Model Validation with a Diagram Comparing Amplitudes and Phase Lags Between Observed and Simulated Tidal Constituents in Tokyo Bay

We access model performance for tides and tidal currents in Tokyo Bay using a diagram, which shows the amplitude and phase of observed and simulated tidal constituents and simultaneously complex distance related to the RMSD and the correlation of both the time series. The diagram highlights improvements in the representation of the phase and amplitude of diurnal tides by the model and shows that the observed semidiurnal tidal levels at all gauges in Tokyo Bay are satisfactorily represented, although the simulated tidal harmonic constants differ slightly from those observed at the gauges near the bay mouth, where the tidal boundary conditions are set. A diagram on which the harmonic constants normalized by the tidal harmonic constant at the innermost gauge, Chiba, are plotted shows that the model can reproduce a standing wave tide. The semi-major axes (MAs) of the simulated and observed M2 tidal current ellipses at Chiba were compared using a diagram on which the clockwise and counterclockwise current vectors (CV and CCV) and MA were plotted. The observed (and simulated) magnitudes of CV and CCV were nearly identical, indicating that both tidal current ellipses are simple linear oscillations. The observed MA (2.1 cm/s) was smaller than the simulated MA (3.1 cm/s) and rotated about 15° counterclockwise from that modeled, and the observed flood tide peak was 26° ahead of the simulated peak. Thus, the diagrams allow visual assessment of the model's performance for tides and tidal currents.