MODEL COMPARISONS TO SIMULATE SOIL FROST DEPTH

The depth and duration of soil freezing have important implications fo r the hydrology, biology, and chemistry of ecosystems. Four existing s oil models capable of simulating subfreezing soil temperatures and fro st depth were evaluated for their ability to predict the depth and tim ing of soil frost at sites in North America. The evaluation was carrie d out by comparing model simulations with field data collected in Alas ka, characterized by a Cryaquept with grass cover, and in Minnesota, c haracterized by a Haploboroll with corn stubble. The SHAW and SOIL mod els employ a finite difference solution to assess heat now in the soil profile. Both models predicted frost depth with reasonable accuracy, at least when the simulated snow depth agreed with the recorded snow d epth. The Benoit and Gusev models assess frost depth by balancing heat fluxes within the soil profile. These models generally overpredicted frost depth. The chief advantages of the simpler Benoit and Gusev mode ls are the fewer data requirements and faster execution times compared with the SHAW and SOIL models. The latter two models, however, includ e provisions to reduce the data requirements by utilizing default data values in the simulation. The greater accuracy attained using the mor e sophisticated modem computer models may warrant their use for site-s pecific environmental applications. This study illustrates the difficu lty of simulating snow cover, and, therefore, soil frost penetration, accurately.