A refinement of the combination equations for evaporation

Surveys in Geophysics



Most combination equations for evaporation rely on a linear expansion of the saturation vapor-pressure curve around the air temperature. Because the temperature at the surface may differ from this temperature by several degrees, and because the saturation vapor-pressure curve is nonlinear, this approximation leads to a certain degree of error in those evaporation equations. It is possible, however, to introduce higher-order polynomial approximations for the saturation vapor-pressure curve and to derive a family of explicit equations for evaporation, having any desired degree of accuracy. Under the linear approximation, the new family of equations for evaporation reduces, in particular cases, to the combination equations of H. L. Penman (Natural evaporation from open water, bare soil and grass, Proc. R. Soc. London, Ser. A193, 120-145, 1948) and of subsequent workers. Comparison of the linear and quadratic approximations leads to a simple approximate expression for the error associated with the linear case. Equations based on the conventional linear approximation consistently underestimate evaporation, sometimes by a substantial amount. ?? 1991 Kluwer Academic Publishers.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A refinement of the combination equations for evaporation
Series title Surveys in Geophysics
DOI 10.1007/BF01903416
Volume 12
Issue 1-3
Year Published 1991
Language English
Publisher location Kluwer Academic Publishers
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Surveys in Geophysics
First page 145
Last page 154