Comparative Analysis of SWH Retrieval Between BDS-R and GPS-R Utilizing FY-3E/GNOS-II Data

High-precision sea surface significant wave height (SWH) data are crucial for advancing oceanic shipping and marine resource development. In this study, we conducted a comparative analysis of parameter sensitivity and accuracy in SWH retrieval between BDS-R and GPS-R based on multi-global navigation satellite system reflectometry (GNSS-R) system data from the Fengyun-3E satellite. Initially, a sensitivity analysis of delay–Doppler map observations, including leading edge slope (LES), normalized bistatic radar cross section, and normalized signal-to-noise ratio, was performed against the ERA5 SWH using the multiple linear regression approach. The results highlighted LES as the most sensitive parameter influencing SWH, with BDS-R LES demonstrating superior performance compared with GPS-R LES, achieving a lower root-mean-square error, potentially due to its broader bandwidth. Subsequently, based on LES observations and the double exponential function, we developed a GNSS-R SWH retrieval model and validated its accuracy using ERA5 SWH data and ocean buoy data. Results demonstrate that BDS-R slightly outperforms GPS-R in SWH retrieval, with an accuracy of up to 0.52 m (0.55 m for GPS-R), and both exhibit high correlations of 0.90 in the retrieved results. Moreover, an evaluation using NDBC buoy data indicates that BDS-R surpasses GPS-R in terms of accuracy, correlation, and bias, aligning with the results from the sensitivity analysis. This study provides theoretical and technical guidance for achieving higher precision SWH retrieval in the future using broader bandwidth global navigation satellite system signals.