Deriving Coastal Sea Surface Current by Integrating a Tide Model and Hourly Ocean Color Satellite Data

Sea surface currents (SSC) play a pivotal role in material transport, energy exchange, and ecosystem dynamics in coastal marine environments. While traditional methods to obtain wide-range SSC, such as satellite altimetry, often struggle with limited performance in coastal regions due to waveform contamination, deriving SSC from sequential ocean color data using the Maximum Cross Correlation (MCC) has emerged as a promising approach. In this study, an enhanced MCC method called the Tide-Restricted Maximum Cross Correlation (TRMCC) is proposed and implemented on hourly ocean color data obtained from the Geostationary Ocean Color Imager II (GOCI-II) to derive SSC in coastal seas and turbid estuaries. Cross-comparison over three years with buoy data, high-frequency radar, and numerical model products shows that the TRMCC is capable of obtaining high-resolution SSC with good accuracy in coastal and estuarine areas. Both large-scale ocean circulation patterns in seas and fine-scale surface current structures in estuaries can be effectively captured. The deriving accuracy, especially in coastal and estuarine areas, can be significantly improved by integrating tidal current data into the MCC workflow, and the influence of invalid data can be minimized by using a flexible reference window size and the Normalized Cross-Correlation in the Fourier Domain technique. Seasonal SSC structure in Bohai Sea and diurnal SSC variation in the Yangtze River Estuary were depicted via satellite method for the first time. Our study highlights the vast potential of the TRMCC to be able to improve understanding of current dynamics in complex coastal regions.