Soil freezing is an integral part of winter weather in mid- and high- latitudes across the globe and has a profound effect on commerce, particularly construction. In the U. S., construction specifications for foundations and footings tend to be conservative and illogically variable from one municipality to the next. In previous work to provide a standard for determining building codes, a frost depth model which calculates frost depth penetration into a nearly saturated soil using densely available cooperative network data was devised. The nearly-saturated soil assumption is valid during winter in the northeastern United States; however, in more arid regions, soil moisture is often far less than saturation during winter months. The ultimate goal of this research is to devise a viable way to account for moisture variability in western U. S. soils and ultimately formulate a national climatology of soil freezing extremes.
This study explores the issues related to including temporal soil moisture variability in frost depth calculations through the use of existing models. Limited availability of observed soil freezing data in arid regions of the U. S. has required the use of the detailed SHAW Model use as a ground-truthing tool. Although state-of-the-art in its modeling of frost depth penetration, meteorological data requirements are such that this model can only be used at a small number of specially -instrumented weather observing sites across the U. S. Current study has included running both the Northeast and SHAW models while varying the soil water content under fixed soil and atmospheric conditions. Thus far, results have shown a strong correlation between water content, bulk density and the penetration of the zero-degree isotherm in the soil. Should the runs using our current model fail in properly calculating sub-saturated soil frost depths, a function for accurately describing sub-saturated frost penetration will be developed.