Improved Significant Wave Height Retrieval from SAR Imagery in Tropical Cyclones Using Wind-Context Proxies

Accurate retrieval of significant wave height (SWH) under tropical cyclone (TC) conditions is essential for marine hazard warning and ocean dynamics studies. Although spaceborne synthetic aperture radar (SAR) offers unique capabilities for observing extreme sea states, existing empirical wave retrieval models often do not fully account for TC wind context. This study presents CWAVE_S1TC, a wind-context-based extension of the CWAVE model, which incorporates three key proxies of TC wind context derived from SAR wind retrievals: the local surface wind speed, the maximum wind speed, and the normalized radial distance, to enhance SWH retrieval. A dataset comprising 63 Sentinel-1 SAR scenes from 40 TC events, together with collocated reference SWH from the ECMWF ERA5 reanalysis and WAVEWATCH III hindcast data, is used for model development and validation. The three proxies show significant correlations with SWH, with correlation coefficients of 0.84, 0.56, and −0.49, respectively. CWAVE_S1TC achieves a coefficient of determination of 0.81 and a root mean square error (RMSE) of 1.03 m, outperforming the basic CWAVE_S1 model in the model-development dataset. Independent validation against WW3 data shows that CWAVE_S1TC reduces the Bias from 0.61 m to 0.37 m and the RMSE from 1.86 m to 1.14 m, while increasing the correlation coefficient from 0.77 to 0.85. Leave-one-storm-out and cross-basin validation further demonstrate model robustness and applicability beyond the model-development region. These results highlight the value of incorporating TC wind-context information into SAR-based SWH retrieval and demonstrate the potential of CWAVE_S1TC for improving SWH retrieval under TC conditions.