A Kolmogorov-Brutsaert structure function model for evaporation into a turbulent atmosphere

Abstract

In 1965, Brutsaert proposed a model that predicted mean evaporation rate Ē from rough surfaces to scale with the 3/4 power law of the friction velocity (u*) and the square-root of molecular diffusivity (Dm) for water vapor. In arriving at these results, a number of assumptions were made regarding the surface renewal rate describing the contact durations between eddies and the evaporating surface, the diffusional mass process from the surface into eddies, and the cascade of turbulent kinetic energy sustaining the eddy renewal process itself. The working hypothesis explored here is that Ē∼√Dmu*3/4 is a direct outcome of the Kolmogorov scaling for inertial subrange eddies modified to include viscous cutoff thereby bypassing the need for a surface renewal assumption. It is demonstrated that Brutsaert's model for Ē may be more general than its original derivation implied.