SWAHP: A Soil Water and Heat Parameterization

Abstract

SWAHP is an efficient algorithm for prediction of moisture and heat fluxes across a bare soil surface. Surface moisture flux is calculated using the time compression assumption in conjunction with special solutions of the nonlinear moisture diffusion equation. Effects of water vapor and hysteresis are incorporated. The average moisture concentration near the surface is calculated continuously, and redistribution is considered. Potential evaporation is calculated using the surface temperature given by the force-restore procedure. SWAHP has been programmed in Fortran for computer solution, and the program is documented in detail. Required input consists of soil physical properties and atmospheric forcing data.