Journal ArticleDOI
How Well Can We Measure the Vertical Wind Speed? Implications for Fluxes of Energy and Mass
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TLDR
In this article, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non-orthogonal transducer orientation were estimated for over 100 combinations of angle-of-attack and wind direction using a novel technique to measure the true angle of attack and wind speed within the turbulent atmospheric surface layer.Abstract:
Sonic anemometers are capable of measuring the wind speed in all three dimen- sions at high frequencies (10-50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non- orthogonal transducer orientation were estimated for over 100 combinations of angle-of- attack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the vertical wind speed varied from −5 to 37% for all angles-of-attack and wind directions examined. When applied to eddy-covariance data from three NOAA flux sites, the wind-velocity corrections increased the magnitude of CO2 fluxes, sensible heat fluxes, and latent heat fluxes by ≈11%, with the actual magnitude of flux corrections dependent upon sonic anemometer, surface type, and scalar. A sonic anemometer that uses vertically aligned transducers to measure the vertical wind speed was also tested at four angles-of-attack, and corrections to the ver- tical wind speed measured using this anemometer were within ±1% of zero. Sensible heat fluxes over a forest canopy measured using this anemometer were 15% greater than sensible heat fluxes measured using a sonic anemometer with a non-orthogonal transducer orienta- tion. These results indicate that sensors with a non-orthogonal transducer orientation, which includes the majority of the research-grade three-dimensional sonic anemometers currently in use, should be redesigned to minimize sine errors by measuring the vertical wind speed using one pair of vertically aligned transducers.read more
Citations
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Journal ArticleDOI
Surface-Energy-Balance Closure over Land: A Review
TL;DR: In this paper, the authors provide an overview of the potential reason for the lack of closure of the energy balance closure problem, and address questions with regard to the partitioning of the residual energy balance residual between the sensible and latent fluxes.
Journal ArticleDOI
Towards a consistent eddy-covariance processing: an intercomparison of EddyPro and TK3
Gerardo Fratini,Matthias Mauder +1 more
TL;DR: In this paper, a comparison of two popular eddy-covariance software packages, namely, EddyPro and TK3, is presented, and two approximately 1-month long test data sets were processed, representing typical instrumental setups (i.e., CSAT3/LI-7500 above grassland and Solent R3/ LI-6262 above a forest).
Journal ArticleDOI
On the discrepancy between eddy covariance and lysimetry-based surface flux measurements under strongly advective conditions ☆
Joseph G. Alfieri,William P. Kustas,John H. Prueger,Lawrence E. Hipps,Steven R. Evett,Jeffrey B. Basara,Christopher M. U. Neale,Andrew N. French,Paul D. Colaizzi,Nurit Agam,Michael H. Cosh,José L. Chávez,Terry A. Howell +12 more
TL;DR: In this paper, the authors compared the performance of eddy covariance (EC) and lysimetry (LY), and found that the discrepancy between the two measurements could be in excess of 200 Wm−2 under strongly advective conditions.
Journal ArticleDOI
Correction of a non-orthogonal, three-component sonic anemometer for flow distortion by transducer shadowing
TL;DR: In this article, the authors investigated the dependence of transducer shadowing on sonic path geometry, wind direction and atmospheric stability with simulations that use surface layer data from the Horizontal array Turbulence Study (HATS) field program and canopy roughness-sublayer data from CHATS field program.
Journal ArticleDOI
Underestimates of sensible heat flux due to vertical velocity measurement errors in non-orthogonal sonic anemometers
TL;DR: In this paper, the authors tested whether a non-orthogonal sonic anemometer (CSAT3, Campbell Scientific, Inc.) measures lower vertical wind velocity and sensible heat flux than an orthogonal anemometers (SATI/3Vx, Applied Technologies, Inc.).
References
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Journal ArticleDOI
Correction of flux measurements for density effects due to heat and water vapour transfer
TL;DR: In this article, the basic relationships are discussed in the context of vertical transfer in the lower atmosphere, and the required corrections to the measured flux are derived, where the correction to measurements of water vapour flux will often be only a few per cent but will sometimes exceed 10 percent.
Journal ArticleDOI
FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities
Dennis D. Baldocchi,Eva Falge,Lianhong Gu,Richard J. Olson,David Y. Hollinger,Steven W. Running,P. M. Anthoni,Ch. Bernhofer,Kenneth J. Davis,Robert G. Evans,Jose D. Fuentes,Allen H. Goldstein,Gabriel G. Katul,Beverly E. Law,Xuhui Lee,Yadvinder Malhi,Tilden P. Meyers,William Munger,Walter C. Oechel,Kim Pilegaard,Hans Peter Schmid,Riccardo Valentini,Shashi B. Verma,Timo Vesala,Kell B. Wilson,S. C. Wofsy +25 more
TL;DR: The FLUXNET project as mentioned in this paper is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere.
FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities
Dennis D. Baldocchi,Eva Falge,Lianhong Gu,Richard J. Olson,David Y. Hollinger,Steven W. Running,P. M. Anthoni,Christian Bernhofer,Kenneth J. Davis,Robert G. Evans +9 more
Journal ArticleDOI
Energy balance closure at FLUXNET sites
Kell B. Wilson,Allen H. Goldstein,Eva Falge,Marc Aubinet,Dennis D. Baldocchi,Paul Berbigier,Christian Bernhofer,Reinhart Ceulemans,Han Dolman,Christopher B. Field,Achim Grelle,A. Ibrom,Beverly E. Law,Andrew S. Kowalski,Tilden P. Meyers,John Moncrieff,Russell K. Monson,Walter C. Oechel,John Tenhunen,Riccardo Valentini,Shashi B. Verma +20 more
TL;DR: A comprehensive evaluation of energy balance closure is performed across 22 sites and 50 site-years in FLUXNET, a network of eddy covariance sites measuring long-term carbon and energy fluxes in contrasting ecosystems and climates as mentioned in this paper.
Journal ArticleDOI
Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes
TL;DR: In this paper, the possibility of measuring heat and moisture fluxes using sonic anemometer data is investigated, and theoretical relations for the temperature variance and heat flux are derived.
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