BACKSCATTERING PROPERTIES OF BOREAL FORESTS AT THE C-BANDS AND X-BANDS

The backscattering properties of boreal forests are studied using empi rical airborne and spaceborne radar data from Finland. Airborne measur ements were carried out in the summer of 1992 by the HUTSCAT scatterom eter at the Teijo test area in southern Finland. The HUTSCAT scatterom eter is an eight-channel helicopter-borne profiling radar operating at the C- and X-bands. The ranging capability of the HUTSCAT scatteromet er was employed in the semiempirical modeling of forest backscatter. T he backscatter profile information was used in the analysis of the can opy transmissivity and the canopy backscattering coefficient by distin guishing backscattering contributions from the canopy and the ground. Additionally, ERS-1 C-band satellite SAR measurements were obtained fo r the Teijo test area and for the reference test area in Sodankyla in northern Finland. The radar results were compared with operational gro und-based forest,assessment data on forest compartments (stands) of th e area. The key parameter investigated was the stem (bole) volume per hectare. The results obtained show the behavior of the canopy transmis sivity and the canopy backscatter as a function of stem volume (direct ly related to the forest biomass). The influence of seasonal and diurn al changes on, and the effects of the changes in soil moisture to the backscattering coefficient were also investigated.