A novel ground-based experimental observation method for determining multiband microwave radiative properties of forest litter

Abstract

ABSTRACTThe layer of litter covering the forest floor attenuates microwave radiation coming from soil. In satellite remote-sensing data, this reduces the sensitivity of brightness temperature to land surface parameters (e.g. soil moisture, snow depth, and snow water equivalent), resulting in poorer inversion accuracy. To quantify the effects of microwave radiative properties of litter at different frequencies, and especially the impact on transmissivity, a novel approach was developed for modelling radiative transfer (RT) through litter. This approach is based on a zero-order RT model that accounts for scattering effects (the τ–ω model, τ is the optical thickness; ω is the single scattering albedo). Controlled ground-based experiments were conducted to obtain brightness temperatures at several frequencies (1.4, 18.7, and 36.5 GHz) as affected by the thickness and weight moisture content of the litter. The effects of measurement errors on transmissivity were then evaluated. This novel method, which is not only based on sound theory but also prevents calibration errors, can be used to obtain parameters such as the extinction coefficient and transmissivity. The results of this study provide new insights into the microwave RT theory of forest systems, allowing for more appropriate brightness temperatures corrections for satellites data, and providing a guide for controlled experiments.