Natural evaporation from open water, bare soil and grass

A - Papers appearing in refereed journals

Penman, H. L. 1948. Natural evaporation from open water, bare soil and grass. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 193 (1032), pp. 120-145. https://doi.org/10.1098/rspa.1948.0037

AuthorsPenman, H. L.
Abstract

Two theoretical approaches to evaporation from saturated surfaces are outlined, the first being on an aerodynamic basis in which evaporation is regarded as due to turbulent transport of vapour by a process of eddy diffusion, and the second being on an energy basis in which evaporation is regarded as one of the ways of degrading incoming radiation. Neither approach is new, but a combination is suggested that eliminates the parameter measured with most difficulty—surface temperature—and provides for the first time an opportunity to make theoretical estimates of evaporation rates from standard meteorological data, estimates that can be retrospective. Experimental work to test these theories shows that the aerodynamic approach is not adequate and an empirical expression, previously obtained in America, is a better description of evaporation from open water. The energy balance is found to be quite successful. Evaporation rates from wet bare soil and from turf with an adequate supply of water are obtained as fractions of that from open water, the fraction for turf showing a seasonal change attributed to the annual cycle of length of daylight. Finally, the experimental results are applied to data published elsewhere and it is shown that a satisfactory account can be given of open water evaporation at four widely spaced sites in America and Europe, the results for bare soil receive a reasonable check in India, and application of the results for turf shows good agreement with estimates of evaporation from catchment areas in the British Isles.

KeywordsRRES175; 175_Meteorology; 175_Soil science
Year of Publication1948
JournalProceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Journal citation193 (1032), pp. 120-145
Digital Object Identifier (DOI)https://doi.org/10.1098/rspa.1948.0037
Open accessPublished as non-open access
PublisherRoyal Society Publishing
ISSN1364-5021

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