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Determination of evaporation from integrated profiles of humidity and temperature over an inhomogeneous surface

In this study a moderate-sized alfalfa field was downwind of a large dry region. Measured vertical profiles of temperature, humidity and wind at upwind and downwind sides of the field were used to calculate the short-term evaporation rate, as well as the contribution of horizontally transported or a...

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Bibliographic Details
Published in:Boundary-layer meteorology 1995-08, Vol.75 (3), p.287-299
Main Authors: HIPPS, L. E, ZEHR, D. F
Format: Article
Language:English
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Summary:In this study a moderate-sized alfalfa field was downwind of a large dry region. Measured vertical profiles of temperature, humidity and wind at upwind and downwind sides of the field were used to calculate the short-term evaporation rate, as well as the contribution of horizontally transported or advected heat energy to the evaporation. The vertical profiles must be measured at least to the height at which air is modified by the new surface. In this case that height was as large as 18 m over a several hundred meter long traverse. Evaporation rates calulated by such an approach were in very close agreement to surface fluxes measured by an eddy correlation system near the surface. The difference between calculated and measured values averaged 9.5%. The reduction in sensible heat content of the air of the control volume was substantial during passage over the field. If all this energy was assumed to have been used in evaporation, then the advection of heat contributed from 35 to 86% of the total evaporation rate. It appears that for an inhomogenous surface, knowledge of the distortion of some properties of local boudary layers can yield reliable estimates of local evaporation. The approach has little empiricism as it is based on simple conservation laws.
ISSN:0006-8314
1573-1472
DOI:10.1007/BF00712698