A heat balance model for partially vegetated surfaces

Abstract

A steady-state thermal balance model has been designed to enable the prediction of the radiative temperature of partially vegetated surfaces. Vegetation is assumed to be a horizontally homogeneous but porous layer partially covering a soil surface. Short-wave and long-wave energy fluxes absorbed within the vegetation are estimated by solving simplified radiation equations. Sensible and latent heat exchange is estimated using a logarithmic and linear wind profile above the vegetation and a modified exponential profile within the vegetation. The stomatal resistance for latent heat flux is estimated from the equation summarizing the effect of solar irradiance, air temperature, and vapor pressure deficit on stomatal conductance. Based on the energy balance and the heat fluxes and water vapor continuity in the soil-vegetation-atmosphere system, the temperature of the foliage elements and the soil underneath is determined. The model has been tested by comparing simulated radiative temperatures with observed data gathered in short grass and a wheat field. The simulated and measured results match reasonably well. In order to examine whether the model responds to the change of a specific weather or material parameter, a sensitivity analysis of the model is considered.