Evaluation of the Effects of Surface Roughness on the Relationship Between Soil BRF Data and Broadband Albedo

This paper reports a preliminary study on correctness of the broadband albedo (α_b) of cultivated soils that could be calculated by their narrowband bidirectional reflectance factors (BRF) measured from many directions with a prototype goniometric device in a laboratory on their samples with similar roughness, as these soils revealed in the field. The correctness was tested on examples of Phaeozem, Luvisol, and Albeluvisol with roughness formed by a plow, disk harrow, pulverizing harrow, and smoothing harrow. The α_b values of the soils calculated using the equation proposed here were not affected by the root mean square error higher than 0.01 as compared to the data measured in the field if the BRF data were obtained on the soil samples with a sufficiently low roughness. It was found that the roughness of those soil samples should be sufficiently low to ensure that the values of their height standard deviation along the length of the minor axis of a sensor field of view area are greater than 15.