Relation between equilbrium evaporation and the saturation pressure budget

The limiting surface Bowen ratios are calculated which maintain mixed-layer saturation pressure and relative humidity, both with and without boundary-layer entrainment. The equations are formally the same as those of Culf (1994) for equilibrium evaporation, but differ numerically because the coefficients are calculated at the mixed-layer saturation temperature (at the lifting condensation level) rather than at the surface temperature. The diurnal cycle over land is used to illustrate the value of these constraints.