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

Charuchittipan, Doojdao; Babel, Wolfgang; Mauder, Matthias; Leps, Jens-Peter; Foken, Thomas

doi:10.1007/s10546-014-9922-6

Cited by 123 publications

(138 citation statements)

References 51 publications

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“…The EBCs of the present study agree with those of other studies performed over agricultural land, where EBCs are typically characterized by high energy residuals (20-40%) (Charuchittipan et al, 2014;Foken, 2008a;Panin and Bernhofer, 2008;Stoy et al, 2013). The random errors of our EC fluxes are also in a good agreement with random errors reported by Mauder et al (2013) and Foken (2008a).…”

Section: Discussionsupporting

confidence: 92%

“…Low EBCs (60-80 %) were mainly observed at various agricultural sites and bare soil, whereas over forest they were typically higher (80-90 %) (Charuchittipan et al, 2014;Wilson et al, 2002;Foken, 2008a;Panin and Bernhofer, 2008;Stoy et al, 2013). The imbalance usually occurs during day time, particularly around noon, whereas during the night when fluxes are low EBC is often close to unity (Oncley et al, 2007).…”

Section: K Imukova Et Al: Energy Balance Closure On a Winter Wheat mentioning

confidence: 96%

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Energy balance closure on a winter wheat stand: comparing the eddy covariance technique with the soil water balance method

et al. 2016

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Abstract. The energy balance of eddy covariance (EC) flux data is typically not closed. The nature of the gap is usually not known, which hampers using EC data to parameterize and test models. In the present study we crosschecked the evapotranspiration data obtained with the EC method (ET EC ) against ET rates measured with the soil water balance method (ET WB ) at winter wheat stands in southwest Germany. During the growing seasons 2012 and 2013, we continuously measured, in a half-hourly resolution, latent heat (LE) and sensible (H ) heat fluxes using the EC technique. Measured fluxes were adjusted with either the Bowen-ratio (BR), H or LE post-closure method. ET WB was estimated based on rainfall, seepage and soil water storage measurements. The soil water storage term was determined at sixteen locations within the footprint of an EC station, by measuring the soil water content down to a soil depth of 1.5 m. In the second year, the volumetric soil water content was additionally continuously measured in 15 min resolution in 10 cm intervals down to 90 cm depth with sixteen capacitance soil moisture sensors. During the 2012 growing season, the H post-closed LE flux data (ET EC = 3.4 ± 0.6 mm day −1 ) corresponded closest with the result of the WB method (3.3 ± 0.3 mm day −1 ). ET EC adjusted by the BR (4.1 ± 0.6 mm day −1 ) or LE (4.9 ± 0.9 mm day −1 ) post-closure method were higher than the ET WB by 24 and 48 %, respectively. In 2013, ET WB was in best agreement with ET EC adjusted with the H postclosure method during the periods with low amount of rain and seepage. During these periods the BR and LE postclosure methods overestimated ET by about 46 and 70 %, respectively. During a period with high and frequent rainfalls, ET WB was in-between ET EC adjusted by H and BR post-closure methods. We conclude that, at most observation periods on our site, LE is not a major component of the energy balance gap. Our results indicate that the energy balance gap is made up by other energy fluxes and unconsidered or biased energy storage terms.

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Section: Discussionsupporting

confidence: 92%

Section: K Imukova Et Al: Energy Balance Closure On a Winter Wheat mentioning

confidence: 96%

Energy balance closure on a winter wheat stand: comparing the eddy covariance technique with the soil water balance method

et al. 2016

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“…The imbalance in Equation (1), often found when Q H and Q E are obtained from the measurement by the EC technique [31][32][33], can be significantly compensated with the contribution from secondary circulations which can hardly be measured by the EC system [31,34]. This study followed the energy balance closure (EBC) correction suggested by Charuchittipan et al [34]: where Res is the residue energy flux, c p is the specific heat of air, λ is the heat of evaporation for water, and superscripts indicate the measurement or correction methods. Bo EBC-HB is the corrected Bowen ratio, which should be either calculated iteratively until it converges [34] or calculated by solving Equation (2), which results in the analytic solution:…”

Section: Correction For Energy Balance Closurementioning

confidence: 99%

“…This study followed the energy balance closure (EBC) correction suggested by Charuchittipan et al [34]: where Res is the residue energy flux, c p is the specific heat of air, λ is the heat of evaporation for water, and superscripts indicate the measurement or correction methods. Bo EBC-HB is the corrected Bowen ratio, which should be either calculated iteratively until it converges [34] or calculated by solving Equation (2), which results in the analytic solution:…”

Section: Correction For Energy Balance Closurementioning

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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“…The authors argue that stationarity can be still assumed, because for the investigated 16-day time series the diurnal cycle was similar each day, and the trend of adjacent averages, which is the crucial stationarity criterion for the EC method, was smaller for 24 h values than for 30 min values. The finding that at some sites the energy residual may consist to a large extent of sensible heat was recently supported by an in-depth evaluation of additional EC flux data of the LITFASS-2003 experiment acquired over six different land use types (Charuchittipan et al, 2014).…”

Section: Introductionmentioning

confidence: 84%

On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

et al. 2015

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Abstract. The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modelling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure methods uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux (H ) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in southwest Germany in 2011, and the performance of the Jarvis and Ball-Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W m −2 (21 % of net radiation). Our study shows that it is crucial to account for the uncertainty in EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model-data comparisons.

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

Cited by 123 publications

References 51 publications

Energy balance closure on a winter wheat stand: comparing the eddy covariance technique with the soil water balance method

Energy balance closure on a winter wheat stand: comparing the eddy covariance technique with the soil water balance method

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

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