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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #297994

Title: Sensitivity analysis of reference evapotranspiration to sensor accuracy

Author
item DeJonge, Kendall
item AHMADI, MEHDI - Colorado State University
item Ascough Ii, James
item KINZLI, KRISTOPH-DIETRI - Florida Gulf Coast University

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2014
Publication Date: 11/15/2014
Citation: DeJonge, K.C., Ahmadi, M., Ascough II, J.C., Kinzli, K.C. 2014. Sensitivity analysis of reference evapotranspiration to sensor accuracy. Computers and Electronics in Agriculture. 110 (2015) 176-186.

Interpretive Summary: Multiyear datasets from the semi-arid Colorado Agricultural Meteorological (CoAgMet) and humid Florida Automated Weather Network (FAWN) networks were evaluated using both local and global sensitivity analysis methods (LSA and GSA, respectively). Sensitivity of inputs (i.e., temperature, humidity, wind speed, and solar radiation) was generally well-balanced for the FAWN network with solar radiation being the most influential input in the summer, while the sensitivity to wind in the CoAgMet network was much higher than the other inputs. LSA is suggested as a basic screening method for evaluating input sensor sensitivity. GSA results were highly correlated with each other, but local sensitivity was poorly correlated for wind input in Colorado.

Technical Abstract: Meteorological sensor networks are often used across agricultural regions to calculate the ASCE Standardized Reference ET Equation, and inaccuracies in individual sensors can lead to inaccuracies in ET estimates. Multiyear datasets from the semi-arid Colorado Agricultural Meteorological (CoAgMet) and humid Florida Automated Weather Network (FAWN) networks were evaluated using a local sensitivity analysis (LSA) method which calculated the total error range of each individual sensor, as well as Morris and eFAST global sensitivity analysis (GSA) methods which simultaneously evaluated the full accuracy range of each sensor. Sensitivity of inputs (i.e., temperature, humidity, wind speed, and solar radiation) generally had values within the same range for the FAWN network with solar radiation being the most influential input in the summer, while sensitivity to wind speed for the CoAgMet network was much higher than the other inputs. Due to its simplicity and ease of application, LSA is suggested as a minimal screening method for evaluating input sensor sensitivity. GSA results were highly correlated with each other, but local sensitivity was poorly correlated to GSA methods regarding wind input in Colorado. Uncertainty analysis showed the current configuration of sensors in the CoAgMet network to have a higher range of values between 5% and 95% confidence intervals, as compared to the FAWN network. The eFAST GSA method was applied using a hypothetical set of “best case” sensors in both stations, showing solar radiation to be the most influential input in the high ET months of summer, and the sensitivity in Colorado to wind to be vastly decreased, suggesting that the CoAgMet network could benefit from an upgrade to more accurate anemometers.