Temperature-Dependent Spectroscopic Dielectric Model at 0.05-16 GHz for a Thawed and Frozen Alaskan Organic Soil

A dielectric model for thawed and frozen Arctic organic-rich soil (90% organic matter) has been developed. The model is based on soil dielectric measurements that were collected over ranges of gravimetric moisture from 0.01 to 0.94 g/g, dry soil density from 0.56 to 0.67 g/cm³, and temperature from 25°C to − 30°C (cooling run) in the frequency range of 0.05–16 GHz. The refractive mixing dielectric model was applied with the Debye multirelaxation equations to fit the measurements of the soil's complex dielectric constant (CDC) as a function of soil moisture and wave frequency. The spectroscopic parameters of the dielectric relaxations for the bound, transient bound, and unbound soil water components were derived and were complimented by the thermodynamic parameters to obtain a complete set of parameters for the proposed temperature-dependent multirelaxation spectroscopic dielectric model for moist soils. To calculate the CDC of the soil, the following input variables must be assigned: (1) density of dry soil, (2) gravimetric moisture, (3) wave frequency, and (4) temperature. The error of the dielectric model was evaluated and yielded root mean square error values of 0.266 and 0.214 for the soil dielectric constant and the loss factor, respectively. These values are on the order of the dielectric measurement error itself. The proposed dielectric model can be applied in active and passive microwave remote sensing techniques to develop algorithms for retrieving the soil moisture and the freeze/thaw state of organic-rich topsoil in the Arctic regions.