Quality Control of Surface Wave Data Estimated from Low Signal-to-Noise Ratio HF Radar Doppler Spectra

Ocean wave spectra estimated by high-frequency (HF) radar are very sensitive to the noise of Doppler spectra. The method for estimating wave spectra has been improved. This method is a nonlinear inversion and can be applied to a single radar case by combining the energy balance equation and the regularization constraint. A simple method for selecting radar-estimated wave data for various weights of the nonlinear weighted least squares problem and initial guesses of the iterative algorithm is proposed. This method is based on the residuals of the objective function to be minimized and is then applied to observed Doppler spectra. The selected radar-estimated wave heights using the method correlated well with in situ observations, even in conditions of low signal-to-noise ratios of Doppler spectra, low wave heights, and small temporal variations of wave heights. The optimal value of the criterion of the residuals is dependent on the required wave height accuracy and number of selected radar-estimated wave data.