摘要
A soil-vegetation-atmosphere-transfer scheme, which solves the coupled system of the Surface Energy and Water Balance (SEWAB) equations considering partly vegetated surfaces, is presented. In terms of complexity, SEWAB is similar to many other land–surface schemes with respect to the calculation of the turbulent fluxes of sensible and latent heat the latter being based on the one-layer concept for vegetation. Emphasis is put on the description of the soil processes as the link between the atmospheric and hydrologic system. The diffusion equations for heat and moisture are solved semi-implicitly on a multi-layer grid. Surface runoff and baseflow may be calculated as saturation excess runoff as usually done in land–surface schemes for atmospheric models. In addition to this, the variable infiltration capacity (VIC) approach is included alternatively which takes into account the influence of topographic heterogeneities inside a grid cell on surface runoff prediction. Subsurface runoff may also be described by the ARNO conceptualization allowing a gradual increase with soil moisture content. The saturation hydraulic conductivity is a function of depth. SEWAB has been validated with field data from the FIFE experiment and has participated in the PILPS project for intercomparison of land–surface parameterization schemes. SEWAB partitions reasonably well the incoming solar radiation and the precipitation into sensible and latent heat fluxes as well as into runoff and soil moisture storage. The inclusion of a variable infiltration capacity description slightly improves the surface runoff estimation and the timing of the total runoff. Changes in the parameterization of the subsurface runoff production and the drainage show only minor effects.