Radiative Transfer Modeling of Cross-PolarizedBackscatter From a Pine Forest Using the DiscreteOrdinate and Eigenvalue Method
Résumé
Radiative transfer models have been widely usedto interpret the radar backscatter from forested areas. Most of these models are based on an iterative solution of the radiativetransfer equation, usually solved up to first or second order, thustaking into account single and double scattering. Although thismethod leadsto results agreeing well with copolarized backscattermeasurements, it produces less accurate estimates for hori-zontal–vertical (HV) polarization. This paper presents a radiativetransfer backscatter model that accounts for multiple scatteringby using the discrete ordinate and eigenvalue method applied to alayered medium. Using parameters derived from an architecturaltree model, calculations at C- and L-band are compared withHV data acquired for a maritime pine forest in the southwest of France during the Spaceborne Imaging Radar-C missions. Goodagreement is found at C-band for all values of forest biomass,and reasonable agreement at L-band for high biomass, when thesoil backscatter plays a minor role. For low biomass, the L-bandmodeling is inadequatebecauseof difficultiesin estimatingthe soilbackscatter. Comparison with calculations from a first-order ra-diativetransfermodelshowsthatmultiplescatteringissignificant,especially at C-band.