Dielectric model of a mineral arctic soil thawed and frozen at 0.05–15 GHz

The dielectric model for an arctic soil both thawed and frozen has been developed. The model is based on the soil dielectric measurements carried out in the ranges of gravimetric moisture from 0.01 to 0.43 g/g, dry soil density from 1.25 to 1.83 g/cm
³
, and temperature from 25 to -30°C (cooling run), in the frequency range 0.05-15 GHz. To fit the results of measurements of the soil complex dielectric constant as a function of soil moisture and wave frequency, the refractive mixing dielectric model in conjunction with the Debye multi-relaxation equations were applied. As a result, the spectroscopic parameters of dielectric relaxations for the bound, transient bound, and unbound soil water components were derived, being further complimented with the thermodynamics parameters to ensure a complete set of parameters of the temperature dependent multi-relaxation spectroscopic dielectric model for moist soils proposed. To calculate complex dielectric constant of soil, the following input variables have to be assigned: 1) density of dry soil, 2) gravimetric moisture, 3) wave frequency, and 4) temperature. The error of the dielectric model was evaluated in terms of RMSE, yielding the values RMSE of 0.53 and 0.43 for the soil dielectric constant and loss factor, respectively. These values appeared to be in the order of the dielectric measurement error itself. The dielectric model suggested can be applied in the active and passive remote sensing techniques in microwave to develop algorithms for retrieving soil moisture and freeze/thaw state of the topsoil in the Arctic regions.