Mathieu Hamon (Mercator Ocean, France); Yann Drillet (Mercator Ocean, France)

The quality of Mercator Ocean analysis and forecasts highly rely on the availability and quality of the assimilated observations. A precise specification of the model and observation errors are required to get a dynamically consistent ocean estimate with all the different data sets assimilated within the data assimilation procedure.
As the ocean model configuration becomes more realistic and can resolve a broader range of scales and ocean processes, the altimetry data also benefit from improved corrections allowing detecting smaller scales with an increased precision. Here we revisit the impact of the altimetry constellation on the analysis and forecasts with the new global Mercator Ocean systems and show that an increasing number of altimeters allow a significant reduction of the analysis and forecast errors. Large regional discrepancies are found. Even the forth satellite altimeter brings information in most of the ocean regions in both the ¼° and 1/12° global systems.
The “observation” error is now estimated within the assimilation process. This error estimates include the instrumental error and the so called model representativity error, ie the error coming from the inability of the dynamical model to represent phenomena that are detected by the observations. We will check the robustness of the error estimates and its characteristic for the different altimeters within the different Observing System Evaluation experiments.