Effects of Soil Roughness on the Optimal Time of Cultivated Soils Observation by Satellites for the Soils Average Diurnal Albedo Approximation

This study explores the diurnal variation, from midday to sunset, in broadband blue-sky albedo (α) of soils with respect to their surface roughness. Five roughness levels of soil surfaces shaped by a plow, spike tooth harrow and roller, then also modified by rain, developed from the same soil material, were examined. The relation between α and the solar zenith angle enabled us to predict in which solar local time for chosen days of year the α of such surfaces, located between the latitude angles of 70° in the Northern and Southern Hemispheres, reaches its average diurnal value [(α)] . The usefulness of remote sensing satellite instruments for [(α)] approximation of the surfaces is evaluated here as the consequences of the difference between the optimal time for their [(α)] approximation and the time when the satellite instruments on the sun-synchronous orbits passing over the surfaces can observe them. Two examples of the orbits: close to that being optimal to the [(α)] approximation like NOAA-15, as well as that most often have been used to the α estimation such as MODIS instrument on the EOS Terra platform are considered.