GOFS16: A Global Ocean-Sea Ice Forecast System at Eddying Resolution

An operational system to forecast the state of the global ocean has been developed and implemented at CMCC over the last 6 years, and runs daily since July 2017. The system, known as GOFS16, consists of a global ocean/sea ice configurations at 1/16° horizontal resolution of (∼7km at the equator and ∼3km at high latitudes) with 98 unevenly-spaced vertical levels, that makes it one of the few mesoscale-resolving global operational systems in the world. GOFS16 is based on the NEMO ocean/sea ice modelling framework coupled to a three-dimensional variational data assimilation method to provide daily initialization fields. The system assimilates salinity and temperature profiles, sea surface temperature, along track sea surface height, and sea-ice concentration on a daily basis. The forecast system is forced with 3-hourly momentum, radiation, precipitation fluxes from the operational Global Forecast System (GFS) fields, and it runs operationally once a day to produce a 7-day forecast of the three-dimensional temperature, salinity, velocity fields, and sea-ice properties. An overview of the system is presented together with an extensive assessment of its predictive skills.

This forecast system is also used for several downstream applications, namely regional and coastal downscaling in several regions of the world ocean. Downscaling is realized with a new tool, the Structured and Unstructured Relocatable ocean model for Forecasting (SURF) based on NEMO, reaching resolutions of 1/64° and nested within the global operational model. SURF produces forecasts every day with best initial and boundary conditions from GOFS16. An overview of the system is presented.