Structure of Carbon Dioxide Exchange Processes Above a Spruce Forest

Wichura, Bodo; Ruppert, Johannes; Delany, A. C.; Buchmann, Nina; Foken, Thomas

doi:10.1007/978-3-662-06073-5_9

Cited by 12 publications

(6 citation statements)

References 17 publications

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“…It is located in the transition zone from maritime to continental climates with annual average temperatures of 5.0 • C (1971Foken, 2003) and average annual precipitation sum of 1162 mm (1971Foken, 2003). The study site has been maintained for more than 10 years by the University of Bayreuth and a variety of studies have been conducted there (Falge et al, 2005;Held and Klemm, 2006;Klemm et al, 2006;Rebmann et al, 2005;Thomas and Foken, 2007;Wichura et al, 2004). The stand age of the Norway spruce (Picea abies) was approx.…”

Section: Spruce Forest Site Germany (Eger)mentioning

confidence: 99%

Aerodynamic gradient measurements of the NH3-HNO3-NH4NO3 triad using a wet chemical instrument: an analysis of precision requirements and flux errors

et al. 2010

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Abstract. The aerodynamic gradient method is widely used for flux measurements of ammonia, nitric acid, particulate ammonium nitrate (the NH 3 -HNO 3 -NH 4 NO 3 triad) and other water-soluble reactive trace compounds. The surface exchange flux is derived from a measured concentration difference and micrometeorological quantities (turbulent exchange coefficient). The significance of the measured concentration difference is crucial for the significant determination of surface exchange fluxes. Additionally, measurements of surface exchange fluxes of ammonia, nitric acid and ammonium nitrate are often strongly affected by phase changes between gaseous and particulate compounds of the triad, which make measurements of the four individual species (NH 3 , HNO 3 , NH + 4 , NO − 3 ) necessary for a correct interpretation of the measured concentration differences.We present here a rigorous analysis of results obtained with a multi-component, wet-chemical instrument, able to simultaneously measure gradients of both gaseous and particulate trace substances. Basis for our analysis are two field experiments, conducted above contrasting ecosystems (grassland, forest). Precision requirements of the instrument as well as errors of concentration differences and micrometeorological exchange parameters have been estimated, which, in turn, allows the establishment of thorough error estimates of the derived fluxes of NH 3 , HNO 3 , NH + 4 , and NO − 3 . Derived median flux errors for the grassland and forest field experiments were: 39% and 50% (NH 3 ), 31% and 38% (HNO 3 ), 62% and 57% (NH + 4 ), and 47% and 68% (NO − 3 ), respectively. Additionally, we provide the basis for using Correspondence to: V. Wolff (veronika.wolff@art.admin.ch) field data to characterize the instrument performance, as well as subsequent quantification of surface exchange fluxes and underlying mechanistic processes under realistic ambient measurement conditions.

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Section: Spruce Forest Site Germany (Eger)mentioning

confidence: 99%

Aerodynamic gradient measurements of the NH3-HNO3-NH4NO3 triad using a wet chemical instrument: an analysis of precision requirements and flux errors

et al. 2010

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“…In addition to the high-frequency observations a vertical array of cup anemometers was deployed on the same tower to measure the mean horizontal wind profile. Preliminary investigations were done by Wichura et al (2004) analysing a single day of measurements in summer 2000 at the same site. The present study expands previous ones, and includes: (i) a large dataset with up to approximately 3300 individual 30-min intervals analysed using a consistent, automated treatment based on the wavelet transform and Fourier transform, (ii) a variety of observed variables such as horizontal and vertical wind components, sonic temperature and carbon dioxide concentrations at several observation heights within and above the canopy; (iii) a large range of atmospheric stabilities, and (iv) upstream surface conditions varying with wind direction allowing one to study their effects on the organised turbulent motion.…”

Section: Introductionmentioning

confidence: 99%

Organised Motion in a Tall Spruce Canopy: Temporal Scales, Structure Spacing and Terrain Effects

Thomas

Foken

2006

Boundary-Layer Meteorol

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This study investigates the organised motion near the canopy-atmosphere interface of a moderately dense spruce forest in heterogeneous, complex terrain. Wind direction is used to assess differences in topography and surface properties. Observations were obtained at several heights above and within the canopy using sonic anemometers and fast-response gas analysers over the course of several weeks. Analysed variables include the three-dimensional wind vector, the sonic temperature, and the concentration of carbon dioxide. Wavelet analysis was used to extract the organised motion from time series and to derive its temporal scales. Spectral Fourier analysis was deployed to compute power spectra and phase spectra. Profiles of temporal scales of ramp-like coherent structures in the vertical and longitudinal wind components showed a reversed variation with height and were of similar size within the canopy. Temporal scales of scalar fields were comparable to those of the longitudinal wind component suggesting that the lateral scalar transport dominates. The existence of a -1 power law in the longitudinal power spectra was confirmed for a few cases only, with a majority showing a clear 5/3 decay. The variation of effective scales of organised motion in the longitudinal velocity and temperature were found to vary with atmospheric stability, suggesting that both Kelvin-Helmholtz instabilities and attached eddies dominate the flow with increasing convectional forcing. The canopy mixing-layer analogy was observed to be applicable for ramp-like coherent structures in the vertical wind component for selected wind directions only. Departures from the prediction of m = w L −1 s = 8-10 (where w is the streamwise spacing of coherent structures in the vertical wind w and L s is a canopy shear length scale) were caused by smaller shear length scales associated with large-scale changes in the terrain as well as the vertical structure of the canopy. The occurrence of linear gravity 124 Boundary-Layer Meteorol (2007) 122:123-147 waves was related to a rise in local topography and can therefore be referred to as mountain-type gravity waves. Temporal scales of wave motion and ramp-like coherent structures were observed to be comparable.

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“…The general high quality of carbon dioxide fluxes may also result from the fact that the turbulence structures are different for scalars compared to the wind components (Katul et al, 1996; Wichura et al, 2002). High frequency structures are not present and thus quality tests should be refined.…”

Section: Latent Heat Flux Ementioning

confidence: 99%

Quality analysis applied on eddy covariance measurements at complex forest sites using footprint modelling

Rebmann

Göckede

Foken

et al. 2004

Theor. Appl. Climatol.

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187

120

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SummaryMeasuring turbulent fluxes with the eddy covariance method has become a widely accepted and powerful tool for the determination of long term data sets for the exchange of momentum, sensible and latent heat, and trace gases such as CO 2 between the atmosphere and the underlying surface. Several flux networks developed continuous measurements above complex terrain, e.g. AmeriFlux and EUROFLUX, with a strong focus on the net exchange of CO 2 between the atmosphere and the underlying surface. Under many conditions basic assumptions for the eddy covariance method in its simplified form, such as stationarity of the flow, homogeneity of the surface and fully developed turbulence of the flow field, are not fulfilled. To deal with non-ideal conditions which are common at many FLUXNET sites, quality tests have been developed to check if these basic theoretical assumptions are valid.In the framework of the CARBOEUROFLUX project, we combined quality tests described by Foken and Wichura (1996) with the analytical footprint model of Schmid (1997). The aim was to identify suitable wind sectors and meteorological conditions for flux measurements. These tools were used on data of 18 participating sites. Quality tests were applied on the fluxes of momentum, sensible and latent heat, and on the CO 2 -flux, respectively. The influence of the topography on the vertical wind component was also checked. At many sites the land use around the flux towers is not homogeneous or the fetch may not be large enough. So the relative contribution of the land use type intended to be measured was also investigated. Thus the developed tool allows comparative investigations of the measured turbulent fluxes at different sites if using the same technique and algorithms for the determination of the fluxes as well as analyses of potential problems caused by influences of the surrounding land use patterns.

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Structure of Carbon Dioxide Exchange Processes Above a Spruce Forest

Cited by 12 publications

References 17 publications

Aerodynamic gradient measurements of the NH<sub>3</sub>-HNO<sub>3</sub>-NH<sub>4</sub>NO<sub>3</sub> triad using a wet chemical instrument: an analysis of precision requirements and flux errors

Aerodynamic gradient measurements of the NH<sub>3</sub>-HNO<sub>3</sub>-NH<sub>4</sub>NO<sub>3</sub> triad using a wet chemical instrument: an analysis of precision requirements and flux errors

Organised Motion in a Tall Spruce Canopy: Temporal Scales, Structure Spacing and Terrain Effects

Quality analysis applied on eddy covariance measurements at complex forest sites using footprint modelling

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Structure of Carbon Dioxide Exchange Processes Above a Spruce Forest

Cited by 12 publications

References 17 publications

Aerodynamic gradient measurements of the NH&lt;sub&gt;3&lt;/sub&gt;-HNO&lt;sub&gt;3&lt;/sub&gt;-NH&lt;sub&gt;4&lt;/sub&gt;NO&lt;sub&gt;3&lt;/sub&gt; triad using a wet chemical instrument: an analysis of precision requirements and flux errors

Aerodynamic gradient measurements of the NH&lt;sub&gt;3&lt;/sub&gt;-HNO&lt;sub&gt;3&lt;/sub&gt;-NH&lt;sub&gt;4&lt;/sub&gt;NO&lt;sub&gt;3&lt;/sub&gt; triad using a wet chemical instrument: an analysis of precision requirements and flux errors

Organised Motion in a Tall Spruce Canopy: Temporal Scales, Structure Spacing and Terrain Effects

Quality analysis applied on eddy covariance measurements at complex forest sites using footprint modelling

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Aerodynamic gradient measurements of the NH<sub>3</sub>-HNO<sub>3</sub>-NH<sub>4</sub>NO<sub>3</sub> triad using a wet chemical instrument: an analysis of precision requirements and flux errors

Aerodynamic gradient measurements of the NH<sub>3</sub>-HNO<sub>3</sub>-NH<sub>4</sub>NO<sub>3</sub> triad using a wet chemical instrument: an analysis of precision requirements and flux errors