Analysis of scattering mechanisms in SAR imagery over boreal forest: results from BOREAS '93

As part of the intensive field campaign (IFC) for the Boreal forest ecosystematmosphere research (B OREAS) project in August 1993, the NASA/JPL AIRSAR covered an area of about 100 km x 100 km near the Prince Albert National Park in Saskatchewan, Canada. At the same time, ground-truth measurements were made in several stands which have been selected as the primary study sites. This paper focuses on an area including Jack Pine stands in the Nipawin area near the park. Upon examining the AIRSAR data from stands of old and young Jack Pine (OJP and YJP), distinct signatures are observed for each of the forest types at various frequencies and polarizations. We use a forest scattering model in conjunction with the ground-truth measurements to explain such behavior. The forest model includes the major scattering mechanisms by taking the forest component interactions into account. The contribution from each of the scattering mechanisms to the total backscatter is calculated and their differences for OJP and YJP stands are evaluated. The results are used to discuss the effect of the physical properties of the forest components in each stand on radar backscatter. They are also used to show that it is not only the backscatter level but also the relative contribution from various scattering mechanisms that will help imquamtitative interpretation of SAR data. This work is mainly intended as a precursor to our ongoing work which uses a mechanism-specific inversion technique to retrieve forest parameters from SAR data for these BOREAS sites.