Accuracy assessment and waveform analysis of CryoSat-2 SARIn mode data over Antarctica

The new synthetic aperture radar interferometric (SARIn) measurement mode of CryoSat-2 provides better performance on the rough topography of the ice sheet margins than that of conventional radar altimetry. We assess the accuracy of CryoSat-2 SARIn mode data from Baseline C product of the European Space Agency (ESA), through comparison with two airborne laser altimeters on NASA IceBridge missions. The time difference between two compared data was limited to 30 days resulting in a reduction in the random error of ~0.3 m. We also assess the sensitivity of ESA retracker to surface slope, roughness and firn density using the mean waveform and retracked bin derived from CryoSat-2 Level 1B and Level 2i product. The ESA retracker appears to be sensitive to the surface slope and roughness according to the different leading edge shape and the retracked bin locations, however, not sensitive to the different firn density over four ice shelves. The modelled echo waveforms as SARIn are also used to analyse the impacts of surface characteristics (slope, roughness, and penetration depth) on echo waveform shape. It illustrates that the processes for ESA product fail to differentiate the changes in near-surface dielectric properties and determine radar-signal-penetration depth.