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Title: Correcting eddy-covariance flux underestimates over a grassland.

Abstract

Independent measurements of the major energy balance flux components are not often consistent with the principle of conservation of energy. This is referred to as a lack of closure of the surface energy balance. Most results in the literature have shown the sum of sensible and latent heat fluxes measured by eddy covariance to be less than the difference between net radiation and soil heat fluxes. This under-measurement of sensible and latent heat fluxes by eddy-covariance instruments has occurred in numerous field experiments and among many different manufacturers of instruments. Four eddy-covariance systems consisting of the same models of instruments were set up side-by-side during the Southern Great Plains 1997 Hydrology Experiment and all systems under-measured fluxes by similar amounts. One of these eddy-covariance systems was collocated with three other types of eddy-covariance systems at different sites; all of these systems under-measured the sensible and latent-heat fluxes. The net radiometers and soil heat flux plates used in conjunction with the eddy-covariance systems were calibrated independently and measurements of net radiation and soil heat flux showed little scatter for various sites. The 10% absolute uncertainty in available energy measurements was considerably smaller than the systematic closure problem in the surface energymore » budget, which varied from 10 to 30%. When available-energy measurement errors are known and modest, eddy-covariance measurements of sensible and latent heat fluxes should be adjusted for closure. Although the preferred method of energy balance closure is to maintain the Bowen-ratio, the method for obtaining closure appears to be less important than assuring that eddy-covariance measurements are consistent with conservation of energy. Based on numerous measurements over a sorghum canopy, carbon dioxide fluxes, which are measured by eddy covariance, are underestimated by the same factor as eddy covariance evaporation measurements when energy balance closure is not achieved.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); National Aeronautic and Space Administration (NASA); USDA
OSTI Identifier:
942842
Report Number(s):
ANL/ER/JA-35183
Journal ID: ISSN 0168-1923; TRN: US200923%%636
DOE Contract Number:  
DE-AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Agricult. For. Meteor.
Additional Journal Information:
Journal Volume: 103; Journal Issue: 3 ; Jun. 8, 2000; Journal ID: ISSN 0168-1923
Country of Publication:
United States
Language:
ENGLISH
Subject:
54 ENVIRONMENTAL SCIENCES; CARBON DIOXIDE; ENERGY; ENERGY BALANCE; ERRORS; EVAPORATION; HEAT; HEAT FLUX; HYDROLOGY; PLATES; RADIATIONS; RADIOMETERS; RANGELANDS; SOILS; SORGHUM; SURFACE ENERGY; USA

Citation Formats

Twine, T. E., Kustas, W. P., Norman, J. M., Cook, D. R., Houser, P. R., Meyers, T. P., Prueger, J. H., Starks, P. J., Wesely, M. L., Environmental Research, Univ. of Wisconsin at Madison, DOE, National Aeronautics and Space Administration, and National Oceanic and Atmospheric Administrationoratory. Correcting eddy-covariance flux underestimates over a grassland.. United States: N. p., 2000. Web. doi:10.1016/S0168-1923(00)00123-4.
Twine, T. E., Kustas, W. P., Norman, J. M., Cook, D. R., Houser, P. R., Meyers, T. P., Prueger, J. H., Starks, P. J., Wesely, M. L., Environmental Research, Univ. of Wisconsin at Madison, DOE, National Aeronautics and Space Administration, & National Oceanic and Atmospheric Administrationoratory. Correcting eddy-covariance flux underestimates over a grassland.. United States. doi:10.1016/S0168-1923(00)00123-4.
Twine, T. E., Kustas, W. P., Norman, J. M., Cook, D. R., Houser, P. R., Meyers, T. P., Prueger, J. H., Starks, P. J., Wesely, M. L., Environmental Research, Univ. of Wisconsin at Madison, DOE, National Aeronautics and Space Administration, and National Oceanic and Atmospheric Administrationoratory. Thu . "Correcting eddy-covariance flux underestimates over a grassland.". United States. doi:10.1016/S0168-1923(00)00123-4.
@article{osti_942842,
title = {Correcting eddy-covariance flux underestimates over a grassland.},
author = {Twine, T. E. and Kustas, W. P. and Norman, J. M. and Cook, D. R. and Houser, P. R. and Meyers, T. P. and Prueger, J. H. and Starks, P. J. and Wesely, M. L. and Environmental Research and Univ. of Wisconsin at Madison and DOE and National Aeronautics and Space Administration and National Oceanic and Atmospheric Administrationoratory},
abstractNote = {Independent measurements of the major energy balance flux components are not often consistent with the principle of conservation of energy. This is referred to as a lack of closure of the surface energy balance. Most results in the literature have shown the sum of sensible and latent heat fluxes measured by eddy covariance to be less than the difference between net radiation and soil heat fluxes. This under-measurement of sensible and latent heat fluxes by eddy-covariance instruments has occurred in numerous field experiments and among many different manufacturers of instruments. Four eddy-covariance systems consisting of the same models of instruments were set up side-by-side during the Southern Great Plains 1997 Hydrology Experiment and all systems under-measured fluxes by similar amounts. One of these eddy-covariance systems was collocated with three other types of eddy-covariance systems at different sites; all of these systems under-measured the sensible and latent-heat fluxes. The net radiometers and soil heat flux plates used in conjunction with the eddy-covariance systems were calibrated independently and measurements of net radiation and soil heat flux showed little scatter for various sites. The 10% absolute uncertainty in available energy measurements was considerably smaller than the systematic closure problem in the surface energy budget, which varied from 10 to 30%. When available-energy measurement errors are known and modest, eddy-covariance measurements of sensible and latent heat fluxes should be adjusted for closure. Although the preferred method of energy balance closure is to maintain the Bowen-ratio, the method for obtaining closure appears to be less important than assuring that eddy-covariance measurements are consistent with conservation of energy. Based on numerous measurements over a sorghum canopy, carbon dioxide fluxes, which are measured by eddy covariance, are underestimated by the same factor as eddy covariance evaporation measurements when energy balance closure is not achieved.},
doi = {10.1016/S0168-1923(00)00123-4},
journal = {Agricult. For. Meteor.},
issn = {0168-1923},
number = 3 ; Jun. 8, 2000,
volume = 103,
place = {United States},
year = {2000},
month = {6}
}