AIFS Forecasts in Support of "Representing the Surface Ocean in ECMWF's Data-driven Forecasting System AIFS"

This dataset contains medium-range forecasts produced with four experimental configurations of the European Centre for Medium-Range Weather Forecasts’ Artificial Intelligence Forecasting System (AIFS): * AIFS Atmosphere (expver=izzy): atmosphere-only configuration;* AIFS Waves (expver=j34q): configuration including atmospheric and ocean-wave variables;* AIFS Ocean (expver=j072): configuration including atmospheric and surface-ocean variables;* AIFS Marine (expver=j0oh): jointly trained atmosphere–wave–ocean configuration. The dataset supports the analyses presented in: Hahner, S., Zampieri, L., Bidlot, J.-R., et al. (2026), “Representing the Surface Ocean in ECMWF’s data-driven forecasting system AIFS,” arXiv:2604.25559. The forecasts were initialised at 00 UTC every two days from 15 June 2023 through 15 December 2023. Each forecast extends to ten days. Although the models run with a six-hour timestep, the archived forecast output is provided every 24 hours, at lead times from 24 to 240 hours. The archived fields include: * air temperature at 850 hPa;* geopotential at 500 hPa;* 2-metre temperature;* 10-metre zonal and meridional wind components;* significant wave height;* selected two-dimensional surface-ocean fields. Variable availability depends on the model configuration. Consequently, not every variable is provided for every model. Atmospheric variables are available for all four configurations, while wave and ocean variables are included only for configurations that represent those components: * AIFS Atmosphere provides atmospheric fields, including near-surface meteorological fields;* AIFS Waves provides atmospheric and wave fields;* AIFS Ocean provides atmospheric and surface-ocean fields;* AIFS Marine provides atmospheric, wave, and surface-ocean fields. All fields, including the ocean variables, are provided on the ECMWF N320 grid. N320 is the native grid used by these experimental model configurations and was not selected as a separate post-processing or regridding choice for this dataset. The data were retrieved from ECMWF’s Meteorological Archival and Retrieval System (MARS), and all files in this archive are distributed in GRIB format. The four configurations provide a controlled comparison of progressively richer representations of the coupled Earth system. The dataset may be used to reproduce figures and evaluation results from the associated publication, compare atmosphere-only and marine-aware AIFS forecasts, and investigate interactions across the atmosphere–ocean interface. Important disclaimer These data were generated using experimental research configurations of AIFS. They must not be interpreted as an announcement, preview, or specification of any current or future operational version of AIFS at ECMWF. The configurations, model identifiers, variables, resolutions, and forecast behaviour represented in this archive are specific to the research experiments described in the associated paper and may differ substantially from operational forecasting systems. The forecasts are provided for academic and scientific research purposes only. They are not operational forecasts and must not be used for weather warnings, marine safety, emergency management, navigation, commercial decision-making, or any other activity requiring operational or time-critical forecast information. No warranty is provided regarding their accuracy, completeness, fitness for purpose, or continued availability.