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Article

Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area

1
Enviro-Ag Engineering, Inc., Artesia, NM 88210, USA
2
Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Daniela Vanella
Atmosphere 2021, 12(2), 281; https://doi.org/10.3390/atmos12020281
Received: 21 December 2020 / Revised: 12 February 2021 / Accepted: 16 February 2021 / Published: 21 February 2021
(This article belongs to the Special Issue Agricultural Microclimate and Irrigation Water Management)
Eddy covariance (EC) systems are being used to measure sensible heat (H) and latent heat (LE) fluxes in order to determine crop water use or evapotranspiration (ET). The reliability of EC measurements depends on meeting certain meteorological assumptions; the most important of such are horizontal homogeneity, stationarity, and non-advective conditions. Over heterogeneous surfaces, the spatial context of the measurement must be known in order to properly interpret the magnitude of the heat flux measurement results. Over the past decades, there has been a proliferation of ‘heat flux source area’ (i.e., footprint) modeling studies, but only a few have explored the accuracy of the models over heterogeneous agricultural land. A composite ET estimate was created by using the estimated footprint weights for an EC system in the upwind corner of four fields and separate ET estimates from each of these fields. Three analytical footprint models were evaluated by comparing the composite ET to the measured ET. All three models performed consistently well, with an average mean bias error (MBE) of about −0.03 mm h−1 (−4.4%) and root mean square error (RMSE) of 0.09 mm h−1 (10.9%). The same three footprint models were then used to adjust the EC-measured ET to account for the fraction of the footprint that extended beyond the field of interest. The effectiveness of the footprint adjustment was determined by comparing the adjusted ET estimates with the lysimetric ET measurements from within the same field. This correction decreased the absolute hourly ET MBE by 8%, and the RMSE by 1%. View Full-Text
Keywords: footprint; eddy covariance method; energy balance closure; weighing lysimeter footprint; eddy covariance method; energy balance closure; weighing lysimeter
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MDPI and ACS Style

Joy, S.L.; Chávez, J.L. Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area. Atmosphere 2021, 12, 281. https://doi.org/10.3390/atmos12020281

AMA Style

Joy SL, Chávez JL. Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area. Atmosphere. 2021; 12(2):281. https://doi.org/10.3390/atmos12020281

Chicago/Turabian Style

Joy, Stuart L., and José L. Chávez. 2021. "Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area" Atmosphere 12, no. 2: 281. https://doi.org/10.3390/atmos12020281

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