Effect of temporally varying parameters on L- and C-band SAR observations of boreal forests

An analysis of L- and C-band boreal forest backscattering properties with respect to various temporally changing parameters is presented. The seasonal or weather dependent parameters investigated include the depth of soil frost, top-soil moisture, snow water equivalent, air temperature and precipitation. The effect of these parameters on σ° are studied for various stem volume (biomass) classes by comparing the results against a semi-empirical modelling approach. Semi-empirical modelling is also used for a forest biomass retrieval experiment. The SAR data set includes 4 JERS-1 (L-band, HH-polarization) and 19 ERS-1 (C-band, VV-polarization) images for a single test area in southern Finland. The results show that at C-band response to forest biomass is more sensitive to changes in temporally varying parameters than at L-band. The semi-empirical modelling approach was found to describe well the behavior of σ° when large areas are considered. Hence, the results in biomass retrieval show high accuracies (25-30% relative accuracy) when areas under investigation are larger than 20 ha