Article (Scientific journals)
Direct advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forests
Aubinet, Marc; Feigenwinter, Christian; Heinesch, Bernard et al.
2010In Agricultural and Forest Meteorology, 150 (5), p. 655-664
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Keywords :
Advection; Forests; CO2 fluxes; Eddy covariance
Abstract :
[en] The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time conditions, in an attempt to improve NEE estimates. Four towers were arranged in a square around a main tower, with the sides of the square about 100 m long. Equipped with 16 sonic anemometers and [CO2] sampling points, the towers were installed to measure vertical and horizontal advection of [CO2]. Vertical turbulent fluxes were measured by an eddy covariance system at the top of the main tower. The results showed that horizontal advection varied greatly from site to site and from one wind sector to another, the highest values being reached when there were large friction velocities and fairly unstable conditions. There was less variation in vertical advection, the highest values being reached when there were low friction velocities and stable conditions. The night-time NEE estimates deduced from the mass balance were found to be incompatible with biologically driven fluxes because (i) they varied strongly from one wind sector to another and this variation could not be explained in terms of a response of the biologic flux to climate, (ii) their order of magnitude was not realistic and (iii) they still showed a trend vs. friction velocity. From a critical analysis of the measurement and data treatment we concluded that the causes of the problem are related to the representativeness of the measurement (control volume size, sampling resolution) or the hypotheses underlying the derivation of the [CO2] mass balance (ignoring the horizontal turbulent flux divergence). This suggests that the improvement of eddy flux measurements by developing an advection completed [CO2] mass balance at night would be practically difficult. (C) 2010 Elsevier B.V. All rights reserved.
Disciplines :
Environmental sciences & ecology
Author, co-author :
Aubinet, Marc ;  Université de Liège - ULiège > Sciences et technologie de l'environnement > Physique des bio-systèmes
Feigenwinter, Christian;  Université de Liège - ULiège - Gembloux Agro-Bio Tech > Sciences et Technologies de l'environnement > Physique des Bio-systèmes
Heinesch, Bernard  ;  Université de Liège - ULiège > Sciences et technologie de l'environnement > Physique des bio-systèmes
Bernhofer, C.;  TU Dresden (TUD) Institute of Hydrology and Meteorology > Meteorology
Canepa, E.;  CNR-ISMAR, Genova, Italy
Lindroth, A.;  University of Lund (LUND), Sweden > GeoBiosphere Science Centre, Physical Geography and Ecosystems Analysis
Montagnani, L.;  Forest Service and Agency for the Environment Autonomous Province of Bolzano, Bolzano, Italy
Rebmann, C.;  Max Planck Institute for Biogeochemistry (MPI-BGC), Jena, Germany
Sedlak, P.;  Institute of Atmospheric Physics, Prague > Academy of Sciences of the Czech Republic
Van Gorsel, E.;  CSIRO, Marine and Atmospheric Research, Canberra, ACT, Australia
Language :
English
Title :
Direct advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forests
Publication date :
15 May 2010
Journal title :
Agricultural and Forest Meteorology
ISSN :
0168-1923
eISSN :
1873-2240
Publisher :
Elsevier Science, Amsterdam, Netherlands
Special issue title :
Sp. Iss. SI
Volume :
150
Issue :
5
Pages :
655-664
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 30 June 2010

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