The Canadian Land Surface Scheme (CLASS) is a numerical model pioneered at the Canadian Atmospheric Environment Service by Verseghy (1991) and Verseghy et al. (1993) to evaluate the vertical transfer of energy and water between the atmosphere and three surface soil layers. This article introduces SABAE-HW (soil atmosphere boundary, accurate evaluations of heat and water), a new model built using the modeling framework of CLASS version 2.6 that allows a user to specify depth and number of soil layers. The physically based calculations of heat and moisture transfer are adequately extended in the new code to fit the desired refined mesh. The generalized minimal residual (GMRES) iterative method is used to resolve new soil heat flux terms. Moreover, a water table lower boundary condition is added to allow eventual coupling with groundwater models. The results of SABAE-HW are validated for some synthetic runs under real-like seasonal weather conditions and various soil types. Then the model prediction capability is confirmed for a location within the Assiniboine Delta Aquifer using North American Regional Reanalysis (NARR) atmospheric data. Intercomparisons of results to simulation outputs from CLASS, SHAW, HYDRUS-1D, and HELP models demonstrate the capability of SABAE-HW to predict reasonable moisture profiles and water budget terms. Under warm weather conditions, SABAE-HW and SHAW yield similar water content profiles and bottom drainages. Also, in the freezing–thawing situations, detailed moisture profiles by SABAE-HW are contrasted to both CLASS and SHAW solutions.

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