Evapotranspiration Adjustment Factors in Florida
Publication: Journal of Irrigation and Drainage Engineering
Volume 137, Issue 7
Abstract
Actual evapotranspiration (ET) is commonly estimated at daily time intervals as the product of a crop coefficient and a reference-crop evapotranspiration () that is calculated by using a daily time step. When subdaily time steps are used, crop coefficients must be multiplied by adjustment factors to account for the discrepancy between calculated by using daily and subdaily time steps. These adjustment factors depend on the method used to calculate . By using the ASCE and FAO-56 Penman-Monteith methods with data from several meteorological stations in Florida, the ASCE equation is shown to be preferable for all locations and seasons because it requires the least adjustment to the crop coefficient when 15-min and 1-h time steps are used. The required adjustment factors depend on location and season, are greatest in the summer, and are approximately the same for 15-min and 1-h time steps. A comparative evaluation between daily and values of potential evapotranspiration (PET) provided by three public databases shows that PET estimates should generally not be used as substitutes for , because the relationship between PET and varies significantly with location and season. For all locations and seasons considered in this study, daily agrees most closely with the PET given by the Florida Automated Weather Network.
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Information
Published In
Journal of Irrigation and Drainage Engineering
Volume 137 • Issue 7 • July 2011
Pages: 403 - 411
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Feb 14, 2010
Accepted: Oct 21, 2010
Published online: Oct 28, 2010
Published in print: Jul 1, 2011
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