GOFS16: an operational global ocean analysis and forecasting system at eddy-resolving resolution

Abstract. The Global Ocean Forecast System GOFS16 is an operational ocean analysis and forecast system that has been running daily at the Euro-Mediterranean Center on Climate Change since early 2017. GOFS16 produces 6-day forecasts of the state of the global ocean and sea ice (three-dimensional ocean temperature, salinity, and currents, as well as sea level, sea ice thickness, concentration and drift) with a system based on the NEMO model configured in a global eddying ocean at 1/16° horizontal resolution and 98 vertical levels. To compute the initial conditions for the forecasting, in situ observations of temperature and salinity, altimeter data of sea level anomaly and satellite sea surface temperature fields are jointly assimilated each day over a 1-day observation window with a 3DVar scheme, OceanVar, adapted to handle the global high-resolution grid. This paper introduces the first version of the GOFS16 system and describes its components and the validation procedure, which routinely produces statistics of the system skill. The scientific assessment is presented for the period January 2022–December 2023, at global and regional scales. Results indicate that GOFS16 performs within the expected range of skill for current global systems. However, the impact of the eddy-resolving resolution is hidden either by system weaknesses or traditional verification metrics not adequate at such resolution.