On the variability of the bare soil albedo due to different solar zenith angles and aerosol optical depths

Due to the angular anisotropy of the reflection properties of natural surfaces, bidirectional reflectance factor (BRF) and hemispherical reflectance (albedo) are dependent of solar zenith angle as well as the distribution of hemispheric irradiation. By using the results of Pinty et al. (1989) to describe BRF´s of bare soil in NOAA 7/8 satellite AVHRR band 1 and 2, and the results of LOWTRAN 7 as the description of hemispherical irradiation, the variation of albedo and errors inferring from all viewing directions of BRF under changing solar zenith angles and aerosol optical depths is discussed. This paper also shows that the optimal view angle of bare soil used to infer the albedo from a single observation under solar zenith angle from 25° to 45°, and atmospheric conditions from clear sky to hazy sky for both AVHRR bands is about 50° off-nadir and about 80⁰ relative azimuthal angle. Furthermore, their errors are no more than 1%