Evaporation Sources and Apparent Diffusivities in a Forest Canopy

Abstract

An energy balance technique for computing fluxes and diffusivities within crop canopies is described. The technique was used in an investigation of the vertical variation of evaporation sources and diffusivities in the canopy of a pine forest. Evaporation sources were found to be fairly evenly distributed over the depth of the canopy, their vertical distribution and relative strengths corresponding roughly to the foliage distribution. Diffusivities decreased rapidly within the canopy, with the sharpest decline occurring at the top of the foliage. The results suggested that even with light winds, transfer processes within the canopy are turbulent in nature and that the level of turbulence is probably associated with momentum transfer.