SWOT and Swath Altimetry: A Breakthrough for Global Ocean Prediction

Abstract Since its launch in December 2022, the SWOT (Surface Water and Ocean Topography) satellite with its KaRIn (Ka‐band interferometer) instrument has provided unprecedented, high‐resolution, two‐dimensional views of global Sea Surface Height (SSH), offering crucial insights into ocean dynamics. A first assessment of the impact of SWOT science phase data for global ocean analysis and prediction is carried out with the global 1/12° Mercator Ocean International (MOi) data assimilation system. Comparing experiments with and without SWOT assimilation (both assimilating three Sentinel nadir altimeters), we show that SWOT reduces SSH error variance by 18% in analyses and 15% in forecasts when evaluated against independent (i.e., not assimilated) altimeter data. This demonstrates the potential of SWOT data for global ocean prediction and paves the way for the use of SWOT data in operational systems such as those of the European Union Copernicus Marine Service.