Evaluation of gridded sea surface height products based on along-track altimeter data

Sea surface height (SSH) is a critical parameter for characterizing ocean dynamics and understanding mesoscale eddies, surface currents, and subsurface thermohaline structures. Using along-track data from Haiyang-2B (HY-2B) as a reference, this study evaluated three SSH products for the year 2022 globally and in specific regions: the Copernicus Marine and Environment Monitoring Service (CMEMS) delayed-time (DT) merged gridded product, the CMEMS near-real-time (NRT) merged gridded product, and the Global Ocean Reanalysis and Simulation System (GLORYS) reanalysis product. The CMEMS DT product outperformed the others, achieving the lowest global root mean square error ( RMSE, 0.0267 m) and highest correlation, and demonstrated superior signal reconstruction, particularly in dynamically active regions such as the Kuroshio region. The NRT product offers reliable large-scale monitoring capability but shows higher errors in energetic regions, whereas GLORYS, despite its multivariate consistency, exhibits limited skill in resolving smaller-scale signals. For studies focusing on fine-scale and mesoscale features, the DT product is strongly recommended. For real-time large-scale applications, the NRT product is suitable with due regard to limitations in high-dynamic regions. Conversely, when employing GLORYS reanalysis in dynamically active areas, users should carefully evaluate its capacity to reproduce small- and mesoscale processes.