Analysis of satellite radar-altimeter return wave forms over the East Antarctic ice Sheet

The precision of satellite-radar altimetry over the Antarctic ice sheet can be improved by using a physically based retracking algorithm on the altimeter returns ("wave forms"). Ridley and Partington (1988) have shown that both surface and volume-scattering affect the shape of the return. Here, we develop a model that is based on a variable combination of surface- and volume-scattering and determine the model parameters through least-square fitting to the observed wave forms. The model parameters include surface roughness, proportion of volume-scattering, extinction coefficient and an amplitude coefficient. Geosat data collected over a test sector of the East Antarctic ice sheet have been analyzed to find quantitative estimates of seasonal and geographic variations of the several parameters. Our results show that the effect of volume-scattering can change the elevation measurement over the inland part of the East Antarctic ice sheet by more than I m and that there are both spatial and temporal variations; temporal variations are less significant than spatial variations.