FIELD TESTING OF SIMULATED SOIL FREEZING AND THAWING BY THE SHAW MODEL

Winter conditions associated with freezing, thawing, and soil moisture changes are important factors for a number of agricultural applicatio ns. In this study, the SHAW (Simultaneous Heat And Water) model was ev aluated on predicting winter conditions (i.e., soil temperature, moist ure content, snow cover, and depth of frost penetration) at a natural show covered site and a site with the snow removed for the winter seas on of 1983-1984. The model successfully estimated the observed snow de pth, the temperature extremes, and changes in total and liquid water c ontent. Observerd maximum frost penetration was 1.02 m while the estim ated was 1.04 m. The root mean square (RMS) difference between simulat ed and measured soil temperature was less-than-or-equal-to 1.5-degrees -C and between simulated and measured volumetric soil water content wa s less-than-or-equal-to 0.04 m3.m-3. The estimated last day with snow cover was within 2 days of the observed date. These results confirm th e usefulness of the SHAW model to simulate these winter conditions.