Calibration of Parameters for Regional Ocean Model Systems Using the Tidal Currents by Ocean Radar in the Ise Bay, JAPAN

We estimated the parameters for the Regional Ocean Models Systems (ROMS) using the M2 tidal velocities by MILT (Ministry of Land, Infrastructure, Transport and Tourism, JAPAN) HF Radar installed at the coast in the Ise Bay, JAPAN. We first evaluated the accuracy ratio between tidal levels and Radar currents for the objective function to calculate the average and variance-covariance matrix from 13 M2 constituents of levels and velocities by a harmonic analysis of 13 sequential 151 days data, which were observed from 22nd Apr. 2008 to 8th Oct. 2013. Since the M2 tidal constituents show periodicity of 18.6-years, which is an f-value, in the amplitude related to the lunar nodal tidal cycle, the constituents were calibrated with the f-value before the calculation of the average and variance-covariance matrix. The variance-covariance of currents represented similar to the geometric dilution of precision represented by the angle of the radar beams (Chapman et al., 1997). We estimated the appropriate parameter and boundary condition for the model, of which resolutions are 1/360 º in horizontal and 45 layers in vertical, by Green's function approach (GFA) to minimize the objective function consisting of the model results and the average and variance-covariance matrix of observations. We estimated two control parameters; (1) the magnitude of tidal current ellipses and sea level for the lateral boundary condition and (2) the sea bottom drag coefficient. The calibrated magnitude suggested that we did not need to change the magnitude. The drag coefficient was estimated to be 20.0 × 10^-3. The estimated drag coefficient improved the phase lags between the velocities and sea levels for the model. The GFA provided the horizontal distribution of M2 tidal currents and levels with high resolution and the M2 volume transport through the bay mouth with the errors.