A Physically Based Model of Soil Freezing in Humid Climates Using Air Temperature and Snow Cover Data

Abstract

A one-dimensional heat flow model is developed to estimate depths of soil freezing and thawing using a daily time step. This physically based model assumes near-saturated soil moisture conditions and simulates freezing under bare soil and sod using only those meteorological variables observed at cooperative network stations (i.e., daily temperature, precipitation, and snow depth). Therefore, using this relatively dense observation network, climatological model-derived frost depth statistics can be developed for stations in regions where soil conditions are typically near saturation during the winter. Soil-freezing estimates should be useful in a variety of applications, especially those concerned with agricultural and engineering design specifications. Based on comparisons with measured soil temperature data, the model successfully captures the seasonal progression, rate, and maximum depth of soil freezing and thawing at several climatically diverse locations. Verification results indicate that model-derived maximum frost penetration values were typically within 0.04 m of those observed over a three-winter period at Ithaca, New York. On a daily basis, frost depth estimates were typically within 0.10 m of the observed Ithaca values. The magnitudes of these errors are unaffected by the presence or absence of snow cover and the depth of soil freezing. However, more reliable estimates tend to occur under bare soil than sod. In the case of bare soil, verification analyses indicate a small but consistent bias toward overestimation of the depth of soiling freezing. For sod, a consistent bias could not be identified. This condition may result from representing different, but unreported, sod conditions at various sites with a single fixed parameter.