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Measurement of Evaporation by a Vapor Budget Technique
Author(s) -
Sill B. L.,
Fowler J. E.,
Lagarenne W. R.
Publication year - 1984
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr020i001p00147
Subject(s) - fetch , evaporation , water vapor , environmental science , atmospheric sciences , flux (metallurgy) , atmosphere (unit) , meteorology , hydrology (agriculture) , materials science , geology , physics , oceanography , geotechnical engineering , metallurgy
A vapor budget method for measuring evaporation from lakes is described. The technique involves measuring the upwind and downwind horizontal water vapor flux in the atmosphere for air that passes over an exposed water body. The difference in the two fluxes is shown to be equal to the surface evaporation. Instrumentation used to measure the required vertical profiles of horizontal velocity and water vapor density is also described. The method is applied on a small pond (57 × 57 m) in southern California, and measurements are compared with hourly water budget values of evaporation. Despite the short fetch, which limits the thickness of the vapor layer, comparison of the vapor budget values and those obtained by the water budget method is favorable. Results from a limited number of measurements on a larger lake (with a 600‐m fetch) are also presented. It is estimated that at the present state of development, the vapor budget method is accurate to approximately 20% for small‐ to medium‐sized lakes.