Tools for quality assessment of surface-based flux measurements

Foken, T.; Wichura, Bodo

doi:10.1016/0168-1923(95)02248-1

Cited by 1,474 publications

(1,173 citation statements)

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“…It is however questionable whether the method used can adequately separate the turbulent signal from the instrumental noise in the case of the G2311-f for which the overall noise level was very small. For comparison, the standard deviations (Foken and Wichura, 1996). Flag 0 (flux stationarity below 0.3) corresponds to the highest quality, flag 1 (flux stationarity between 0.3 and 1) to medium quality and flag 2 to the lowest quality (flux stationarity above 1).…”

Section: Random Errors and Instrumental Noisementioning

confidence: 99%

“…This threshold was used for all CH 4 fluxes. The fluxes were distributed into three quality classes based on a flux stationarity test (Foken and Wichura, 1996). If the test yielded values smaller than 0.3, the fluxes were given quality flag 0 (highest quality), fluxes with test values between 0.3 and 1 were given flag 1 (medium quality) and if the test yielded values above 1, then the fluxes were flagged with 2 (low quality).…”

Section: Flux Data Filtering and Quality Controlmentioning

confidence: 99%

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Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

et al. 2014

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Abstract. The performance of eight fast-response methane (CH 4 ) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying turbulent conditions. The moderate CH 4 fluxes observed at the location, of the order of 25 nmol m −2 s −1 , provided a suitable signal for testing the instruments' performance.Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ringdown spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH 4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H 2 O concentrations alongside CH 4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H 2 O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH 4 fluxes. Following this procedure we estimated a bias of the order of 0.1 g (CH 4 ) m −2 (8 % of the measured mean flux) in the processed and corrected CH 4 fluxes on a monthly scale due to missing H 2 O concentration measurements. Finally, cumulative CH 4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc.), FGGA (Los Gatos Research) and FMA2 (Los Gatos Research), which were measuring H 2 O concentrations in addition to CH 4 , agreed within 3 % (355-367 mg (CH 4 ) m −2 ) and were not clearly different from each other, whereas the other instruments derived total fluxes which showed small but distinct differences (±10 %, 330-399 mg (CH 4 ) m −2 ).Published by Copernicus Publications on behalf of the European Geosciences Union. 3164O. Peltola et al.: Evaluating the performance of gas analysers for CH 4 EC flux measurements

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Section: Random Errors and Instrumental Noisementioning

confidence: 99%

Section: Flux Data Filtering and Quality Controlmentioning

confidence: 99%

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

et al. 2014

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“…The third part of the program performs a planar fit coordinate rotation (Wilczak et al 2001), correction of spectral loss (Moore 1986), and conversion of buoyancy into sensible heat flux (Schotanus et al 1983;Liu et al 2001). Lastly, a post-field quality control (Rebmann et al 2005), a steady state test (Foken and Wichura 1996) and a test for integral turbulence characteristics (Foken and Wichura 1996;Thomas and Foken 2002) were performed.…”

Section: Field Observation and Data Processingmentioning

confidence: 99%

The Turbulence Characteristics of the Atmospheric Surface Layer on the North Slope of Mt. Everest Region in the Spring of 2005

Zhong

2012

Journal of the Meteorological Society of Japan

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Turbulence measurements at 3 m performed at the base camp of Mt. Everest during the spring of 2005 were used to study the atmospheric turbulent characteristics under conditions of down-slope ambient wind (katabatic wind). The cases where large-scale forcing resulted in a down-slope ambient wind were considered. Firstly, the normalized standard deviations of wind speed (u and v components) were larger than those reported in the literature. Then the (co)spectral characteristics of turbulence under near neutral stratification were described depending on the prevailing wind; case A-southerly with wind speed larger than 6 m s À1 during daytime, case B-southerly with wind speed less than 6 m s À1 and case C-northerly wind. The analysis of the averaged spectra and co-spectra revealed that low frequency perturbations had a large influence on the variance of u and w wind components, and also altered the co-spectra of momentum and sensible heat flux under near neutral stratification. The features of spectral shape and power were di¤erent from the previous ones under ideal flat and homogeneous conditions. The possible cause of these features is due to strong down-valley flow induced by (normal) glacier wind.

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“…covariance, wind direction, atmospheric stability, and all fluxes) by applying reasonable physical consistency limits. An overall quality classification strategy (Foken and Wichura, 1996;Foken et al, 2004) combining steady-state test and the integral turbulence characteristics test marked the derived 30-min fluxes with overall quality flags of 7-9 as low-quality data, and marked the flux data with flags of 1-6 as high-quality data for further analysis. The diagnostic signals (i.e.…”

Section: Generation Of High-quality Databasementioning

confidence: 99%

Improved data gap-filling schemes for estimation of net ecosystem exchange in typical East-Asian croplands

Zhao

Lüers

2016

Sci. China Earth Sci.

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The estimation of carbon exchange between ecosystems and the atmosphere suffers unavoidable data gaps in eddy-covariance technique, especially for short-living and fast-growing croplands. In this study we developed a modified gap-filling scheme introducing a leaf area index factor as the vegetation status information based on the conventional light response function for two East-Asian cropland sites (rice and potatoes). This scheme's performance is comparable to the conventional time window scheme, but has the advantage when the gaps are large compared to the total length of the time series. To investigate how the time binning approach performs for fast-growing croplands, we tested different widths of the time window, showing that a four-day window for the potato field and an eight-day time window for the rice field perform the best. The insufficiency of the conventional temperature binning approach was explained as well as the influence of vapor pressure deficit. We found that vapor pressure deficit plays a minor role in both the potato and the rice fields under Asian monsoon weather conditions with the exception of the early pre-monsoon growing stage of the potatoes. Consequently, we recommend using the conventional time-window scheme together with our new leaf-light response function to fill data gaps of net ecosystem exchange in fast-growing croplands.

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Tools for quality assessment of surface-based flux measurements

Cited by 1,474 publications

References 20 publications

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

The Turbulence Characteristics of the Atmospheric Surface Layer on the North Slope of Mt. Everest Region in the Spring of 2005

Improved data gap-filling schemes for estimation of net ecosystem exchange in typical East-Asian croplands

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