Satellite Observations of South China Sea Warm Current and Its Synoptic Variability During Northeasterly Wind Relaxation

The South China Sea Warm Current (SCSWC) represents a significant circulation pattern in the Northern South China Sea (NSCS), yet its existence and characteristics remain controversial due to limited direct measurements. This study employs observations from the Himawari-8 satellite to map surface currents over the NSCS shelf. Rare continuous 4-day satellite observations offer a comprehensive view of the spatial pattern and synoptic variability of SCSWC, aligning well with concurrent satellite-observed sea surface temperature (SST) and salinity. Our findings indicate that the episodic SCSWC bursts appear highly sensitive to the rapidly weakening of northeasterly winds, evidenced by the corresponding surface winds. The composite analysis of five northeastward flow events further elucidates the relationship between wind forcing and surface currents. The comparison of the observed surface flows with the model currents confirms the transient response of the SCSWC to northeasterly wind relaxations. The self-organizing map (SOM) analysis identifies synoptic variability in northeastward flow events (~33.33%), occurring during weak northeasterly winds. This multidisciplinary approach enhances our insights into the SCSWC dynamics and holds promise for advancing oceanographic modeling and forecasting efforts in the region.