Satellite radar altimetric waveform simulation and retracking over coastal sea based on singular spectrum analysis

Satellite radar altimetric waveforms conform to Brown model over open oceans but are unconformable in coastal regions because of non-Gaussian distribution of the reflecting surface and the effects of topography and geophysics. The radar return is irregular and contains more noises. The ocean waveforms were simulated based on the Brown-Hayne model and the coastal waveforms were simulated by adding different noise into Brown-Hayne model. The appropriate ratio of coastal waveforms and ocean waveforms was chosen to construct the waveform series over tracks from sea to land and from land to sea, respectively. The singular spectrum analysis (SSA) was used to extract principal components of the waveform series and reconstruct new series by linearly combining the selected components. Then several waveform retracking algorithms were used to retrack the original series and reconstructed series respectively. According to the comparison of retracking gates of the two-waveform series, the SSA played an important role in waveform denoising and waveform restoration. The results showed that the combination of SSA and retracking methods could effectively estimate the mid-point of leading edge, which could improve the altimetry data quality over coastal seas.