Effects of Soil Surface Irregularities on the Diurnal Variation of Soil Broadband Blue-Sky Albedo

Abstract

This paper quantitatively explores, in terms of roughness indices, the effect of soil surface irregularities on the diurnal variation of the broadband blue-sky albedo of a large range of soil properties. Field studies were carried out on cultivated and uncultivated soil surfaces in Poland and Israel that vary in roughness and brightness. It was found that these irregularities, formed by different agricultural equipment and modified by rain or sprinkler irrigation, can be quantified by two roughness indices. Soil roughness not only affects the overall level of the diurnal variation of the albedo, but also affects the intensity of the diurnal increase from the solar zenith angle (µ ) at the local noon to about 75 80 . The roughness indices are variables that precisely determine only the albedo at the local solar noon of soils with the same color value. If the contents of soil organic carbon (SOC) and calcium carbonate are treated as the dominant variables, combined with one of the indices, these three variables together would significantly describe the albedo at the local solar noon of all soil surfaces. The soils, with their high irregularities, showed almost no rising values of albedo at a µ lower than 75 , while the smooth soil surfaces exhibited a gradual increase of the albedo at these angles. It is concluded that the roughness indices provide sufficient means to accurately describe the diurnal variation of the albedo of a wide range of surfaces, disregarding other soil properties.Index Terms-Diurnal albedo variation, field measurements, soil albedo, soils in Poland and Israel, soil surface roughness.

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

“…In our case, the gaps in the α b F data sets resulted from the need to reject those data measured when cirrus clouds obscured the sun. The soil blue-sky albedo measurements carried out in Poland and Israel [23], also confirmed by the data generated using a hemispherical-directional model [24], indicate that the blue-sky α b of extremely rough soil surfaces rises slightly from θ s at local noon to about 75 • -80 • of the θ s , while the α b of smooth soils clearly increases throughout the θ s range. Assuming that such behavior of the soil albedo with respect to the θ s is correct, the data representing a decrease in the α b F with increasing θ s were considered incorrect.…”

Evaporation from Wavy Porous Surfaces into Turbulent Airflows

“…We distinguish between surface roughness that refers to microrelief of soil surfaces due to variations and arrangement of soil aggregates (Lehrsch et al 1987;Guzha 2004) from the general relief of a surface that represents topographical structures that are many times larger than soil aggregates. Studies of heat and mass transfer from terrestrial surfaces have shown that land relief and surface roughness may affect the surface reflectively (albedo) hence the amount of shortwave radiation absorbed at the surface (Bowers and Hanks 1965;Potter et al 1987;Raupach and Finnigan 1997;Matthias et al 2000;Cierniewski et al 2014). Surface roughness and relief have also been shown to act as momentum sinks for the atmospheric flows (Raupach 1992) affecting the aerodynamic boundary layer and turbulent interactions adjacent to the surface (Perry et al 1969;Taylor and Gent 1974;Finnigan 1988;Wieringa 1993;Raupach and Finnigan 1997).…”

Shortwave Radiation Affected by Agricultural Practices

“…The higher the diffuse light ratio, the smaller the impact of θ s on the albedo. Cierniewski et al [16] analysed the diurnal albedo variations of soils to find that soil roughness affected not only the overall level of those variations, but also that the intensity of its increase from θ s at the local noon, to about 75 • -80 • . Surfaces of rough and deep ploughed soils showed almost no rise in albedo values at θ s lower than 75 • , while the same soil, but smoothed, exhibited a gradual albedo increase at these angles.…”