UMass Boston

The BRDF, albedo and nadir surface reflectance of each pixel of the global land surface is modeled at a spatial resolution of 500m by inverting multi-date, multi-angular, cloud-free, atmospherically corrected, surface reflectance observations acquired by MODIS instruments on board the Terra and Aqua satellites over a 16-day period (MODIS orbital double repeat cycle).  The daily product weights the data as a function of quality, observation coverage and temporal distance from the day of interest. 

The product is derived using a kernel-driven semi empirical BRDF model, utilizing the RossThick-LiSparse kernel functions for characterizing isotropic, volume and surface scattering (Wanner et al., 1995; 1997; Lucht et al., 2000; Schaaf et al., 2002; 2011). A reciprocal version of the LiSparse kernel is employed. When sufficient MODIS (Terra plus Aqua) observations are available to fully characterize the angular viewing/illumination geometry (as signified by the weights of determination), a high quality full inversion can be attempted --- otherwise a low quality magnitude inversion is performed by relying on a priori BRDFs based on recent high quality MODIS retrievals at that location as a first guess and adjusting these by the available observations (Wang et al., 2018).

The BRDF parameters retrieved quantify intrinsic surface properties decoupled from the prevailing atmospheric state and hence are suited for applications requiring characterization of the directional anisotropy of Earth surface reflectance. The parameters are also applicable for the computation of both the directional hemispherical reflectance (black-sky albedo) and the bihemispherical reflectance under isotropic illumination (white-sky albedo). This can be achieved through the use of a simple polynomial (Lucht et al, 2000) although the white-sky and black-sky (at local solar noon) albedo computations are provided as part of the product for user convenience. Blue sky albedo, the actual bihemispherical reflectance at a particular time can be computed as a function of white-sky and black-sky albedo and the aerosol optical depth (Lewis et al, 1994; Roman et al, 2010).  View angle corrected Nadir BRDF-Adjusted Reflectances (NBAR) at local solar noon are also provided to the user community. A complete set of quality control flags accompanies each product and should be utilized by the user. 

For more product details, refer primarily to the MCD43 User Guide, the product specification (V006 and V006.1), the product validation status, Schaaf et al. (2011; 2002), Wang et al., 2012; Lucht et al. (2000), and Wanner et al., (1997) and the more recent publications of the MODIS BRDF/Albedo team.

Follow this link to download MODIS BRDF & Albedo Datasets from the LAADS DAAC.