Location: Soil and Water Management ResearchTitle: ET measurement and estimation - What we talking about relates to how quality can be controlled
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/18/2020
Publication Date: 11/10/2020
Citation: Evett, S.R., Marek, G.W. 2020. ET measurement and estimation - What we talking about relates to how quality can be controlled [abstract]. 2020 ASA-CSSA-SSSA International Annual Meeting, November 7-11, 2020, Phoenix, AZ (Virtual). Paper No. 124595.
Technical Abstract: Evapotranspiration (ET) is a term for the total of evaporation from plant and soil surfaces and transpiration through plant stomata and surfaces. ET may be measured by mass balance (e.g., weighing lysimeter) or estimated indirectly from direct measurements or sensing of related quantities (e.g., eddy covariance, Bowen ratio, scintillometry methods). Although ET is a rate, the measurements are discrete, so error can be introduced by different lag times for related direct measurements used jointly in an estimation method. The estimation methods each assume some model of the soil-plant-atmosphere continuum (SPAC) and the related measurements can be seen as assimilated data that keep the model on track to a better estimate of ET. The physical completeness of a model and what that model represents are important considerations. All ET methods, whether by direct measurement or estimation, represent some extent of the SPAC in 4-D. Just what is represented is vital to understanding the value and utility of ET data from a given method. Methods for extending the space-time representivity of an ET method are needed given the cost of applying a method. ET data integrity extends to the quality assurance and control methods applied to direct measurements, whether of ET or related quantities used in ET models. ET simulation models represent a second order of indirect ET estimation. Data integrity also extends to the internal integrity of ET simulation models, the choice of model and related input data, and the language we use to describe simulated variables. Imprecise and confused language hampers our ability to remedy problems in ET measurement and estimation.