An investigation of remotely-sensed soil depth in the optical region

Abstract

Abstract. The remotely-sensed soil depth in the visible and near-infrared (near-IR) spectral region is investigated by using a numerical radiative transfer model of the coupled atmosphere and soil media. The sensible depth is determined by examining the downward hemispheric transmittance pro® le, hemispherical re¯ectance, and bidirectional re¯ectance with di V erent solar zenith angles at di V erent wavelengths. The particle size distributions and particle shapes are also evaluated. Under an ordinary condition, the sensible optical depth is about 3, which corresponds to geometric depth of 4± 5 times the particle e V ective radius.

Determining the influential depth for surface reflectance of sediment by BRDF measurements

“…For 0.25-0.5 mm and 0.125-0.25 mm diameter dry and wet ooids, penetration depth is at most 2 mm for 3 colors. These results are in qualitative agreement with radiative transfer calculations of soil that the sensible depth is about 4 times the effective particle radius when particles are much larger than the probing wavelength [6].…”

“…All wetted surfaces are substantially darkened since upon wetting the refractive index contrast between grains and the surrounding medium decreases thus forward scattering increases and accordingly more absorption occurs [6]. The effects of enhanced forward scattering introduced by wetting are shown in Fig 5. We plot the relative difference of wet and dry REFF, i.e.…”

Flood Monitoring Using Satellite-Based RGB Composite Imagery and Refractive Index Retrieval in Visible and Near-Infrared Bands

“…Figure 12 shows the result of part of the surface refractive index using the new combination of RGB 6-5-2bands. Figure 12a,b show the decomposed components of surface reflectivity The real values of the refractive index for dry silica, calcite, soil, pure water, and seawater are 1.48 [86,87], 1.60 [86,88], 1.4 [83], and 1.33 [81], respectively. In this case, the incidence angles of MODIS data range from nadir to 30 • .…”

“…Figure 10 shows the error of polarized reflectivities between the Fresnel equation, the Hong approximation, and the ASH approximation for soil and water in the VIS bands. In this case, the refractive index of the soil at 0.56 µm and water at 0.4 µm is found to ben = 1.405 + 0.01i [83] and n = 1.339 + 1.86 × 10 −9 i [81], respectively. Soil has a relatively larger value for the imaginary part of the refractive index than water in this wavelength.…”

“…The refractive index of soil ranges from 1.39 + 0.0053i to 1.42 + 0.05i [83] in the optical band from 0.5 µm to 1.1 µm. The refractive index of water ranges from 1.339 + 1.86 × 10 −9 i at 0.4 µm, to 1.296 + 2.89 × 10 −9 i at 2.2 µm [81].…”