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Journal ArticleDOI

Quality Control and Flux Sampling Problems for Tower and Aircraft Data

01 Jun 1997-Journal of Atmospheric and Oceanic Technology (American Meteorological Society)-Vol. 14, Iss: 3, pp 512-526
TL;DR: A series of automated tests is developed for tower and aircraft time series to identify instrumentation problems, flux sampling problems, and physically plausible but unusual situations and serves as a safety net for quality controlling data.
Abstract: A series of automated tests is developed for tower and aircraft time series to identify instrumentation problems, flux sampling problems, and physically plausible but unusual situations. The automated procedures serve as a safety net for quality controlling data. A number of special flags are developed representing a variety of potential problems such as inconsistencies between different tower levels and the flux error due to fluctuations of aircraft height. The tests are implemented by specifying critical values for parameters representing each specific error. The critical values are developed empirically from experience of applying the tests to real turbulent time series. When these values are exceeded, the record is flagged for further inspection and comparison with the rest of the concurrent data. The inspection step is necessary to either verify an instrumentation problem or identify physically plausible behavior. The set of tests is applied to tower data from the Riso Air Sea Experiment and...

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Citations
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Book ChapterDOI
TL;DR: In this article, the authors have described the measurement system and the procedure followed for the computation of the fluxes and procedure of flux summation, including data gap filling strategy, night flux corrections and error estimation.
Abstract: Publisher Summary The chapter has described the measurement system and the procedure followed for the computation of the fluxes and the procedure of flux summation, including data gap filling strategy, night flux corrections and error estimation. It begins with the introduction of estimates of the annual net carbon and water exchange of forests using the EUROFLUX methodology. The chapter then provides us with the theory and moves on to discuss the eddy covariance system and its sonic anemometer, temperature fluctuation measurements, infrared gas analyser, air transport system, and tower instrumentation. Additional measurements are also given in the chapter. Data acquisition and its computation and correction is discussed next in the chapter by giving its general procedure, half-hourly means (co-)variances and uncorrected fluxes, intercomparison of software, and correction for frequency response losses. The chapter has also discussed about quality control and four criteria are investigated here for the same. Spatial representativeness of measured fluxes and summation procedure are reviewed. The chapter then moves on to the discussion of data gap filling through interpolation and parameterization and neural networks. Corrections to night-time data and error estimation are also explored in the chapter. Finally, the chapter closes with conclusions.

1,870 citations

Journal ArticleDOI
TL;DR: It will be shown that former assumptions that measuring errors or storage terms are the reason for the unclosed energy balance do not stand up because even turbulent fluxes derived from documented methods and calibrated sensors, net radiation, and ground heat fluxes cannot close the energy balance.
Abstract: This paper gives an overview of 20 years of research on the energy balance closure problem. It will be shown that former assumptions that measuring errors or storage terms are the reason for the unclosed energy balance do not stand up because even turbulent fluxes derived from documented methods and calibrated sensors, net radiation, and ground heat fluxes cannot close the energy balance. Instead, exchange processes on larger scales of the heterogeneous landscape have a significant influence. By including these fluxes, the energy balance can be approximately closed. Therefore, the problem is a scale problem and has important consequences to the measurement and modeling of turbulent fluxes.

1,150 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a two-part series of recommendations for documentation to be associated with published evapotranspiration (ET) data and provide guidelines for reducing error in ET retrievals.

743 citations


Cites methods from "Quality Control and Flux Sampling P..."

  • ...A variety of software programs for correction of EC data have been produced, including ECPack from Wageningen University, TK2 software of the University of Bayreuth (Mauder and Foken, 2004), EddySoft developed at the Max-Planck-Institute for Biogeochemistry in Jena (Kolle and Rebmann, 2007), EdiRE software from the University of Edin- burgh, and APAK by Oregon State University (Vickers and Mahrt, 1997, 2003)....

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  • ...…TK2 software of the University of Bayreuth (Mauder and Foken, 2004), EddySoft developed at the Max-Planck-Institute for Biogeochemistry in Jena (Kolle and Rebmann, 2007), EdiRE software from the University of Edin- burgh, and APAK by Oregon State University (Vickers and Mahrt, 1997, 2003)....

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Book ChapterDOI
01 Jan 2004
TL;DR: In this article, the authors summarized the steps of quality assurance and quality control of flux measurements with the eddy covariance method and the fulfillment of the theoretical assumptions of the measuring method and thenonsteady state test and the integral turbulence test.
Abstract: This Chapter summarizes the steps of quality assurance and quality control of flux measurements with the eddy covariance method An important part is the di erent steps of the control for electronic, meteorological and statistical problems The fulfillment of the theoretical assumptions of the measuring method and thenon-steady state test and the integral turbulence test are extensively discussed as well as an overall flagging for data quality and a site specific quality analysis using footprint models Finally, problems are discussed which are not included yet in the control program, mainly connected with the complicated turbulence structure at a forest site

640 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured CO2 efflux with chambers periodically in 1996-97 in a ponderosa pine forest in Oregon, scaled these measurements to the ecosystem, and computed annual totals for respiration by component.
Abstract: The net ecosystem exchange of CO2 between forests and the atmosphere, measured by eddy covariance, is the small difference between two large fluxes of photosynthesis and respiration Chamber measurements of soil surface CO2 efflux (Fs), wood respiration (Fw) and foliage respiration (Ff) help identify the contributions of these individual components to net ecosystem exchange Models developed from the chamber data also provide independent estimates of respiration costs We measured CO2 efflux with chambers periodically in 1996–97 in a ponderosa pine forest in Oregon, scaled these measurements to the ecosystem, and computed annual totals for respiration by component We also compared estimated half-hourly ecosystem respiration at night (Fnc) with eddy covariance measurements Mean foliage respiration normalized to 10 °C was 020 μmol m–2 (hemi-leaf surface area) s–1, and reached a maximum of 024 μmol m–2 HSA s–1 between days 162 and 208 Mean wood respiration normalized to 10 °C was 59 μmol m–3 sapwood s–1, with slightly higher rates in mid-summer, when growth occurs There was no significant difference (P > 010) between wood respiration of young (45 years) and old trees (250 years) Soil surface respiration normalized to 10 °C ranged from 07 to 30 μmol m–2 (ground) s–1 from days 23 to 329, with the lowest rates in winter and highest rates in late spring Annual CO2 flux from soil surface, foliage and wood was 683, 157, and 54 g C m–2 y–1, with soil fluxes responsible for 76% of ecosystem respiration The ratio of net primary production to gross primary production was 045, consistent with values for conifer sites in Oregon and Australia, but higher than values reported for boreal coniferous forests Below-ground carbon allocation (root turnover and respiration, estimated as Fs– litterfall carbon) consumed 61% of GPP; high ratios such as this are typical of sites with more water and nutrient constraints The chamber estimates were moderately correlated with change in CO2 storage in the canopy (Fstor) on calm nights (friction velocity u* 025 m s–1), the sum of turbulent flux measured above the canopy by eddy covariance and Fstor was only weakly correlated with summed chamber estimates (R2 = 014); the eddy covariance estimates were lower than chamber estimates by 50%

492 citations


Cites background from "Quality Control and Flux Sampling P..."

  • ...Non-stationarity (e.g. wind speed increasing during the averaging window) generally occurs with weak large-scale flow and mesoscale variability, and is more frequent over heterogeneous terrain (Vickers & Mahrt 1997)....

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References
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Journal ArticleDOI
TL;DR: In this article, the free constants in several interpolation formulas can be adjusted to give excellent fits to the wind and temperature gradient data, and the behavior of the gradients under neutral conditions is unusual, however, and indicates that von Karman's constant is ∼0.35, rather than 0.40 as usually assumed, and that the ratio of eddy diffusivities for heat and momentum at neutrality is ∼1.0.
Abstract: Wind and temperature profiles for a wide range of stability conditions have been analyzed in the context of Monin-Obukhov similarity theory. Direct measurements of heat and momentum fluxes enabled determination of the Obukhov length L, a key independent variable in the steady-state, horizontally homogeneous, atmospheric surface layer. The free constants in several interpolation formulas can be adjusted to give excellent fits to the wind and temperature gradient data. The behavior of the gradients under neutral conditions is unusual, however, and indicates that von Karman's constant is ∼0.35, rather than 0.40 as usually assumed, and that the ratio of eddy diffusivities for heat and momentum at neutrality is ∼1.35, compared to the often-suggested value of 1.0. The gradient Richardson number, computed from the profiles, and the Obukhov stability parameter z/L, computed from the measured fluxes, are found to be related approximately linearly under unstable conditions. For stable conditions the Richar...

3,177 citations


"Quality Control and Flux Sampling P..." refers background or methods in this paper

  • ...We calculate vertical gradients of wind speed, potential temperature, and specific humidity using the fluxprofile relationships of Monin–Obukhov similarity theory (Businger et al. 1971; Dyer 1974) and the observed fluxes....

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  • ...ory (Businger et al. 1971; Dyer 1974) and the observed...

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Journal ArticleDOI
TL;DR: In this paper, Businger et al. reviewed the preferred relationships of Dyer and Hicks (1970) in the constant flux layer, and found that the preferred relationship was the one of the Dyer-H Hicks pair.
Abstract: Flux-profile relationships in the constant flux layer are reviewed The preferred relationships are found to be those of Dyer and Hicks (1970), namely, φ H =φ W =(1−16(z/L))−1/2, φ M =(1−16(z/L))−1/4 for the unstable region, and φ H =φ W =φ M = 1+5(z/L) for the stable region The carefully determined results of Businger et al (1971) remain a difficulty which calls for considerable clarification

1,564 citations


"Quality Control and Flux Sampling P..." refers methods in this paper

  • ...We calculate vertical gradients of wind speed, potential temperature, and specific humidity using the fluxprofile relationships of Monin–Obukhov similarity theory (Businger et al. 1971; Dyer 1974) and the observed fluxes....

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Journal ArticleDOI
TL;DR: A scheme for the characterization of the quality of direct turbulence measurements using the Navier-Stokes equations, which are the basis of direct surface-based measurements of turbulent fluxes via the eddy correlation method.

1,456 citations


"Quality Control and Flux Sampling P..." refers background in this paper

  • ...Foken and Wichura (1996) apply criteria to fast-response turbulence data to test for nonstationarity and substantial deviations from flux-variance similarity theory, whether instrumental or physical....

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  • ...Foken and Wichura (1996) apply criteria to fast-response turbulence data to test for nonstationarity and substantial deviations from flux-variance similarity theory, whether instrumental or physical....

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Journal ArticleDOI
TL;DR: The Boreal Ecosystem Atmosphere Study (BOREAS) as mentioned in this paper is a large-scale international field experiment that has the goal of improving our understanding of the exchanges of radiative energy, heat water, CO2, and trace gases between the boreal forest and the lower atmosphere.
Abstract: The Boreal Ecosystem Atmosphere Study (BOREAS) is large-scale international field experiment that has the goal of improving our understanding of the exchanges of radiative energy, heat water, CO2, and trace gases between the boreal forest and the lower atmosphere. An important objective of BORES is collect the data needed to improve computer simulation models of the processes controlling these exchanges so that scientists can anticipate the effects of global change. From August 1993 through September 1994, a continuous set of monitoring measurements—meteorology, hydrology, and satellite remote sensing—were gathered over the 1000 × 1000 km BOREAS study region that covers most of Saskatchewan and Manitoba, Canada. This monitoring program was punctuated by six campaigns that saw the deployment of some 300 scientists and aircrew into the field, supported by 11 research aircraft. The participants were drawn primarily from U.S. and Canadian agencies and universities, although there were also important ...

658 citations

Journal ArticleDOI
TL;DR: A statistical method for automatic quality control of measurement data with distributions close to Gaussian is presented and, using the best one of these, the method is tested using artificial and real turbulence data.
Abstract: A statistical method for automatic quality control of measurement data with distributions close to Gaussian is presented. For each data point a prediction is made, based on the mean, variance and point-to-point correlation of the time series. The predicted value is compared with the actual value and if the difference between the two is 'large' then that data point is either marked as an outlier or replaced by the forecast value. Four different prediction methods are tested and, using the best one of these, the method is tested using artificial and real turbulence data.

164 citations


"Quality Control and Flux Sampling P..." refers methods or result in this paper

  • ...In Højstrup (1993), a data screening procedure for application to Gaussian distributed turbulence data is tested....

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  • ...The spike detection and removal method is similar to that of Højstrup (1993). The method computes the mean and standard deviation for a series of moving windows of length L1....

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  • ...The spike detection and removal method is similar to that of Højstrup (1993)....

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