Eddy covariance theory: A review

Authors: WOOD, JEFFREY - University Of Missouri; GAO, LIANHONG - Oak Ridge National Laboratory; Schreiner-Mcgraw, Adam

Submitted to: Global Change Biology
Publication Type: Review Article
Publication Acceptance Date: 4/27/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Eddy covariance is the gold standard for measuring field scale exchange of gas and heat between the land surface and the atmosphere. This technique relies on measuring turbulence in the air and can be used to simultaneously measure crop growth and water use. Despite numerous methodological improvements and insights gained from the technique, challenges remain in fully leveraging the data due to the complexities involved with measuring turbulence. In this paper, we review the theoretical developments guiding the use of eddy covariance. We present developments in four important areas that have allowed the use of eddy covariance in agricultural settings. But, problems remain in using eddy covariance measurements particularly the relatively high uncertainty of the measurement. To reduce this uncertainty, we identify two aspects of the mathematical theory of eddy covariance that need to be improved and we present a research agenda to accomplish this. These improvements will improve scientists ability to measure crop growth. This will in turn increase scientists ability to measure the effects of genetic and management advances on crop growth. This allows researchers to develop agricultural solutions to increase crop performance and support American farmers.

Technical Abstract: Eddy covariance (EC), the gold standard for measuring ecosystem scale gas and heat exchanges, has transformed our understanding of the breathing of the biosphere, and thus global change biology. Despite numerous methodological improvements and insights gained from the technique, challenges remain in fully leveraging the data due to the complexities inherent to turbulence measurements. In this contribution, we review the theoretical developments underpinning EC. We present theoretical developments in four important areas that have relevance to EC measurements of the net ecosystem exchange (NEE) of gases and heat: i) measuring the total vertical flux, ii) flux attenuation, iii) coordinate rotations, and iv) energy balance closure. Persistent problems with EC measurements, such as the inability to close the energy budget, led us to identify two priorities for revisiting the theory underlying: i) sensible heat flux calculations, and ii) constraining the mean vertical wind velocity. We present a framework for improved calculation of sensible heat flux derived from first principles of fluid mechanics and thermodynamics that considers coupled heat and mass transfer so that conservation of both is obeyed. These refinements are motivated by the need for unbiased measurements of energy and mass transfer between the land surface and atmosphere for ecosystem research and to validate satellite observations and land surface models.