The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

Oncley, Steven; Foken, Thomas; Vogt, Roland; Kohsiek, W.; DeBruin, H.A.R.; Bernhofer, Christian; Christen, Andreas; Gorsel, Eva van; Grantz, David A.; Feigenwinter, Christian; Lehner, Irene; Liebethal, Claudia; Li, Heping; Mauder, Matthias; Pitacco, Andrea; Ribeiro, Luís Frölén; Weidinger, Tamás

doi:10.1007/s10546-007-9161-1

Cited by 336 publications

(308 citation statements)

References 49 publications

(46 reference statements)

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“…Note that the accuracy of J C relies on the quality of GPP data. Some of the energy fixed by photosynthesis is steadily released by respiration and is already accounted for in sensible heat storage change J H and heat storage change of biomass J veg (Blanken et al 1997;Oncley et al 2007). J C adds energy to the storage and should be therefore positive during day and is zero during periods without photosynthesis, i.e.…”

Section: Biochemical Heat Storage Change J Cmentioning

confidence: 99%

“…There are numerous studies reporting a lack of energy closure (e.g. Aubinet et al 2000;Barr et al 1994Barr et al , 2006Bernhofer 1992;Bernhofer and Vogt 1999;Blanford et al 1991;Blanken et al 1998;Finch and Harding 1998;Jarvis et al 1997;Kabat et al 1997;Laubach 1996;Malhi et al 2002;Oncley et al 2007;Twine et al 2000;Wilson et al 2002;Wilson and Baldocchi 2000). Wilson et al (2002) found an imbalance in the order of 20% for a number of FLUXNET sites.…”

Section: Introductionmentioning

confidence: 99%

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Available energy and energy balance closure at four coniferous forest sites across Europe

Moderow

Aubinet

Feigenwinter

et al. 2009

Theor Appl Climatol

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The available energy (AE), driving the turbulent fluxes of sensible heat and latent heat at the earth surface, was estimated at four partly complex coniferous forest sites across Europe (Tharandt, Germany; Ritten/Renon, Italy; Wetzstein, Germany; Norunda, Sweden). Existing data of net radiation were used as well as storage change rates calculated from temperature and humidity measurements to finally calculate the AE of all forest sites with uncertainty bounds. Data of the advection experiments MORE II (Tharandt) and ADVEX (Renon, Wetzstein, Norunda) served as the main basis. On-site data for referencing and cross-checking of the available energy were limited. Applied cross checks for net radiation (modelling, referencing to nearby stations and ratio of net radiation to global radiation) did not reveal relevant uncertainties. Heat storage of sensible heat J H , latent heat J E , heat storage of biomass J veg and heat storage due to photosynthesis J C were of minor importance during day but of some importance during night, where J veg turned out to be the most important one. Comparisons of calculated storage terms (J E , J H ) at different towers of one site showed good agreement indicating that storage change calculated at a single point is representative for the whole canopy at sites with moderate heterogeneity. The uncertainty in AE was assessed on the basis of literature values and the results of the applied cross checks for net radiation. The absolute mean uncertainty of AE was estimated to be between 41 and 52 W m −2 (10-11 W m −2 for the sum of the storage terms J and soil heat flux G) during mid-day (approximately 12% of AE). At night, the absolute mean uncertainty of AE varied from 20 to about 30 W m −2 (approximately 6 W m −2 for J plus G) resulting in large relative uncertainties as AE itself is small. An inspection of the energy balance showed an improvement of closure when storage terms were included and that the imbalance cannot be attributed to the uncertainties in AE alone.

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Section: Biochemical Heat Storage Change J Cmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Available energy and energy balance closure at four coniferous forest sites across Europe

Moderow

Aubinet

Feigenwinter

et al. 2009

Theor Appl Climatol

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“…In general, EBC ranges between 70 and 90 % as observed over different types of surface ranging from bare soil to a forest (Oncley et al, 2007;Wilson et al, 2002;Twine et al, 2000). 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).…”

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

confidence: 99%

“…Minor flux terms such as energy storage in the canopy or energy conversion by photosynthesis are generally neglected (see e.g., Leuning et al, 2012). However, several studies, where minor energy fluxes were carefully investigated as potential sources for the imbalance, show that considering these minor terms is relevant (Lamaud et al, 2001;Meyers and Hollinger, 2004;Oncley et al, 2007) and could even in some cases help to achieve a nearly perfect EBC (Jacobs et al, 2008). Usually the sum of the two turbulent fluxes measured with the EC method is systematically lower than the so-called available energy: the difference between net radiation (R n )…”

Section: Introductionmentioning

confidence: 99%

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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“…The software package TK3 (Mauder and Foken, 2011) post-processed high frequency (20 Hz) raw data to calculate 30-min aggregated fluxes of NEE and generate the observed database (Database-observation). This flux calculating and correcting strategy is well documented, intercompared by the international micrometeorology community (Mauder et al, 2008), and successfully applied during known major field experiments such as EBEX-2000 Oncley et al, 2007), LITFASS-2003, and COPS-2007 (Eigenmann et al, 2011). Automatic weather stations (AWS, WS-GP1, Delta-T Devices Ltd., UK) were used at both sites for the measurement of meteorological variables (5-min values), including air temperature, humidity, wind speed and direction, precipitation, and global radiation.…”

Section: Data Collectionmentioning

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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The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

Cited by 336 publications

References 49 publications

Available energy and energy balance closure at four coniferous forest sites across Europe

Available energy and energy balance closure at four coniferous forest sites across Europe

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

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

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