On the variability of the reflected radiation field due to differing distributions of the irradiation

Abstract The directional reflected radiation of natural surfaces may change even if nothing save the distribution of the irradiation over the hemisphere varies. This is due to the angular anisotropy of the reflection properties of natural surfaces. The quantitative determination of this effect for four different vegetated surfaces is the aim of this investigation. In this paper, results for the first of the four surfaces, a savannah, are shown. The directional reflected radiation may change by ± 1% per degree change of the solar zenith angle and by ± 1 per 6% change of the spectral atmospheric turbidity factor at 0.52 μm.