Identification of semidiurnal internal tides around the Korean Peninsula

Abstract

This research investigated the behavior of semidiurnal internal tides in the East/Japan Sea and used the plane wave fitting method to identify them. Based on hourly sampled sea surface height data from a numerical model (MITgcm) for two different months, the wavenumber and the size of the fitting window are estimated. The wavenumber for each fitting window is computed from the properties of the water column within the window. In contrast, the size of the fitting window is computed from the sea surface height spectrum in the wavenumber domain. Barotropic signal has been separated from the baroclinic signal by using a high-pass filter in the spatial domain, with a cut-off length that depends on the length of the sampling line. The number of tides and their direction needed to reconstruct the semidiurnal tide field have been identified. The plane wave fitting method identifies the first mode of the semidiurnal tides. The amplitude and propagation of internal tides are different in January and July. The variance in harmonic analysis and the plane wave fitting method is performed to determine if the plane fitting method identifies only the first mode of the semidiurnal tide. The variance in the plane wave fitting method is higher near the Korean strait, where they originate, and it decreases everywhere else. Thus, the method does identify both the temporal and spatial variability of the semidiurnal tide.