ECMWF Reanalysis 5 (ERA5)

ERA5 is the fifth-generation atmospheric reanalysis from the European Centre for Medium-Range Weather Forecasts, produced by the Copernicus Climate Change Service and covering 1940 to the present. It assimilates decades of surface, radiosonde, aircraft, and satellite observations into the ECMWF Integrated Forecasting System using 4D-Var, on a roughly 31 km grid with 137 vertical levels and hourly output. ERA5 carries an uncertainty estimate from a 10-member ensemble at coarser resolution. Its 10 m winds, sea-level pressure, waves, and surface fluxes are the standard forcing for ocean and wave models and the reference for metocean climatology and weather-routing hindcasts.