Estimation of the diurnal variation of potential evaporation from a wet bare soil surface

Potential evaporation from a wet bare soil field was measured with a large sensitive weighing lysimeter on a 20 min time step for 5 days at Davis, California. The diurnal evaporation rate modeled with the Penman-Brutsaert model for potential evaporation with atmospheric stability corrections resulted in the best description of the measured fluxes. The Priestley-Taylor model was accurate for short intervals except when conditions of minimal advection were exceeded during the day. It was noted that the Priestley-Taylor formulation with α = 1.26 performs best under unstable atmospheric conditions. During stable conditions, the value of α = 1.26 underpredicts the measured potential evaporation. The advection-aridity model for actual evaporation based on the Bouchet complementary relationship was studied. Strong advection explains the tendency found in other experimental studies to underpredict daily potential evaporation. A methodology to account for the excess advection is discussed in the complementary model, and the flux predictions were equivalent to the Penman-Brutsaert formulation for wet surfaces.