Reference : Direct advection measurements do not help to solve the night-time CO2 closure problem...
Scientific journals : Article
Life sciences : Environmental sciences & ecology
Direct advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forests
Aubinet, Marc mailto [Université de Liège - ULg > Sciences et technologie de l'environnement > Physique des bio-systèmes >]
Feigenwinter, Christian [Université de Liège - ULg - Gembloux Agro-Bio Tech > Sciences et Technologies de l'environnement > Physique des Bio-systèmes > >]
Heinesch, Bernard mailto [Université de Liège - ULg > 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 > > > > > >]
Agricultural and Forest Meteorology
Elsevier Science
Sp. Iss. SI
Yes (verified by ORBi)
The Netherlands
[en] Advection ; Forests ; CO2 fluxes ; Eddy covariance
[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.
Researchers ; Professionals

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