A description of validation processes and techniques for ocean forecasting

<strong class="journal-contentHeaderColor">Abstract.</strong> The architecture of operational forecasting systems requires clear identification of best practices for assessing the quality of ocean products: it plays a key role not only for the qualification of prediction skill but also for the advancing of the scientific understanding of the ocean dynamics from global to coastal scales. The authors discuss the role of the observing network in performing validation of ocean model outputs, identifying current gaps (i.e. different capacity to assess physical essential ocean variables versus biogeochemical ones) but also emphasizing the need for new metrics (tailored for end users' comprehension and usage). An analysis on the level of maturity of validation processes from global to regional systems is provided. A rich variety of approaches exist, and the more we move towards the coast, the higher the complexity in calculating such metrics is, due to increased resolution, but we are also somehow limited by the lack of coastal observatories worldwide. An example is provided of how the Copernicus Marine Service currently organizes product quality information from producers (with dedicated scientific documentation, properly planned and designed) to end users (with publication of targeted estimated accuracy numbers for its whole product catalogue).