In-situ validation of small-scale spatial variability in significant wave height observations from SWOT

Small-scale variations in wave heights arise from interactions with mesoscale and submesoscale ocean currents. The Surface Water and Ocean Topography (SWOT) mission offers unprecedented observations of this variability with two-dimensional interferometric measurements of significant wave height (SWH). In this study, we evaluate the accuracy of SWOT's wide-swath SWH estimates at an open-ocean calibration site off Central California by comparing them to high-precision in-situ wave measurements from a closely-spaced array of moorings designed to capture centimeter-scale variations in sea surface height. We validate SWOT SWH measurements to the mooring array (CC>0.99, RMSE < 0.015 m). Additional comparison to a network of coastal wave buoys is consistent with SWOT's performance at the mooring array. We find that SWOT accurately resolves gradients in wave conditions over short spatial scales (10-70 km), and better represents spatial variability in SWH than either traditional altimetry or operational numerical wave models run without currents. Overall, these findings validate SWOT’s wide-swath observations as a powerful tool for observing and understanding ocean surface wave conditions and their connection to ocean currents.