Dielectric Model of Thawed and Frozen Organic Soil at the AMSR Radiometer Frequency
In this paper, we develop a simple single-frequency dielectric model of thawed and frozen arctic soil for a frequency of 6.9 GHz. The model is developed based on laboratory dielectric measurements of soil samples containing 80–90% organic matter in the range of gravimetric moisture from 0.01 to 0.942 g/g (volumetric moisture ranging from 0.007 to 0.573 cm3/cm3), and temperatures from +25 to –30°C in the freeze mode. A refractive mixture model is used as a regression equation for the measured values of the complex soil refractive index depending on moisture. The complex refractive indices of various soil components (mineral-organic , bound, transitional, and free water (ice for frozen soil)), as well as values for the maximum allowable content of bound and transitional water in the soil at all measured temperatures, are determined using the regression analysis. The empirical dependences of the complex refractive index of soil components and the maximal allowable contents of various types of water in soil on temperature are obtained. As a result, we developed a model that allows calculating the permittivity of thawed and frozen organic soil as a function of moisture and temperature at 6.9 GHz. The root-mean-square error was 0.20 for the real part of the complex dielectric permittivity of the soil and 0.22 for the imaginary part at the determination coefficient values of 0.999 and 0.995, respectively.