Retrieval of land surface albedos from satellite measurements

This dissertation discusses a program of research directed to providing a global, monthly Bidirectional Reflectance Distribution Function (BRDF) and albedo dataset at 1 km resolution for use in atmospheric aerosol and global climatological research. BRDF is the quantitative description of the directional properties of a surface, which vary as a function of wavelength and surface structure. Albedo is the integral of BRDF and quantitatively describes the shortwave energy balance at the surface. Both quantities are of interest to researchers in climatology, meteorology and atmospheric physics.; Complex relationships exist between land cover and BRDF and these may be used as a priori information in BRDF retrieval from directional reflectance data. A comparison of such a land cover-constrained retrieval and a conventional, free-inversion retrieval of BRDF and albedo over the KONVEX experimental site demonstrated that the land cover-constrained method produces more accurate BRDF retrievals when observations are limited in number.; After the validation phase, the BRDF and albedo retrieval is applied using existing land cover maps and satellite imagery from NOAA's Advanced Very High Resolution Radiometer instrument. The inversion procedure relies on a many-to-many mapping of land cover classes to BRDF classes dependent on factors such as vegetation senescence and snow cover. Using this procedure, we provide global albedo data for February and July 1995 at 1 and 10 km resolutions.; These data are the first available global 1 km albedo maps which explicitly use both satellite reflectance data and surface-dependent BRDF models, and provide a reference against which NASA's future Earth Observing System Moderate Resolution Imaging Spectroradiometer albedo and BRDF products may be compared. In addition to providing valuable quantitative data, the maps reveal important regional changes in albedo, such as the effects of the Indian Monsoon, the varying effects of snow over forested and treeless land covers and the effects of vegetation senescence in temperate zones.