Minimizing flow distortion errors in a sonic anemometer

Kaimal, J. C.; Gaynor, J. E.; Zimmerman, H.; Zimmerman, Gary

doi:10.1007/bf00122466

Cited by 58 publications

(43 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The CO2 standard used in ti\e calibration has been replaced twice during tiw study, with an intercomparison between standanis to within 1%. Ilie zero offsets of the mass flow meters used in the calibration are determined every 2-4 days, and the meters are calibrated at least once every year Similar sonic anemometers have been used throughout the study,, with only a modest change in the on-line shadowing correction, providing long-tenn stability of better than 1% (Kaimal et al 1990;H. A. Zimmermaiv personal commtinication).…”

Section: Long-term Predsionmentioning

confidence: 99%

Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy

Goulden

Munger

Fan

et al. 1996

Global Change Biology

1,307

990

View full text Add to dashboard Cite

The turbulent exchanges of CO2 and water vapour between an aggrading deciduous forest in the north‐eastern United States (Harvard Forest) and the atmosphere were measured from 1990 to 1994 using the eddy covariance technique. We present a detailed description of the methods used and a rigorous evaluation of the precision and accuracy of these measurements. We partition the sources of error into three categories: (1) uniform systematic errors are constant and independent of measurement conditions (2) selective systematic errors result when the accuracy of the exchange measurement varies as a function of the physical environment, and (3) sampling uncertainty results when summing an incomplete data set to calculate long‐term exchange. Analysis of the surface energy budget indicates a uniform systematic error in the turbulent exchange measurements of ‐20 to 0%. A comparison of nocturnal eddy flux with chamber measurements indicates a selective systematic underestimation during calm (friction velocity < 0.17 m s−1) nocturnal periods. We describe an approach to correct for this error. The integrated carbon sequestration in 1994 was 2.1 t C ha−1 y−1 with a 90% confidence interval due to sampling uncertainty of ±0.3 t C ha−1 y−1 determined by Monte Carlo simulation. Sampling uncertainty may be reduced by estimating the flux as a function of the physical environment during periods when direct observations are unavailable, and by minimizing the length of intervals without flux data. These analyses lead us to place an overall uncertainty on the annual carbon sequestration in 1994 of ‐0.3 to +0.8 t C ha−1 y−1.

show abstract

Section: Long-term Predsionmentioning

confidence: 99%

Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy

Goulden

Munger

Fan

et al. 1996

Global Change Biology

1,307

990

View full text Add to dashboard Cite

show abstract

“…Wind and temperature were measured with a three-axis sonic anemometer (Applied Technologies, Boulder, Colorado) pointed due west (270ø). The anemometer incorporated online corrections for flow distortion [Kaimal et al, 1990], and the effect of crosswind on the calculation of temperature [Kaimal and Gaynor, 1991 …”

Section: Measurementsmentioning

confidence: 99%

Physiological responses of a black spruce forest to weather

Goulden¹,

Daube²,

Fan³

et al. 1997

J. Geophys. Res.

342

242

View full text Add to dashboard Cite

Abstract. We used eddy covariance to measure the net exchange of CO2 between the atmosphere and a black spruce (Picea mariana) forest in Manitoba for 16,500 hours from March 16, 1994 to October 31, 1996. We then partitioned net exchange into gross photosynthesis and respiration by estimating daytime respiration as a function of temperature, and used these data to define the physiological responses of the forest to weather. The annual rates of gross production and respiration by the forest were both

show abstract

“…Sonics directly measure one, two or three components T. W. Horst (B) · S. R. Semmer · G. Maclean National Center for Atmospheric Research, Boulder, CO, USA e-mail: horst@ucar.edu of the wind vector, as well as the speed of sound and thus the acoustic equivalent of virtual temperature (e.g. Kaimal et al 1990;Kaimal and Gaynor 1991). Three-component sonic anemometers are commonly used to measure fluxes of momentum and virtual temperature and, when combined with fast-response scalar sensors, vertical fluxes of moisture, CO 2 and other atmospheric constituents.…”

Section: Introductionmentioning

confidence: 99%

Correction of a Non-orthogonal, Three-Component Sonic Anemometer for Flow Distortion by Transducer Shadowing

Horst

Semmer

Maclean

2015

Boundary-Layer Meteorol

View full text Add to dashboard Cite

We propose that flow distortion within a non-orthogonal CSAT3 sonic anemometer is primarily due to transducer shadowing, which is caused by wakes in the lee of the acoustic transducers impinging on their measurement paths. The dependence of transducer shadowing on sonic path geometry, wind direction and atmospheric stability is investigated with simulations that use surface-layer data from the Horizontal Array Turbulence Study (HATS) field program and canopy roughness-sublayer data from the CHATS (Canopy HATS) field program. We demonstrate the efficacy of correcting the CSAT3 for transducer shadowing with measurements of its flow distortion in the NCAR wind tunnel, combined with 6 months of data collected in the atmospheric surface layer with adjacent CSAT3 and orthogonal ATI-K sonic anemometers at the NCAR Marshall field site. CSAT3 and ATI-K measurements of the variance of vertical velocity σ 2 w and the vertical flux of sonic temperature agree within 1 % after correction of both sonics for transducer shadowing. Both the simulations of transducer shadowing and the comparison of CSAT3 and ATI-K field data suggest a simple, approximate correction of CSAT3 surface-layer scalar fluxes with an increase on the order of 4-5 %, independent of wind direction and atmospheric stability. We also find that σ w /u * (where u * is the friction velocity) and r uw (the correlation coefficient) calculated with corrected CSAT3 data are insensitive to wind direction and agree closely with known values of these dimensionless variables for neutral stratification, which is evidence for the efficacy of the correction of the horizontal wind components for transducer shadowing as well.

show abstract

Minimizing flow distortion errors in a sonic anemometer

Cited by 58 publications

References 10 publications

Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy

Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy

Physiological responses of a black spruce forest to weather

Correction of a Non-orthogonal, Three-Component Sonic Anemometer for Flow Distortion by Transducer Shadowing

Contact Info

Product

Resources

About