A new method of retrieving surface bidirectional reflectance from ground measurements: Atmospheric sensitivity study

Commonly, experimental data on surface directional reflectance are not prop erly corrected for atmospheric effects. In this paper, we describe a new me thod for rigorous retrieval of the bidirectional reflectance distribution f unction (BRDF) from ground-based measurements. It obtains the pointwise BRD F in the view directions and the best fit parameters of the approximating a nalytical model. Unlike previously developed algorithms, it can perform a r etrieval using directional observations made at a single solar angle. This improvement allows one to process experiments with incomplete sets of measu rements, such as those contaminated by clouds. The paper describes the perf ormance of the method and its sensitivity to atmospheric parameters. Using rigorous direct modeling of the reflected radiance and developed inversion algorithm, we performed an analysis of BRDF errors, typical for measurement s. It shows that the BRDF shape distortions due to diffuse irradiance are c onsiderable in the visible and near-IR, even for low aerosol content in the atmosphere. This result confirms that an accurate atmospheric correction s hould be a required processing step in the experimental research of anisotr opic surface reflectance.