Parameterization of Surface Evaporation Rate for Use in Numerical Modeling

Abstract

Numerical models require parameterization of surface evaporation rates when a surface energy budget equation is included in the calculation of the surface temperature. Techniques for parameterizing surface moisture and evaporation are reviewed. Two methods in particular are investigated with observational data taken from the Wangara, the O'Neill, the Kerang and the Davis experiments. Method I is based on parameterization of the surface moisture with the surface evaporation computed through the flux-profile similarity relationships. Method II is based on a modified form of the Penman equation which requires a knowledge of solar radiation and soil heat flux to calculate surface evaporation. Comparisons of the results of these methods are made with observations. Method I fails to account for condensation which is often observed during the night. Method II is shown to be superior to Method I in the calculation of surface evaporation for both day and night.