The Copernicus Mediterranean Forecasting Systems: description and quality assessment of recent evolutions

The Mediterranean Monitoring and Forecasting Center (Med-MFC) of the Copernicus Marine Service provides operational, regular, and systematic reference information on both the blue state (physical oceanography and waves) and the green state (biogeochemistry) of the Mediterranean Sea.

Relying on state-of-the-art modeling and data assimilation systems ingesting in-situ and satellite observations, Med-MFC delivers Near Real Time (NRT) analyses, short-term forecasts up to 10 days, as well as consistent Multi-Year reanalyses and interim extensions at a horizontal resolution of about 4 km.

This contribution presents a detailed description and quality assessment of the most recent modeling upgrades that have been implemented in the latest operational systems since November 2025.

In particular, the major modelling advancements for each system component are as provided hereafter.

The physical NRT operational system has been improved by implementing: (1) updated open lateral boundary conditions in the Dardanelles Strait to enhance the connection with the Black Sea through a high resolution Marmara Sea model; (2) a revised and updated data assimilation model, OceanVar2, which now includes a barotropic model operator for SLA assimilation and a diffuse filter operator; (3) a forecasts initialization with analysis fields on a daily basis, rather than once a week as in the previous version.

The wave NRT operational system has been improved by including wind speed satellite observations in the data assimilation module. In this way, the ECMWF analysis winds used to drive the system, are updated to support the corrections introduced by the assimilation of Significant Wave Height observations (SWH). The complete validation against in-situ and satellite observations included SWH, maximum wave height, and mean wave period, all maintaining the good quality of the previous Med-WAV NRT system version.

The Biogeochemical NRT operational system has been enhanced by: (1) improving the BFM (Biogrochemical Flux Model) with revised carbon-oxygen parameterization and  optimization for phytoplankton phenology; (2) using of 6-hours averaged (rather than daily) forcing for transport and ocean physics from the physical NRT system; (3) using Nitrogen and Phosphate air deposition from CAMS and literature instead of a constant value, and (4) using daily terrestrial loads of nutrients and carbon based on freshwater inflow provided by the Copernicus Emergency Service EFAS (European Flood Awareness System) dataset.

The model evolutions have been extensively qualified by comparing model results from a series of sensitivity numerical experiments with respect to best available satellite and in-situ observations in order to provide a reliable validation assessment. Based on the principle of continuous improvement, each evolution has contributed, albeit to different extents, to improve the quality of the delivered variables in the Copernicus Mediterranean NRT products, as evidenced by reduced error and bias relative to the previous versions.