Polarization signatures of frozen and thawed forests of varying biomass
During two different overflights (by the JPL radar polarimeter) of the Bonanza Creek Experimental Forest, the environmental conditions changed significantly with temperatures ranging from unseasonably warm (1 to 9°C) to well below freezing (-8 to -15°C), and the moisture content of the snow and trees changed from a liquid to a frozen state. Preliminary investigations have focused on the characterization of the radiometric and polarimetric signatures of the data. Significant changes (up to 6 dB in certain forest stands) were observed in the L-band radar cross sections. Features extracted from the Stokes matrices of the same stands from the thawed and frozen days also suggest the relative contribution of the different scattering mechanisms to the radar return. Comparison of the diffuse component and variance of the H-V phase (white spruce, for example) indicates a relatively higher contribution from diffuse scatterers on the thawed day than on the frozen day. These results indicate that the contribution of scattering from the crown is responsible for this appreciable increase in backscatter. Some of these preliminary L-band and P-band observations are presented.