Modeling soil thermal conductivities over a wide range of conditions

This paper presents a new method to seamlessly calculate thermal conductivity for various soil conditions, from loose to compact, organic to mineral, fine to coarse textured, frozen to unfrozen, and dry to wet. The soil is considered as a multi-phase system, containing air, water (liquid, ice), and particles finer (organic matter, minerals) and coarser (gravel) than 2 mm. The new method extends the general portability of the earlier Johansen (1975) method, and this generalization was fine-tuned empirically with data from soil, gravel, and peat drawn from recent and older literature, for frozen and unfrozen conditions from -30 to 30 degrees C, and for variable moisture and bulk density conditions from dry to saturated. Scatter plots between measured conductivity and best-fitted calculations consistently followed a straight 1:1 correspondence, with R-2 values generally above 0.90. The new method was then used to re-interpret thermal conductivity data involving wettable and non-wettable soils, in situ field measurements, and snow.