Potential evaporation

From Glossary of Meteorology

potential evaporation

(Also called evaporative power, evaporation power, evaporative capacity, evaporation capacity, evaporativity.) A measure of the degree to which the weather or climate of a region is favorable to the process of evaporation.

It is usually considered to be the rate of evaporation, under existing atmospheric conditions, from a surface of water that is chemically pure and has the temperature of the lowest layer of the atmosphere.
See Bowen ratio, relative evaporation.