Estimation of thermal properties of saturated soils using in-situ temperature measurements

Abstract

Abstract. We describe an approach to find an initial approximation to the thermal properties of soil horizons. This technique approximates thermal conductivity, porosity, unfrozen water content curve in horizons where no direct temperature measurements are available. To determine physical properties of ground material, optimization-based inverse modeling techniques fitting the simulated and measured temperatures are commonly employed. Two major ingredients of these techniques is an algorithm to compute the soil temperature dynamics and a procedure to find an initial approximation to the ground properties. In this article we show how to determine the initial approximation to the physical properties and present a new finite element discretization of the heat equation with phase change to calculate the temperature dynamics in soil. We successfully applied the proposed algorithm to recover the soil properties for Happy Valley site in Alaska using one-year temperature dynamics. The determined initial approximation was utilized to simulate the temperature dynamics over several consecutive years; the difference between simulated and measured temperatures lies within uncertainties of measurements.