A Parameterization of the Evaporation from Nonsaturated Surfaces

Abstract

The parameterization of evaporation proposed by Priestley and Taylor (1972) is modified to take account of nonsaturated surfaces. It is suggested that evaporation can be expressed as a function of net radiation, air temperature, a constant related to the nature of the surface, and a variable that is dependent on moisture availability. The constant is equal to 1.26 for water and open grassland surfaces (as in Priestley and Taylor) but is nearer unity for some other surfaces. The variable is found to be directly related to near-surface soil moisture content for both bare and grassland surfaces.