Abstract
It has been commonly observed that soil moisture conditions, in addition to soil chemical components such as organic matters and free iron oxides, complicate the interpretation of soil reflection. Based on the idea that darkening of soils on wetting is attributed to an increase in the average degree of forward scattering, which is caused by changing the medium surrounding soil particles from air to water, a theoretical model was formulated to estimate the effect of soil moisture on soil reflection. This was done by using the delta-Eddington approximation for multiple scattering, together with Mie theory for single scattering. The model contains only one adjustable parameter, a complex refractive index of soil particles. The complex refractive index of soil particles was identified from the observed spectral albedos on both dry and wet surfaces of soils. The imaginary refractive index obtained was highly correlated with the soil chemical properties. Especially, the correlations between the imaginary index and the free iron oxides content were sufficiently higher than those between the spectral albedo and its content, so that the imaginary index would be of some use in estimating free iron oxides content. With the advent of high spectral resolution sensors currently in design for Earth observational remote sensing from space, this result offers promising advancements in the use of multitemporal remotely sensed data, that is, the data collected when both dry and wet for soil studies.
Published Version
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