ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-12-1923-2012 Coupling processes and exchange of energy and reactive and non-reactive trace gases at a forest site – results of the EGER experiment Foken T. 1 5 Meixner F. X. 2 4 Falge E. 2 Zetzsch C. 3 5 Serafimovich A. 1 5 Bargsten A. 2 Behrendt T. 2 Biermann T. 1 Breuninger C. 2 Dix S. 1 6 Gerken T. 1 Hunner M. 1 6 Lehmann-Pape L. 2 Hens K. 2 Jocher G. 1 7 Kesselmeier J. 2 Lüers J. 1 5 Mayer J.-C. 2 Moravek A. 2 Plake D. 2 Riederer M. 1 Rütz F. 1 Scheibe M. 2 8 Siebicke L. 1 9 Sörgel M. 3 Staudt K. 1 10 Trebs I. 2 Tsokankunku A. 2 Welling M. 2 Wolff V. 2 10 Zhu Z. 2 11 University of Bayreuth, Department of Micrometeorology, 95440 Bayreuth, Germany Max-Planck-Institute of Chemistry, Biogeochemistry Department, P.O. Box 3060, 55020 Mainz, Germany University of Bayreuth, Atmospheric Chemistry Research Laboratory, 95440 Bayreuth, Germany University of Zimbabwe, Department of Physics, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe Member of Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany now at: TÜV Süd Industrie Service GmbH Wind Cert Services, Ludwig-Eckert-Straße 10, 93049 Regensburg, Germany now at: Alfred-Wegener Institute for Polar and Marine Research, Telegrafenberg A43, 14473 Potsdam, Germany now at: German Aerospace Center (DLR), Institute of Atmospheric Physics, Münchner Straße 20, 82234 Oberpfaffenhofen-Wessling, Germany now at: Institut National de la Recherche Agronomique (INRA), BP 709, 97387 Cedex Kourou, French Guiana now at: Agroscope ART Research Station, Reckenholzstrasse 191, 8046 Zürich, Switzerland now at: Institute for Geographic Sciences and Natural Resources Research, ChineseAcademy of Sciences (CAS), A11 Datun Road, Anwai, Beijing 100101, China 17 02 2012 12 4 1923 1950 Copyright: © 2012 T. Foken et al. 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/12/1923/2012/acp-12-1923-2012.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/12/1923/2012/acp-12-1923-2012.pdf

To investigate the energy, matter and reactive and non-reactive trace gas exchange between the atmosphere and a spruce forest in the German mountain region, two intensive measuring periods were conducted at the FLUXNET site DE-Bay (<i>Waldstein-Weidenbrunnen</i>) in September/October 2007 and June/July 2008. They were part of the project "ExchanGE processes in mountainous Regions" (EGER). Beyond a brief description of the experiment, the main focus of the paper concerns the coupling between the trunk space, the canopy and the above-canopy atmosphere. Therefore, relevant coherent structures were analyzed for different in- and above canopy layers, coupling between layers was classified according to already published procedures, and gradients and fluxes of meteorological quantities as well as concentrations of non-reactive and reactive trace compounds have been sorted along the coupling classes. Only in the case of a fully coupled system, it could be shown, that fluxes measured above the canopy are related to gradients between the canopy and the above-canopy atmosphere. Temporal changes of concentration differences between top of canopy and the forest floor, particularly those of reactive trace gases (NO, NO<sub>2</sub>, O<sub>3</sub>, and HONO) could only be interpreted on the basis of the coupling stage. Consequently, only concurrent and vertically resolved measurements of micrometeorological (turbulence) quantities and fluxes (gradients) of trace compounds will lead to a better understanding of the forest-atmosphere interaction.

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