Empirical microwave backscattering over Antarctica: application to radar altimetry

Abstract

In order to validate the satellite altimeter measurements over Antarctica, we analyze the Seasat scatterometer backscatter coefficient which has been measured at different incidence and azimuth angles and for the two polarizations. We show that the signal at large incidence angles is a mixed signal of volume, backscattered by subsurface layering and surface scattering whose proportions depend on physical characteristics of the snow. Only the effect of the volume scattering by spherical grains on the altimetric signal can be estimated: It is of the order of a few percents of the total altimetric signal and the induced height error is lower than 25 ± 20 cm, if the echo is properly retracked. Other effects, such as internal density boundary are not estimated but a mean to detect the areas of great effect is given.