Boundary Subroutine for the NCAR Global Climate Model

This report summarizes the parameterizations of surface processes currently being used in the NCAR grid point GCM. It treats in particular: (i) the calculation of ground, snow or sea ice surface temperature in response to net surface heating and depending on soil or snow heat capacity and thermal conductivity; (ii) the calculation of soil moisture, evaporation, surface and groundwater runoff; (iii) the specification of vegetation cover in terms of fractional ground shading, relative area of transpiring and nontranspiring plant surfaces, and land use type; (iv) the surface albedo in terms of soil moisture, vegetation cover, and snow cover, including the shading of snow by vegetation; (v) the plant water budget including dew, intercepted precipitation and transpiration as limited by stomatal resistance and soil dryness; (vi) surface drag coefficients as a function of bulk Richardson number and vegetation cover; (vii) the determination of foliage temperature in response to energy balance requirements and consequent fluxes of heat and moisture from the foliage to canopy air.