A Comparative Assessment of Multi-Model Dissolved Organic Matter Absorption Algorithms Using GOCI-II in Korean Coastal Waters

Accurate retrieval of dissolved organic matter absorption at 440 nm (aDOM(440)) remains challenging in optically complex coastal waters. This study evaluated eight empirical algorithms using 203 paired observations of in situ aDOM(440) and remote-sensing reflectance from four marine regions surrounding Korea. Five formulations were recalibrated using Huber regression with a log10-transformed response, while three established algorithms retained published coefficients. The dataset comprised 162 calibration and 41 held-out validation observations. HYB1 achieved the highest calibration R2 (0.416), whereas HYB2 performed best in validation (R2 = 0.500; RMSE = 0.0198 m−1), followed by MR4B (R2 = 0.486; RMSE = 0.0200 m−1). Bootstrap resampling of fixed validation predictions indicated comparatively lower variability in R2 for HYB2 and MR4B, with overlapping confidence intervals. Leave-one-region-out cross-validation highlighted limited geographic transferability, particularly for HYB2 and MR4B in the West Sea. Applying the algorithm to Geostationary Ocean Color Imager-II (GOCI-II) imagery revealed algorithm-dependent retrieval magnitudes and spatial patterns; accuracy assessment requires concurrent field observations. These findings identify HYB2 and MR4B as promising candidates for regional refinement and provide a foundation for advancing GOCI-II-based monitoring of coastal aDOM(440).