An integrated evaluation for SWOT KaRIn Level-2 significant wave height product

Significant wave height (SWH) is a crucial parameter for studying ocean wave fields. Conventional nadir altimeters provide global SWH records via along-track sampling, yet their limited effective resolution constrains the capture of small-scale wave variability. The Surface Water and Ocean Topography (SWOT) mission’s Ka-band Radar Interferometer (KaRIn) enables wide-swath, high-resolution SWH observations. However, most existing validations focus on pointwise accuracy and do not quantify cross-swath variability or link absolute accuracy to scale-dependent performance. This study develops an integrated evaluation framework with two components: (i) a collocation-based accuracy assessment of KaRIn SWH against National Data Buoy Center buoys and altimeters (Jason-3, HY-2B, and SWOT-nadir); and (ii) a scale-aware analysis based on power spectral densities to derive spectral slope, band-limited signal-to-noise ratio (SNR), and the effective resolution (λp), explicitly characterizing cross-track performance variations. KaRIn SWH has a bias of 0.11 m and RMSE of 0.43 m relative to buoys, indicating lower pointwise accuracy than nadir measurements. Cross-track analysis provides quantitative guidance for use. Near nadir, KaRIn SWH bias is typically