Surface energy balance closure in an arid region: role of soil heat flux

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

doi:10.1016/j.agrformet.2003.09.005

Cited by 247 publications

(203 citation statements)

References 15 publications

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“…He concluded that the observed lack of EBC on the local scale in heterogeneous landscape can be explained only by deficits in measurement concepts and methodologies. This conclusion is supported by Heusinkveld et al (2004); they found a perfect EBC over a homogeneous surface: a desert in Israel. Tsvang et al (1991) and Stoy et al (2013) also concluded that the heterogeneities of the surrounding area are an important factor contributing to the lack of EBC.…”

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

confidence: 73%

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

confidence: 73%

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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“…Smaller imbalances were found in homogenous terrain with little deviation from the 'ideal site requirement' (e.g. Grelle and Lindroth 1996;Heusinkveld et al 2004;Mauder et al 2007a).…”

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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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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“…In the present data set, under the constraints of the common surface energy balance, it appears that soil heat flux measurement depth should exceed 3-cm below the soil surface; measurements as deep as 6-cm are necessary to provide some confidence that the evaporation zone is fully above the measurement depth for the 10-day rain-free period. In situations where the latent heat flux term is negligible and/or soil water storage and evaporation are minimal, shallower measurement depths may be possible (e.g., Heusinkveld et al, 2004). Extrapolation or interpolation of heat flux observations between depths should also be performed cautiously by explicitly accounting for the location and strength of the latent heat flux.…”

Section: Latent Heat Sinkmentioning

confidence: 99%

“…Sauer and Horton (2005) reviewed a variety of techniques that have come to be considered de facto standards for determining soil heat flux, including heat flux plates and the combination method. Yet, there remains uncertainty about what comprises soil heat flux and how surface and subsurface heat flux are linked in energy balance closure (Passerat de Silans et al, 1997;Heusinkveld et al, 2004;Holmes et al, 2008;Wang and Bras, 2009;Holmes et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Ochsner et al (2007) suggested that, when neglecting the heat storage term, soil heat flux measured at the 6-cm soil depth might underestimate surface heat flux by more than 50%. Owing to concerns with the link between surface and subsurface heat flux, Heusinkveld et al (2004) suggested "burying the sensor as close to the surface as possible" in dry, bare soil with a very high surface heat flux. However, the presence of a drying front may limit such an installation approach in conditions where subsurface soil moisture, and hence latent heat of vaporization of soil water, is important (Sauer and Horton, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Latent heat in soil heat flux measurements

Heitman

Horton

Sauer

et al. 2010

Agricultural and Forest Meteorology

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The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, there remains uncertainty about what comprises soil heat flux and how surface and subsurface heat fluxes are linked in energy balance closure. The objective of this study is to demonstrate the presence of a subsurface latent heat sink, which must be considered in order to accurately link subsurface heat fluxes between depths near and at the soil surface. Measurements were performed under effectively bare surface conditions in a silty clay loam soil near Ames, IA. Soil heat flux was measured with heat-pulse sensors using the gradient heat flux approach at 1-, 3-, and 6-cm soil depths. Independent estimates of the daily latent heat sink were obtained by measuring the change of mass of microlysimeters. Heat flux measurements at the 1-cm depth deviated from heat flux measurements at other depths, even after calorimetric adjustment was made. This deviation was most pronounced shortly after rainfall, where the 1-cm soil heat flux measurement exceeded 400 W m−2. Cumulative soil heat flux measurements at the 1-cm depth exceeded measurements at the 3-cm depth by >75% over a 7-day rain-free period, whereas calorimetric adjustment allowed 3-and 6-cm depth measurements to converge. Latent heat sink estimates from the microlysimeters accounted for nearly all of the differences between the 1-and 3-cm depth heat flux measurements, indicating that the latent heat sink was distributed between the 1-and 3-cm depths shortly after the rainfall event. Results demonstrate the importance of including latent heat when attempts are made to link or extrapolate subsurface soil heat flux measurements to the surface soil heat flux. The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, there remains uncertainty about what comprises soil heat flux and how surface and subsurface heat fluxes are linked in energy balance closure. The objective of this study is to demonstrate the presence of a subsurface latent heat sink, which must be considered in order to accurately link subsurface heat fluxes between depths near and at the soil surface. Measurements were performed under effectively bare surface conditions in a silty clay loam soil near Ames, IA. Soil heat flux was measured with heat-pulse sensors using the gradient heat flux approach at 1-, 3-, and 6-cm soil depths. Independent estimates of the daily latent heat sink were obtained by measuring the change of mass of microlysimeters. Heat flux measurements at the 1-cm depth deviated from heat flux measurements at other depths, even after calorimetric adjust...

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Surface energy balance closure in an arid region: role of soil heat flux

Cited by 247 publications

References 15 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

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

Latent heat in soil heat flux measurements

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