Variations of Remote-Sensed Forel-Ule Index in the Bohai and Yellow Seas during 1997–2019

Water color, often quantified using the Forel-Ule Index (FUI), is a crucial parameter for assessing water quality and ecological health of coastal waters. However, there limited research on spatiotemporal variations FUI associated influencing factors in Bohai Yellow Seas. In this study, we utilized multi-sensor satellite datasets to retrieve monthly products Seas spanning period from September 1997 December 2019. Subsequently, examined significant spatial disparities across multiple timescales remotely sensed time series. The climatological annual mean map reveals decreasing trend nearshore offshore regions, with similar patterns observed terms overall interannual variability. wind field, sea surface temperature (SST), ocean stratification play key role seasonal dynamics by modulating sediment resuspension process, resulting low values summer high winter. Linear regression analysis anomaly indicates long-term three bays Sea, while upward trends predominantly prevail central Sea. Factors related variations, such as winds, SST, river outflow, rainfall, anthropogenic activities, are qualitatively discussed. findings study provide first comprehensive evaluation color their underlying mechanisms