Retrieve the Surface Wave Information from X-Band Radar Images

The sea clutter image from X-band radar contains many information of the sea surface. Applying three-dimensional Fourier transform to the time series of sea clutter images can obtain a three-dimensional (3-D) image spectrum of sea clutter. The radar return causes Doppler frequency-shift, because of the relative movement between the radar antenna and the sea surface. The surface current is obtained by minimizing the distance between the localization of the spectral energy in the image spectra of sea clutter and its theoretical position given by the dispersion relation for linear surface gravity waves. Using the modulation transfer function (MTF) between the image spectra of sea clutter and the wave directional spectrum, a directional wave spectrum can be acquired. Comparing the frequency spectra and the mean directional spreading which are respectively obtained from radar and buoy within the ground-based and ship-based experiments, it is available to obtain the reliable wave information using X-band radar images.