Skip to main content
ARS Home » Pacific West Area » Davis, California » Crops Pathology and Genetics Research » Research » Publications at this Location » Publication #358074
Title: Comparison of vineyard evapotranspiration estimates from surface renewal using measured and modeled energy balance components in the GRAPEX project

Author
item Parry, Christopher
item Kustas, William - Bill
item Knipper, Kyle
item Anderson, Martha
item Alfieri, Joseph
item Prueger, John
item McElrone, Andrew

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2018
Publication Date: 2/7/2019
Citation: Parry, C.K., Kustas, W.P., Knipper, K.R., Anderson, M.C., Alfieri, J.G., Prueger, J.H., Mcelrone, A.J. 2019. Comparison of vineyard evapotranspiration estimates from surface renewal using measured and modeled energy balance components in the GRAPEX project. Irrigation Science. 37:333-343. https://doi.org/10.1007/s00271-018-00618-y.
DOI: https://doi.org/10.1007/s00271-018-00618-y

Interpretive Summary: Surface renewal (SR) is a biometeorological technique that uses high frequency air temperature measurements above a crop surface to estimate sensible heat flux (H). The H derived from SR is then combined with net radiation (Rn) and ground heat flux (G) measurements to estimate latent heat flux (LE) as the residual of an energy balance equation. Recent advances in SR theory enabled its use beyond research settings, and led to the development of an inexpensive, stand-alone SR system for use in commercial agricultural settings. However, these commercial applications require replacing expensive net radiometers with clear sky models designed to estimate Rn for the energy balance approach while also assuming G is zero on a daily basis. The accuracy of substituting Rn measurements with modeled values is unknown, and the assumption of an inconsequential G requires additional testing. Here, we compare the accuracy of the SR derived estimates of H and LE when Rn is either measured directly or modelled, and we compare results to two eddy covariance (EC) LE observations, namely LE from water vapor EC measurements (LEEC) and LE solved as a residual in the surface energy balance (i.e. LEresid =Rn-G-H). These measurements come from the Grape Remote sensing Atmospheric Profiling & Evapotranspiration eXperiment (GRAPEX) conducted over a vineyard within the Lodi CA wine growing region. LE from SR using tower Rn data measured directly onsite was significantly correlated with LEresid and LEEC with a least squares regression slope ~ 1. LE derived with the modelled SWi and DisALEXI Rn approaches were also correlated with LEresid, but both overestimated LEresid at higher fluxes. Scatter was even greater between LEEC and LE from SR using either modelled or remotely sensed Rn. Incorporating measurements of G had minimal impact on the overall agreement of the various SR approaches and LEEC or LEresid, however in general scatter increased between the SR technique and LEEC. Our results suggest that LE derived from the new SR method requires fairly accurate Rn modelling approaches in order to obtain reliable and unbiased estimates of daily LE in comparison to measured LE using the EC technique.

Technical Abstract: Surface renewal (SR) is a biometeorological technique that uses high frequency air temperature measurements above a crop surface to estimate sensible heat flux (H). The H derived from SR is then combined with net radiation (Rn) and ground heat flux (G) measurements to estimate latent heat flux (LE) as the residual of an energy balance equation. Recent advances in SR theory enabled its use beyond research settings, and led to the development of an inexpensive, stand-alone SR system for use in commercial agricultural settings. However, these commercial applications require replacing expensive net radiometers with clear sky models designed to estimate Rn for the energy balance approach while also assuming G is zero on a daily basis. The accuracy of substituting Rn measurements with modeled values is unknown, and the assumption of an inconsequential G requires additional testing. Here, we compare the accuracy of the SR derived estimates of H and LE when Rn is either measured directly or modelled, and we compare results to two eddy covariance (EC) LE observations, namely LE from water vapor EC measurements (LEEC) and LE solved as a residual in the surface energy balance (i.e. LEresid =Rn-G-H). These measurements come from the Grape Remote sensing Atmospheric Profiling & Evapotranspiration eXperiment (GRAPEX) conducted over a vineyard within the Lodi CA wine growing region. LE from SR using tower Rn data measured directly onsite was significantly correlated with LEresid and LEEC with a least squares regression slope ~ 1. LE derived with the modelled SWi and DisALEXI Rn approaches were also correlated with LEresid, but both overestimated LEresid at higher fluxes. Scatter was even greater between LEEC and LE from SR using either modelled or remotely sensed Rn. Incorporating measurements of G had minimal impact on the overall agreement of the various SR approaches and LEEC or LEresid, however in general scatter increased between the SR technique and LEEC. Our results suggest that LE derived from the new SR method requires fairly accurate Rn modelling approaches in order to obtain reliable and unbiased estimates of daily LE in comparison to measured LE using the EC technique.