NUMERICAL EXPERIMENT WITH MODELED RETURN ECHO OF A SATELLITE ALTIMETER FROM A ROUGH OCEAN SURFACE AND A SIMPLE ITERATIVE ALGORITHM FOR THE ESTIMATION OF SIGNIFICANT WAVE HEIGHT

We have simulated the return echo of a satellite altimeter from a rough ocean surface using an analytical formula and have studied its sensitivity with respect to various oceanic and altimeter parameters. Our numerical experiment shows that for normally observed significant wave heights (SWH) the effect of off-nadir angle (ONA) up to 0.5-degrees on the leading edge is not severe. Also, small surface roughness skewness seems to have little effect on the overall shape of the echo. Newton's iterative scheme has been used to retrieve SWH from the mean return waveform without noise and with additive Gaussian noise typical of Seasat and Geosat altimeters. It has been observed that SWH can be retrieved in the presence of noise with an accuracy of +/- 0.6 m for ONA less than 0.5-degrees. For higher ONA, accurate retrieval requires the use of precomputed look-up table along with our scheme.