Sensitivity analysis for two ground heat flux calculation approaches

Liebethal, Claudia; Huwe, Bernd; Foken, Thomas

doi:10.1016/j.agrformet.2005.08.001

Cited by 158 publications

(107 citation statements)

References 18 publications

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“…1 were measured at each station. Details of these measurements were well described in and Liebethal et al (2005). These measurements allow estimation of the residual, which, on average, reached its maximum at 1000-1200 Table 1).…”

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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124

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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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

Self Cite

124

126

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“…When applying the maximum measurement errors assumed by Liebethal et al (2005) for the LITFASS-2003 data sets, the error of the resulting ground heat flux at the surface is smaller than 15 W m −2 for most of the 30 min data. Based on the above results, we are convinced that measurement errors or uncertainties in the determination of the net radiation, the ground heat flux and the turbulent fluxes are not the reason for the energy imbalance in our data sets.…”

Section: Net Radiation and Ground Heat Fluxmentioning

confidence: 99%

“…To determine the ground heat flux, all sites were equipped with additional soil sensors. According to the sensitivity analysis by Liebethal et al (2005), the most reliable way to determine the ground heat flux turned out to be a combination of two methods, namely the gradient approach and the calorimetry. The soil heat flux at a socalled reference depth of about 0.20 m is determined from the vertical soil temperature gradient and soil thermal conductivity at that depth according to Fourier's law of heat conduction.…”

Section: Net Radiation and Ground Heat Fluxmentioning

confidence: 99%

Energy balance closure for the LITFASS-2003 experiment

Foken

Mauder

Liebethal

et al. 2009

Theor Appl Climatol

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140

108

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In the first part, this paper synthesises the main results from a series of previous studies on the closure of the local energy balance at low-vegetation sites during the LITFASS-2003 experiment. A residual of up to 25% of the available energy has been found which cannot be fully explained either by the measurement uncertainty of the single components of the surface energy balance or by the length of the flux-averaging period. In the second part, secondary circulations due to heterogeneities in the surface characteristics (roughness, thermal and moisture properties) are discussed as a possible cause for the observed energy balance non-closure. This hypothesis seems to be supported from the fluxes derived from area-averaging measurement techniques (scintillometers, aircraft).

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“…where R n is net radiation (W m À2 ), H is sensible heat flux (W m À2 ), and G is ground heat flux (W m À2 ) calculated following Liebethal et al [2005]. To compute the total seasonal deficit in the energy budget, daily deficits were summed over the duration of the season.…”

Section: Eddy Covariance Measurementsmentioning

confidence: 99%

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

et al. 2014

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Intermediate disturbances shape forest structure and composition, which may in turn alter carbon, nitrogen, and water cycling. We used a large-scale experiment in a forest in northern lower Michigan where we prescribed an intermediate disturbance by stem girdling all canopy-dominant early successional trees to simulate an accelerated age-related senescence associated with natural succession. Using 3 years of eddy covariance and sap flux measurements in the disturbed area and an adjacent control plot, we analyzed disturbance-induced changes to plot level and species-specific transpiration and stomatal conductance. We found transpiration to be~15% lower in disturbed plots than in unmanipulated control plots. However, species-specific responses to changes in microclimate varied. While red oak and white pine showed increases in stomatal conductance during postdisturbance (62.5 and 132.2%, respectively), red maple reduced stomatal conductance by 36.8%. We used the hysteresis between sap flux and vapor pressure deficit to quantify diurnal hydraulic stress incurred by each species in both plots. Red oak, a ring porous anisohydric species, demonstrated the largest mean relative hysteresis, while red maple, bigtooth aspen, and paper birch, all diffuse porous species, had the lowest relative hysteresis. We employed the Penman-Monteith model for LE to demonstrate that these species-specific responses to disturbance are not well captured using current modeling strategies and that accounting for changes to leaf area index and plot microclimate are insufficient to fully describe the effects of disturbance on transpiration.

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Sensitivity analysis for two ground heat flux calculation approaches

Cited by 158 publications

References 18 publications

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

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

Energy balance closure for the LITFASS-2003 experiment

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

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