Exploring The Effective Resolution Of Copernicus Marine Service Eddy Resolving Systems With Spectral Analysis: A Metric To Evaluate High Resolution Forecasts

In the framework of the Copernicus Marine Environment Monitoring Service (CMEMS), Mercator Ocean delivers in real-time daily services with a global 1/12° high resolution system. The quality of the analyses and forecasts is checked with a series of metrics inherited from the European projects MERSEA and MyOcean, and the international initiative GODAE Oceanview. High resolution forecasts display more realistic ocean circulation and energy levels than coarser forecasts. However, the small scales are not yet systematically constrained by data assimilation for various reasons: availability of high resolution observations, background and observation error tunings, representativity of models and observation operators issues, etc… This can result in forecasts displaying realistic small scale features, but slightly shifted in space and time with respect to observations, which is not taken into account by simple “observation minus forecast” metrics. Consequently, specific metrics have to be developed for high resolution forecasting systems, and furthermore for coastal forecasting systems. For this presentation we will study along track Sea Level Anomaly spectra and explore their capacity to quantify the added value of high resolution forecast with respect to coarser resolution forecasts. The spectra of various CMEMS analysis and forecast products will be compared with the observations spectrum. This analysis will be done in several regions which experience different spatio-temporal variability regimes.