In Situ Validation of Small‐Scale Spatial Variability in Significant Wave Height Observations From SWOT

Abstract Ocean surface wave climates are shaped by both atmospheric forcing and underlying ocean conditions. Variability in open‐ocean wave heights subsequently reflects complex interactions occurring across a broad range of spatial and temporal scales. Many of the processes driving this variability take place at small spatial scales that have been previously poorly resolved by sparse altimetry observations and coarse global wave models. The Surface Water and Ocean Topography (SWOT) mission offers a new opportunity to observe variability at these scales with unprecedented two‐dimensional measurements of significant wave height (SWH) from the Ka‐band radar interferometer (KaRIn). In this study, we evaluate the accuracy of SWOT's KaRIn SWH estimates at an open‐ocean calibration site off Central California by comparing them to in situ wave measurements from a closely spaced array of buoys. SWOT KaRIn SWH measurements are validated at the calibration site with high fidelity and perform consistently in additional comparison to a network of coastal wave buoys. The centered root‐mean‐square error ranges from 0.10 to 0.17 m across the various data sets and product versions, with correlation coefficients exceeding 0.98. Additionally we show that SWOT is capable of accurately resolving gradients in wave conditions over short spatial scales (10–90 km), and the high resolution two‐dimensional KaRIn observations better represents spatial variability in SWH than either traditional altimetry or coarse‐grid 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 broader ocean‐atmosphere dynamics.