertical coordinate), a simulation of more than one year of the whole of the Mediterranean at 500 m horizontal resolution is about 500 million calculation points! This simulation is going to be used to analyze the processes of fine scale (<10 km) in the different regions of the Mediterranean basin and to understand their role on the circulation on a larger scale.

The figure shows a zoom of the Mediterranean grid on the Levantina basin (see position in the box). On the left, the winter surface temperature shows a cold zone (RG) known as the Gyre de Rhodes, which is the place of formation of intermediate Levantine waters. It is surrounded by hot water organized in semi-permanent semi-permanent mesoscale eddies like that of Iera-Petra (IE) of 80 kilometers in diameter. On the right is the vorticity of the surface current normalized by planetary vorticity. The vortices are in blue (negative vorticity). Between vortices, vorticity is organized in submersoscale filaments of typical width 4 kilometers dominated by cyclonic structures (red). The role of these small scales will be at the center of the projected analysis.

(a) the Levantine Basin is the framework of the international PERLE experiment (2018-2019) on the formation of Levantine waters.