A study of sea surface height retrieval using Doppler measurements from numerically simulated low grazing angle backscatter data

A numerical study of the retrieval of sea surface height profiles from low grazing angle Doppler radar measurements is described. Backscattered fields computed using the method-of-moments for one-dimensional ocean-like surface profiles are used to examine properties of Doppler spectra versus range. "Discrete" behaviors observed in the Doppler spectra versus range are found to be related to similar behaviors in orbital velocity statistics obtained directly from the corresponding surface profiles. Differences between Doppler spectra are also observed between VV- and HH-polarizations, with VV-polarization showing smaller Doppler spectral widths in some situations. In order to improve understanding of the accuracies to be expected in surface profile retrievals from Doppler information, estimation errors for the Doppler centroid versus range are studied using a simplified signal model. Comparisons of the results of this signal model with the method-of-moments simulations show that shadowing and multi-path propagation effects cause errors in Doppler centroid estimation beyond those caused by speckle effects alone.