Active and passive microwave signatures of Antarctic firn by means of field measurements and satellite data

The angular dependence and polarization behaviour of back-scattering and emission of polar firn at 5.2 GHz and 10.3 GHz were measured during an oversnow traverse in Dronning Maud Land, Antarctica. The signatures emphasize the importance of snow stratification in the interpretation of microwave remote sensing measurements. Highest backscattering coefficients and little angular variations were observed for refrozen firn near the coast. In permanently dry snow, areas with high accumulation rates and homogeneous snow morphology showed low backscattering coefficients and high emissivities. Pronounced layering and related density variations in low accumulation zones resulted in increased polarization differences of brightness temperatures and increased like-polarized backscattering coefficients. This behaviour is confirmed by the analysis of C-band scatterometer measurements of the Active Microwave Instrument aboard the European Space Agency's ERS-1.