Quality assessment of BRDF/albedo retrievals in MODIS operational system

We establish the quality of the MODIS BRDF/albedo retrieval process through the use of the Root Mean Squared Error ( RMSE) and Weight of Determination ( WoD). These measures are constructed during the inversion process to quantify the retrieval uncertainties. RMSE provides a deviation indicator of the model-fits while WoD evaluates the confidence of the retrieval from given angular samplings. From a statistical analysis of retrievals over a range of surface types, we establish an upper range of thresholds ( 0.071, 0.097) for high quality RMSE, ( 1.431, 1.848) for WoD of Nadir Reflectance ( assuming a 45 degrees solar zenith angle, ( 2.122, 2.726) for WoD of White Sky Albedo. An investigation of inversions at typical biomes located at different latitude shows the retrievals are stable with respect to random uncertainty variations in the combined MODIS Terra and Aqua observations under the investigated sun-view geometric angular distribution. The acquired ranges suggest improved thresholds should be implemented for future reprocessing versions of the 500m MODIS operational BRDF/albedo system.