Characterizing Tidal Currents and Guangdong Coastal Current Over the Northern South China Sea Shelf Using Himawari-8 Geostationary Satellite Observations

Obtaining high spatiotemporal resolution surface currents with wide coverage is of great importance for understanding marine physical and biogeochemical processes, as well as practical applications. This study utilizes the sequential hourly images from the Himawari-8 geostationary satellite to map the semidiurnal M2 surface tidal current pattern over the shallow shelf (<100 m) of the northern South China Sea. The comparison between the satellite-derived tidal currents and the High-Frequency Radar observations shows good agreement. The satellite-derived tidal currents are also fairly comparable to the prediction of the regional tidal model from Oregon State University. The detided daily mean surface flows provide an apparent representation of the spatial pattern of the Guangdong Coastal Current (GCC) and its synoptic variability, well consistent with the simultaneous sea surface temperature and salinity satellite observations. The observed surface flows are compared to the Copernicus Marine Environment Monitoring Service daily model currents, and the model findings are in good agreement with the observations, indicating the sensitivity of the GCC to rapid changes of northeasterly winds. This study highlights the potential of the Himawari-8 geostationary satellite in measuring sea surface currents over a broad, shallow continental shelf.