Flux Measurement with Conditional Sampling

Businger, J. A.; Oncley, Steven

doi:10.1175/1520-0426(1990)007<0349:fmwcs>2.0.co;2

Cited by 359 publications

(266 citation statements)

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“…In order to obtain reliable estimates of fluxes, a sampling rate of at least 10 Hz is generally used for eddy covariance techniques. However, measurements performed at lower rates than 10 Hz can generate reliable results too (Rinne et al, 2000 andGraus et al, 2006;Businger and Oncley, 1990). 1 Hz eddy covariance, disjunct eddy covariance, 1 Hz eddy covariance and relaxed eddy accumulation (REA) are possible alternatives for the preferred 10 Hz eddy covariance.…”

Section: Simulation Of Alternative Flux Measurement Approachesmentioning

confidence: 99%

“…Next, the measured concentrations are summed and the turbulent flux of the scalar s (F s ) was determined according to Eq. (8): (Businger and Oncley, 1990). The b-value is the correction for the deadband and s the difference between the concentrations in the accumulation reservoirs (Bowling et al, 1999).…”

Section: Simulation Of Alternative Flux Measurement Approachesmentioning

confidence: 99%

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A compact and stable eddy covariance set-up for methane measurements using off-axis integrated cavity output spectroscopy

et al. 2008

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Abstract.A Fast Methane Analyzer (FMA) is assessed for its applicability in a closed path eddy covariance field set-up in a peat meadow. The FMA uses off-axis integrated cavity output spectroscopy combined with a highly specific narrow band laser for the detection of CH 4 and strongly reflective mirrors to obtain a laser path length of 2-20×10 3 m. Statistical testing and a calibration experiment showed high precision (7.8×10 −3 ppb) and accuracy (<0.30%) of the instrument, while no drift was observed. The instrument response time was determined to be 0.10 s. In the field set-up, the FMA is attached to a scroll pump and combined with a 3-axis ultrasonic anemometer and an open path infrared gas analyzer for measurements of carbon dioxide and water vapour. The power-spectra and co-spectra of the instruments were satisfactory for 10 Hz sampling rates.Due to erroneous measurements, spikes and periods of low turbulence the data series consisted for 26% of gaps. Observed CH 4 fluxes consisted mainly of emission, showed a diurnal cycle, but were rather variable over. The average CH 4 emission was 29.7 nmol m −2 s −1 , while the typical maximum CH 4 emission was approximately 80.0 nmol m −2 s −1 and the typical minimum flux was approximately 0.0 nmol m −2 s −1 . The correspondence of the measurements with flux chamber measurements in the footprint was good and the observed CH 4 emission rates were comparable with eddy covariance CH 4 measurements in other peat areas.Additionally, three measurement techniques with lower sampling frequencies were simulated, which might give the possibility to measure CH 4 fluxes without an external pump and save energy. Disjunct eddy covariance appeared to be the most reliable substitute for 10 Hz eddy covariance, while relaxed eddy accumulation gave reliable estimates of the fluxes over periods in the order of days or weeks.

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Section: Simulation Of Alternative Flux Measurement Approachesmentioning

confidence: 99%

Section: Simulation Of Alternative Flux Measurement Approachesmentioning

confidence: 99%

A compact and stable eddy covariance set-up for methane measurements using off-axis integrated cavity output spectroscopy

et al. 2008

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“…While the performance of the AMANDA is suitable for micrometeorological gradient measurements vertical wind speed can easily be determined with a high temporal resolution with sonic anemometer, fast sensors for ambient NH } concentration measurements are not yet available. The relaxed eddy accumulation technique (REA) overcomes the need of a fast concentration measurement by sampling gases at a constant rate during up and down droughts which are fed to separate reservoirs during the measurement period (Businger and Oncley, 1990). The #ux is then provided as…”

Section: Gradient System and Reamentioning

confidence: 99%

Instrument development and application in studies and monitoring of ambient ammonia

Erisman

2001

Atmospheric Environment

184

108

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During recent years, it has become clear that ammonia is an important gas in relation to di!erent environmental issues, such as acidi"cation, eutrophication, human health and climate change (through particle formation). Therefore, there is a growing need to develop and apply instrumentation suitable for research into emission, dispersion, conversion and deposition of ammonia and ammonium. Recently, several instruments were developed suitable for measuring concentrations in ambient conditions even at very low levels, such as ammonia sensors suitable for monitoring and research, deposition measuring systems and aerosol samplers for on-line measurement of aerosol composition. These instruments have been tested and applied in a number of "eld studies. These studies include dry deposition measurements, ammonium nitrate studies in relation to the (in)direct aerosol e!ect, emission studies and policy evaluation with concentration and deposition monitoring data. The policy evaluation study showed that the measures to reduce ammonia emissions were not as successful as projected beforehand by statistical studies.

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“…According to Businger and Oncley (1990), temperature and methane concentration fluxes can be calculated using the REA method as follows:…”

Section: Relaxed Eddy Accumulation Methodsmentioning

confidence: 99%

“…The relaxed eddy accumulation (REA) method is a theoretically simple micrometeorological technique in which fluxes are measured using the vertical wind velocity and a conditional sampling of updraft and downdraft air (Businger and Oncley 1990). Because this method does not required a gas analyzer with a rapid response, unlike the EC method, it has begun to attract considerable attention for use in studies of trace gas fluxes (Simpson et al 1997;Nemitz et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method

Ueyama

Hamotani

Nishimura

et al. 2012

Theor Appl Climatol

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We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO 2 fluxes measured by the eddy covariance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of halfhourly methane flux measurements to be approximately 1.2 and 0.7 μg CH 4 m −2 s −1 , respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21 μg CH 4 m −2 s −1 on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835±175 mg CH 4 m −2 year −1 (8.35 kg CH 4 ha −1 year −1 ), which was comparable to the flux range of 379-2,478 mg CH 4 m −2 year −1 previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.

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Flux Measurement with Conditional Sampling

Cited by 359 publications

References 0 publications

A compact and stable eddy covariance set-up for methane measurements using off-axis integrated cavity output spectroscopy

A compact and stable eddy covariance set-up for methane measurements using off-axis integrated cavity output spectroscopy

Instrument development and application in studies and monitoring of ambient ammonia

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method

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