Dynamic mapping of broadband visible albedo of soil background at global 500-m scale from MODIS satellite products

Land surface albedo is considered to be a fundamental quantity for accurate assessment of the surface energy budget. Whereas satellite products usually provide total surface albedo, land surface models and numerous applications often require a separation of snow-free surface albedos of the vegetation canopy and the underlying bare soil. In this paper, a simplified non-linear spectral mixture model (NSM) was firstly presented to describe the canopy radiative transfer process. The soil background’s contribution on canopy albedo was approximated using an illumination factor, which is the canopy transmittance. Then, a framework was designed to retrieve the soil VIS albedo using the NSM model, MODIS BRDF (MCD43A3), leaf area index (LAI) (MCD15A2H) and clumping index (CI) products. Finally, the global broadband visible albedo of soil background was indirectly validated using the ECOCLIMAP data, with an R2 value of 0.889. Therefore, the simplified NSM model is accurate to simulate canopy visible albedo and also to retrieve soil background’s albedo, and the first global snow-free albedo of soil background at 500-m resolution is reliable.