Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

Translating Wind Speed Measured over Alfalfa for Use in the ASCE Standardized Reference ET Equation

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  5th National Decennial Irrigation Conference Proceedings, 5-8 December 2010, Phoenix Convention Center, Phoenix, Arizona USA  IRR10-8725.(doi:10.13031/2013.35826)
Authors:   Thomas W Ley, Richard G Allen, Marvin E Jensen
Keywords:   ASCE Standardized Reference Evapotranspiration Equation, Reference ET, wind speed, agricultural weather station

Weather station wind speed data for use in the ASCE Standardized Reference Evapotranspiration Equation are expected to represent that occurring at a height of 2 m over and downwind of a smooth measurement surface such as clipped grass. Many agricultural weather stations used for evapotranspiration estimation may not meet such siting conditions for all or part of the growing season. A physically-based approach to adjust wind speeds at various heights and various weather measurement surface conditions to equivalent wind speed at 2 m height over clipped grass is tested. Wind speeds were simultaneously measured during the 2008 and 2009 growing seasons at 2-m and 3-m heights above ground surface over and downwind of variable height alfalfa in several southeast Colorado locations. These wind speed measurements were translated to estimated wind speed at 2 m over grass, and compared. The effects on computed reference evapotranspiration are illustrated and discussed. The results have important consequences in determination of the State of Colorados compliance with the Arkansas River Compact.

(Download PDF)    (Export to EndNotes)