The Marine Environment Reanalyses Evaluation Project MER-EP: towards an improved knowledge of the global ocean environment of the past decades, to support ocean applications and ocean prediction.

Ocean reanalyses are reconstructed past ocean states by combining ocean numerical models and observations through data assimilation techniques. Thanks to their temporal and spatial consistency, continuity, and high accuracy, ocean reanalyses are an important tool for a wide range of applications

The MER-EP project we present, endorsed by UN Ocean decade action, is an international effort build on previous ocean reanalysis intercomparison exercises such as the Ocean Reanalyses Intercomparison Project (ORA-IP), and on the joint efforts of the ocean prediction community (Copernicus Marine Service, Oceanpredict/ForeSea/OP-DCC), the ocean and climate modelling research community (CLIVAR/GSOP), and on the Ocean Physics and Climate panel of the Global Ocean Observing System (GOOS/OOPC) research program.

Previous intercomparison exercises of ocean reanalyses have targeted specific variables to assess the consistency and discrepancies among various ocean reanalysis products. MER-EP will complement this approach including more systematic to evaluate different ocean reanalyses to determine their quality and fitness-for-purpose for specific applications.

Therefore, the main objective of MER-EP is to improve our knowledge of the ocean by understanding and ultimately improving the reliability and usability of global and regional ocean reanalyses, including physics, waves, biogeochemistry, and sea ice. This work is based on representative and high-priority use cases identified after extensive discussions with academic and private sectors ocean reanalyses users. In the proposed presentation, the MER-EP general organization, the development plans and first results will be given.