ABSTRACT
The evaporation of water from land surfaces and from vegetation is a process of profound importance for agriculture, ecology, and geophysics, mechanisms governing the process remained obscure in the history of science. The review of evaporation model opens with a brief description of C. W. Thornthwaite's formula but deals mainly with developments from the theoretical base established by M. I. Budyko and H. L. Penman. Thornthwaite proposed a completely different solution to the problem of estimating evaporation from watersheds in the United States, given minimal climate records. Like Penman, he argued that evaporation was driven primarily by energy available from radiation, but, for the practical reason that very few measurements of radiation were available, he used air temperature as a surrogate variable. Penman developed a mechanistic model for evaporation from free water surfaces and extended it empirically to bare soil and grass.
