Towards Closing the Surface Energy Budget of a Mid-latitude Grassland

Jacobs, A.F.G.; Heusinkveld, B.G.; Holtslag, A.A.M.

doi:10.1007/s10546-007-9209-2

Cited by 90 publications

(89 citation statements)

References 29 publications

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“…In most cases, data on energy storage components were unavailable, and energy balance closure was not achieved (Wilson et al 2002;Jacobs et al 2008). In these instances, a bulk storage term dG/dt was estimated from the hourly energy balance residual, and its associated entropy change was calculated by dividing dG by the ambient air temperature.…”

Section: (D) Entropy Of Sensible and Latent Heat Flowsmentioning

confidence: 99%

Trends in entropy production during ecosystem development in the Amazon Basin

Holdaway

Sparrow

Coomes

2010

Phil. Trans. R. Soc. B

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Understanding successional trends in energy and matter exchange across the ecosystematmosphere boundary layer is an essential focus in ecological research; however, a general theory describing the observed pattern remains elusive. This paper examines whether the principle of maximum entropy production could provide the solution. A general framework is developed for calculating entropy production using data from terrestrial eddy covariance and micrometeorological studies. We apply this framework to data from eight tropical forest and pasture flux sites in the Amazon Basin and show that forest sites had consistently higher entropy production rates than pasture sites (0.461 versus 0.422 W m 22 K 21 , respectively). It is suggested that during development, changes in canopy structure minimize surface albedo, and development of deeper root systems optimizes access to soil water and thus potential transpiration, resulting in lower surface temperatures and increased entropy production. We discuss our results in the context of a theoretical model of entropy production versus ecosystem developmental stage. We conclude that, although further work is required, entropy production could potentially provide a much-needed theoretical basis for understanding the effects of deforestation and land-use change on the land-surface energy balance.

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Section: (D) Entropy Of Sensible and Latent Heat Flowsmentioning

confidence: 99%

Trends in entropy production during ecosystem development in the Amazon Basin

Holdaway

Sparrow

Coomes

2010

Phil. Trans. R. Soc. B

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“…Accounting for these fluxes would probably help to improve the EBC at our study site. Jacobs et al (2008), for example, showed that EBC could be improved at a grassland site by 15 % by elaborate estimation of ground heat flux (9 %) and considering energy consumption by photosynthesis and other minor storage terms such as enthalpy storage in the air layer between turbulent complex and the land surface (6 %). Meyers and Hollinger (2004) demonstrated that combining soil heat storage with canopy heat and photosynthetic energy flux improved the EBC by 15 and 7 % for a fully developed maize and soybean site, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…A small fraction of the energy balance gap may also be explained by energy storage in the canopy and photosynthetic energy flux. Both components are normally neglected due to their alleged small contribution (Foken, 2008a;Guo et al, 2009;Jacobs et al, 2008).…”

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%

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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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“…For an irrigated cotton field, Oncley et al (2007) computed for the energy consumption by photosynthesis a diurnal average value of 8 W m −2 with a half-hourly peak value of formidable 48 W m −2 . Jacobs et al (2008) calculated in their study all possible enthalpy changes, such as the soil heat storage, vegetation cover heat storage, dew water heat storage, air mass heat storage, and the photosynthesis energy flux for a grass land site. By doing so, they were able improve the EBR of the EC flux data from 84 to 96 %.…”

Section: Energy Balance Closure (%)mentioning

confidence: 99%

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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Towards Closing the Surface Energy Budget of a Mid-latitude Grassland

Cited by 90 publications

References 29 publications

Trends in entropy production during ecosystem development in the Amazon Basin

Trends in entropy production during ecosystem development in the Amazon Basin

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

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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