Retrieving total suspended matter concentration in Fujian coastal waters using OLCI data

摘要

Total suspended matter (TSM) is an important indicator to evaluate water quality, and is also one of the key parameters for ocean color remote sensing inversion. The Ocean and Land Color Instrument (OLCI) is a new generation of ocean water color sensor with well spectral and spatio-temporal resolution. This paper adopted CatBoost, Random Forest and multiple regression methods to establish the TSM concentration inversion model based on OLCI data and in-situ observations, and the validation dataset was used to evaluate the model accuracy. The results showed that the CatBoost model had the highest accuracy with RMSE of 2.76 mg·L~(-1), MAPE of 23.67%, and R~2 of 0.89. Finally, the CatBoost model was applied to the time-series OLCI images to obtain the distribution of TSM concentration in Fujian coastal waters. The results indicated that the spatial and temporal variation of TSM concentration was significant, and the general pattern presents that the near-shore is higher than the far-shore, north region is higher than south region, estuaries and harbors are higher than other region, spring is higher than summer. This study provides a new method for retrieving TSM concentration, and further proves the good water color inversion ability of OLCI images, which can provide an effective remote sensing data for water quality monitoring in the Fujian Province.