*4.1. Influence of Barotropic Tide*

The barotropic tide velocity can reach in the order of 10 cm/s in the northern SCS [22], which may contribute to the horizontal velocity in ADCP measurements. When considering the influence of the barotropic tide on the observed ISW, the barotropic tide should be calculated first. With long-term and all-depth observation records, the internal wave signal could be separated via filter analysis from tidal and inertial signals [2,23,24] to investigate the influence of the barotropic tide on the observed ISW. However, the vessel cannot provide full-depth current data due to ADCP measurement limitations. Instead, here we considered two other methods to subtract the velocity of the barotropic tide.
