A Coupled Vegetation–Soil Bidirectional Reflectance Model for a Semiarid Landscape

A model for the bidirectional reflectance over soils is coupled with a vegetation reflectance model to predict the bidirectional reflectance of semiarid landscape. The vegetation model is a hybrid of geometric optical and radiative transfer (GORT) model for bidirectional reflectance over discontinuous plant canopies. The coupling is done by relaxing the assumption of Lambertian background into a non-Lambertian case in the vegetation GORT model. The non-Lambertian soil background is modeled by a soil BRDF model. The coupled model is validated with POLDER and AVHRR imagery collected in a semiarid site during the Jornada PROVEʹ97 campaign with good accuracy. It is a very simple but analytical model for bidirectional reflectance over a semiarid landscape and has the potential for surface parameter retrieval for the study of biosphere–atmosphere interaction.