Diurnal Variability of Submesoscale Chlorophyll‐a Fronts Revealed by Hourly Geostationary Satellite Observations

Abstract The detection of submesoscale fronts is critical for understanding physical‐biological interactions and ecosystem variability. This study characterizes the diurnal variability of chlorophyll‐a (Chl‐a) fronts using hourly data from the geostationary satellite GK‐2B/GOCI‐II in the East/Japan Sea. Chl‐a fronts exhibited more diverse and coherent submesoscale structures than sea surface temperature‐based fronts. During the spring bloom, front area and number followed a dome‐shaped diurnal cycle, peaking near local noon. Fronts also shifted horizontally in alignment with surface currents under strong flow, while deviating under weak flow, suggesting biological influences. These findings reveal distinct diurnal dynamics in Chl‐a fronts not captured by physical parameters alone.