The simulation of a radar altimeter return waveform

We analyze the capabilities and limitations of the Gram-Charlier distribution of rough sea-surface elevations in describing the return waveform during vertical sounding. We show that for typical values of skewness and kurtosis of the distribution of sea-surface elevations, the calculated return waveforms obtained with the Gram-Charlier distribution are distorted (including the occurrence of negative values). A new approach based on a combined model of the distribution of sea-surface elevations is proposed that is free of the disadvantages associated with the Gram-Charlier distribution.