Combined Diagram: A Graphical Representation of Combination Evaporation Rates

Abstract

ombination methods estimate the partition of sensible and latent heat fluxes at the surface by combining the surface energy balance equation with the transfer equations for temperature and water vapor in the atmospheric surface layer. This paper presents a diagram that graphically depicts the main assumptions and steps of the method. Potential, apparent potential, and actual evaporation rates are visually explained with the diagram. Using a linearized saturation water content relation, the diagram permits the derivation of many of the combination evaporation results by means of geometrical analysis. The diagram should be helpful in the teaching and understanding of the combination methodology.