The estimation of dielectric constant of frozen soil-water mixture at microwave bands

Abstract

The microwave remote sensing is a promising method for detecting the freezing and thawing of soil surface due to change of dielectric constant when frozen. In frozen soil, not all liquid water freezes at or below 0/spl deg/C. Based on the semi-empirical dielectric mixing model for soil water mixture, an extension of model has been made to describe the dielectric constant change of frozen soil as a function of temperature. An empirical function Wu=A/spl middot/|T-273.2|/sup -B/ has been used for estimating the fractions of liquid water and ice in frozen soil, where Wu is unfrozen water content. A and B are parameters related to soil texture, T is temperature in K. The item for calculation of dielectric constant of ice fraction is also added to the semi-empirical mixing model with extension of some related parameters adapted to temperature range below 0/spl deg/C. Thus, with obtaining of liquid water content and ice fraction, the dielectric constant of frozen soil may be estimated. The simulated data shows that the dielectric constant of soil has a sharp change while freezing or thawing occurring. The results could be used for analyzing the characteristics of emission and scattering of soil at microwave frequencies during freezing and thawing.