Internal Consistency of the Bowen Ratio Approach to Flux Estimation Over Forested Wetland

Abstract

Recent experimental evidence over forests indicates that, due to surface effects, turbulent transfer coefficients for momentum and sensible heat exchange differ in a manner which is not predicted by the familiar diabatic influence functions. The question arises as to whether surface influences can also cause differences between the sensible and latent heat exchange coefficients, thus invalidating the Bowen ratio approach to water loss estimation over forests. The matter was examined by evaluating the Bowen ratio at three positions above the canopy of a forested wetland to see if systematic differences might be found between values obtained at different levels. Differences were found which appeared to be consistent with a radiatively controlled variation in zero-plane displacement or source location for sensible heat. However, the relationship does not appear to be particularly strong, nor do Bowen ratios obtained at different heights above the ground disagree sufficiently to justify modification or abandonment of the procedure in its present form.