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Scalar similarity for relaxed Eddy accumulation methods

Title data

Ruppert, Johannes ; Thomas, Christoph ; Foken, Thomas:
Scalar similarity for relaxed Eddy accumulation methods.
In: Boundary-Layer Meteorology. Vol. 120 (2006) Issue 1 . - pp. 39-63.
ISSN 1573-1472
DOI: https://doi.org/10.1007/s10546-005-9043-3

Abstract in another language

The relaxed eddy accumulation (REA) method allows the measurement of trace gas fluxes when no fast sensors are available for eddy covariance measurements. The flux parameterisation used in REA is based on the assumption of scalar similarity, i. e. similarity of the turbulent exchange of two scalar quantities. In this study changes in scalar similarity between carbon dioxide, sonic temperatureand water vapour were assessed using scalar correlation coefficients and spectral analysis. The infuence on REA measurements was assessed by simulation. The evaluation is based on data recorded during experiments over grassland, irrigated cotton plantation and spruce forest. Scalar similarity between carbon dioxide, sonic temperature and water vapour showed a distinct diurnal pattern and change within the day. Poor scalar similarity was found to be linked to dissimilarities in the energy contained in the low frequency part of the turbulent spectra (< 0.01 Hz).The simulations of REA showed signifcant change in b-factors throughout the diurnal course. The b-factor is part of the REA parameterisation scheme and describes a relation between the concentration diverence and the flux of a trace gas. The diurnal course of b-factors for carbon dioxide, sonic temperature and water vapour matched well. Relative °ux errors induced in REA by varying scalar similarity were generally below +/-10 %. Systematic underestimation of the flux of up to -40% was found for the use of REA applying a hyperbolic deadband (HREA).This underestimation was addressed to poor scalar similarity between the scalar of interest and the scalar used as proxy for the deadband definition.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER33801
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Micrometeorology
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Micrometeorology > Professorship Micrometeorology - Univ.-Prof. Dr. Christoph K. Thomas
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 24 Apr 2015 11:56
Last Modified: 24 Apr 2015 11:56
URI: https://eref.uni-bayreuth.de/id/eprint/11449