Polarimetric Analysis of Biseasonal Monostatic and Bistatic Radar Observations of a Glacier Accumulation Zone at Ku-Band

Abstract

We present ground-based Ku-band radar observations of the snow cover on top of the Great Aletsch Glacier carried out over two observation periods, in August 2021 and in March 2022. The observations were carried out with the combined mono/bistatic version of KAPRI, a full-polarimetric radar system, and revealed substantial differences between the scattering behaviour of the snow cover between the two seasons. We analyze the spatial and temporal behaviour of parameters including temporal decorrelation, the scattering entropy, the mean polarimetric alpha angle, and the co- and cross-polarized phase differences. The results indicate that snow cover decorrelates at Ku-band on the timescales of 4-12 hours in winter and summer, which has implications for repeat-pass methods with long temporal baselines. The analysis of the co-polarized phase difference in winter indicates that the parameter is prone to phase wrapping. In summer, its value exhibits smooth spatial trend and a strong sensitivity to changes in incidence angle and liquid water content. The bistatic cross-polarized phase difference also acquires a non-zero value, indicating the presence of non-reciprocal scattering, which has implications for possible calibration procedures of bistatic systems. The presented results aim to serve as a reference for snow scattering behaviour at Ku-band, which can aid planning of future data acquisition campaigns and satellite missions.