The First 1/12° Global Ocean Reanalysis of Copernicus Marine Environment Monitoring Service: Description and Quality Assessment

Romain Bourdalle-Badie1, Jean-Michel Lellouche2, Mathieu Hamon3, Marie Drevillon2, Eric Greiner4, Gilles Garric2, Olivier Le Galloudec2, Clement Bricaud2, Charly Regnier2, Tony Candela5 and Yann Drillet6, (1)Mercator-Ocean, Ramonville, France, (2)Mercator Océan, Ramonville Saint Agne, France, (3)Mercator-Ocean, France, (4)CLS, Ramonville Saint Agne, France, (5)Mercator Ocean, Operational Oceanography, Ramonville St Agne, France, (6)Mercator Ocean international, Toulouse, France
Abstract:
Over the past years, Mercator Ocean has been regularly upgrading its global ocean physical reanalysis through improvements in the ocean model, assimilation scheme and assimilated data sets. R&D activities have been conducted at Mercator Ocean International (MOI) to propose, in the framework of Copernicus Marine Environment Monitoring Service (CMEMS), a global eddy-resolving physical reanalysis (called GLORYS12V1), covering the altimetry era (1993-present) and based on the current real-time global forecasting CMEMS system of the year 2016.

The model component is the NEMO platform driven at the surface by ECMWF ERA-Interim reanalysis. Observations are assimilated by means of a reduced-order Kalman filter. Along track altimeter data (Sea Level Anomaly – SLA), satellite Sea Surface Temperature (SST), Sea Ice Concentration and in situ temperature and salinity (T/S) vertical profiles are jointly assimilated. Moreover, a 3D-VAR scheme provides a correction for the slowly-evolving large-scale biases in temperature and salinity.

Compared to previous MOI reanalysis, except the horizontal resolution, GLORYS12V1 reanalysis benefits from manly updates: global steric effect added to the model sea level, new seasonal observation error for assimilation of in situ T/S vertical profiles, adaptive tuning of observational SLA and SST errors, additional Quality Control on the assimilated T/S vertical profiles based on dynamical height criteria, assimilation in the deep ocean (below 2000m) of climatological T/S vertical profiles using a non-Gaussian error at depth.

This presentation will provide, first, an overall assessment of this first global 1/12° ocean reanalysis highlighting the level of performance and the reliability of this new eddy-resolving physical reanalysis. Then, a particular focus will be made on the meso-scale activity and the energy levels present in this new simulation. By comparison to observed data and to a twin reanalysis at a ¼° resolution, the impact of increasing the resolution is discussed.

Back to: Advances in Ocean Data Assimilation, Forecasting, and Reanalysis I