Corrections and Data Quality Control

Foken, Thomas; Leuning, R.; Oncley, S.; Mauder, Matthias; Aubinet, Marc

doi:10.1007/978-94-007-2351-1_4

Cited by 194 publications

(135 citation statements)

References 125 publications

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“…EC measurement was equipped with an ultrasonic anemometer (USA-1, METEK GmbH, Elmshorn, Germany) and a fast-response open-path infrared analyzer (LI-7500, LI-COR Inc., Lincoln, NE, USA), both working at a sampling frequency of 20 Hz at 2.5-m height above ground level in the potato field and 2.8-m height above the flooded water level in the rice field. The EC software package TK3 [21] post-processed the high-frequency raw data according to all international agreed procedures [22]. Half-hourly aggregated sensible and latent heat fluxes with quality flags [23] were available as results.…”

Section: Research Sites and Field Campaignsmentioning

confidence: 99%

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Zhao

Lüers

2017

Atmosphere

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Estimation of evapotranspiration plays an important role in understanding the water cycle on the earth, especially the water budget in agricultural ecosystems. The parameterization approach of the Penman-Monteith-Katerji-Perrier (PM-KP) model, accounting for the influence of meteorological variables and aerodynamic resistance on surface resistance, was proposed in the literature, but it has not been applied to Asian croplands, and its error and sensitivity have not been reported yet. In this study, the estimation of evapotranspiration on half-hourly scale was carried out for two typical East Asian cropland research sites, and evaluated by using eddy-covariance measurements corrected with the energy-balance-closure concept. Sensitivity coefficients as well as systematic bias and random errors of the PM-KP approach were used to evaluate the model performance. Different distributions of the calibration coefficients between different crops were reported for the first time, indicating that the calibration of this model was more stable for the rice field than for the potato field. The commonly-used parameterization approach suggested by the Food and Agriculture Organization (FAO) was used as reference and was site-specifically optimized. The results suggest that the PM-KP approach would be a better alternative than the PM-FAO approach for estimating evapotranspiration for the flooded rice field, and an acceptable alternative for rain-fed croplands when the soil is well watered and the air is humid during the summer monsoon.

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Section: Research Sites and Field Campaignsmentioning

confidence: 99%

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Zhao

Lüers

2017

Atmosphere

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“…Crosswind correction was used to account for a different type of sonic anemometer (Liu et al 2001), and a correction was used for the cross sensitivity between H 2 O and O 2 molecules (Tanner et al 1993), which was only applied for the Krypton hygrometer KH20 (deployed in A5 and A7). More details of these corrections can be found in and Foken et al (2012).…”

Section: Litfass-2003 Experiments and Data Processingmentioning

confidence: 99%

Extension of the Averaging Time in Eddy-Covariance Measurements and Its Effect on the Energy Balance Closure

Charuchittipan

Babel

Mauder

et al. 2014

Boundary-Layer Meteorol

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128

126

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The modified ogive analysis and the block ensemble average were employed to investigate the impact of the averaging time extension on the energy balance closure over six land-use types. The modified ogive analysis, which requires a steady-state condition, can extend the averaging time up to a few hours and suggests that an averaging time of 30 min is still overall sufficient for eddy-covariance measurements over low vegetation. The block ensemble average, which does not require a steady-state condition, can extend the averaging time to several days. However, it can improve the energy balance closure for some sites during specific periods, when secondary circulations exist in the vicinity of the sensor. These nearsurface secondary circulations mainly transport sensible heat, and when near-ground warm air is transported upward, the sensible heat flux observed by the block ensemble average will increase at longer averaging times. These findings suggest an alternative energy balance correction for a ground-based eddy-covariance measurement, in which the attribution of the residual depends on the ratio of sensible heat flux to the buoyancy flux. The fraction of the

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“…The air transportation through the long inlet tube (30 m) and the filters led to high-frequency loss in the signal (Foken et al, 2012a). To determine the damping factor, sufficient flux intervals with good conditions are needed, i.e., cases with a large significant flux and very stationary conditions resulting in a well-defined cospectrum and ogive with a low noise level.…”

Section: Flux Calculationmentioning

confidence: 99%

“…Moving sources in the FP lead to strong flux variations which are normally identified by the stationarity criterion (Foken et al, 2012a). We did not apply a stationarity test because it would have potentially removed cases with high cow contributions.…”

Section: Detection Limit and Flux Quality Selectionmentioning

confidence: 99%

Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

Felber

Münger²,

Neftel

et al. 2015

Biogeosciences

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Abstract. Methane (CH 4 ) from ruminants contributes onethird of global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH 4 analyzers, the instrumentation at many flux sites has been amended for these gases. However, the application of EC over pastures is challenging due to the spatially and temporally uneven distribution of CH 4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d −1 ) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to 2 orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH 4 head −1 d −1 (best estimate from this study) correspond well to animal respiration chamber measurements reported in the literature. However, a systematic effect of the distance between source and EC tower on cow emissions was found, which is attributed to the analytical footprint model used. We show that the EC method allows one to determine CH 4 emissions of cows on a pasture if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

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Corrections and Data Quality Control

Cited by 194 publications

References 125 publications

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Extension of the Averaging Time in Eddy-Covariance Measurements and Its Effect on the Energy Balance Closure

Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

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