Abstract
This paper deals with an investigation of the mechanism of diurnal variation regarding the albedo of soils.
First, trial equipment for the albedo measurement can be made sure to fulfill its function precisely.
Second, it can be shown qualitatively that the physical and chemical properties of soil and the geometrical features of the soil's surface being composed of different size particles may be the main cause of the diurnal variation concerning albedo.
Finally, the mechanism of the diurnal variation regarding the albedo of the soil is examined, semitheoretically. The albedo of soil versus solar altitudes may be estimated by means of introducing both the hypothetical and analytical methods. Especially, soil particle models that make up the soil's surface may be proposed. Effects of the solar altitude on the models may be attributed mainly to the yield of both shade & shadow and sunny parts on the particles. The diurnal variation of the ratios of both shade & shadow and sunny area fractions to their unit area projected orthogonally to the soil's surface level may be calculated analytically. The estimated albedos may be put on the tendency of the diurnal variation of the measured albedo. On the other hand, it can be explained that the physical and chemical properties of soils might not have a direct influence on the albedo diurnal variation, but have a great influence on the production of great and small values for the variation, and the same thing might hold true for the ratio of direct incident radiation to diffuse radiation.
