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Flux contribution of coherent structures and its implications for the exchange of energy and matter in a tall spruce canopy

Titelangaben

Thomas, Christoph ; Foken, Thomas:
Flux contribution of coherent structures and its implications for the exchange of energy and matter in a tall spruce canopy.
In: Boundary-Layer Meteorology. Bd. 123 (2007) Heft 2 . - S. 317-337.
ISSN 1573-1472
DOI: https://doi.org/10.1007/s10546-006-9144-7

Abstract

The flux contribution of coherent structures to the total exchange of energy and matter is investigated in a spruce canopy of moderate density in heterogeneous, complex terrain. The study deploys two methods of analysis to estimate the coherent exchange: conditional averages in combination with wavelet analysis, and quadrant analysis. The data were obtained by high-frequency single-point measurements using sonic anemometers and gas analysers at five observation heights above and within the canopy and subcanopy, and represent a period of up to 2.5 months. The study mainly addresses the momentum transfer and exchange of sensible heat throughout the roughness sublayer, while results are provided for the exchange of carbon dioxide and water vapour above the canopy. The magnitude of the flux contribution of coherent structures largely depends on the method of analysis, and it is demonstrated that these differences are attributed to differences in the sampling strategy between the two methods. Despite the differences, relational properties such as sweep and ejection ratios and the variation of the flux contribution with height were in agreement for both methods. The sweep phase of coherent structures is the dominant process close to and within the canopy, whereas the ejections gain importance with increasing distance to the canopy. The efficiency of the coherent exchange in transporting scalars exceeds that for momentum by a factor of two. The occurrence of coherent structures results in a flux error less than 4% for the eddy-covariance method. Based on the physical processes identified from the analysis of the ejection and sweep phases along the vertical profile in the roughness sublayer, a classification scheme for the identification of exchange regimes is developed. This scheme allows one to estimate the region of the canopy participating in the exchange of energy and matter with the above-canopy air under varying environmental conditions.

Weitere Angaben

Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Zusätzliche Informationen: BAYCEER41784
Institutionen der Universität: Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften > Professur Mikrometeorologie
Forschungseinrichtungen > Forschungszentren > Bayreuther Zentrum für Ökologie und Umweltforschung - BayCEER
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften > Professur Mikrometeorologie > Professur Mikrometeorologie - Univ.-Prof. Dr. Christoph K. Thomas
Fakultäten
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften
Forschungseinrichtungen
Forschungseinrichtungen > Forschungszentren
Titel an der UBT entstanden: Nein
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik
Eingestellt am: 24 Apr 2015 11:56
Letzte Änderung: 16 Jan 2020 08:36
URI: https://eref.uni-bayreuth.de/id/eprint/11442