  Understanding the scattering mechanisms from the ground surface in the
presence of different vegetation densities is necessary for the interpretation
of P-band Synthetic Aperture Radar (SAR) observations and for the design of
geophysical retrieval algorithms. In this study, a quantitative analysis of
vegetation and soil scattering mechanisms estimated from the observations of an
airborne P-band SAR instrument across nine different biomes in North America is
presented. The goal is to apply a hybrid (model- and eigen- based) three
component decomposition approach to separate the contributions of surface,
double-bounce and vegetation volume scattering across a wide range of biome
conditions. The decomposition makes no prior assumptions about vegetation
structure. We characterize the dynamics of the decomposition across different
North American biomes and assess their characteristic range. Impacts of
vegetation cover seasonality and soil surface roughness on the contributions of
each scattering mechanism are also investigated. Observations used here are
part of the NASA Airborne Microwave Observatory of Subcanopy and Subsurface
(AirMOSS) mission and data have been collected between 2013 and 2015.
