Article (Scientific journals)
Comparing CO2 storage and advection conditions at night at different carboeuroflux sites
Aubinet, Marc; Berbigier, P.; Bernhofer, C. H. et al.
2005In Boundary-Layer Meteorology, 116 (1), p. 63-94
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Keywords :
advection; CO2 storage; forest ecosystems
Abstract :
[en] Anemometer and CO2 concentration data from temporary campaigns performed at six CARBOEUROFLUX forest sites were used to estimate the importance of non-turbulent fluxes in nighttime conditions. While storage was observed to be significant only during periods of both low turbulence and low advection, the advective fluxes strongly influence the nocturnal CO2 balance, with the exception of almost flat and highly homogeneous sites. On the basis of the main factors determining the onset of advective fluxes, the 'advection velocity', which takes net radiation and local topography into account, was introduced as a criterion to characterise the conditions of storage enrichment/depletion. Comparative analyses of the six sites showed several common features of the advective fluxes but also some substantial differences. In particular, all sites where advection occurs show the onset of a boundary layer characterised by a downslope flow, negative vertical velocities and negative vertical CO2 concentration gradients during nighttime. As a consequence, vertical advection was observed to be positive at all sites, which corresponds to a removal of CO2 from the ecosystem. The main differences between sites are the distance from the ridge, which influences the boundary-layer depth, and the sign of the mean horizontal CO2 concentration gradients, which is probably determined by the source/sink distribution. As a consequence, both positive and negative horizontal advective fluxes (corresponding respectively to CO2 removal from the ecosystem and to CO2 supply to the ecosystem) were observed. Conclusive results on the importance of non-turbulent components in the mass balance require, however, further experimental investigations at sites with different topographies, slopes, different land covers, which would allow a more comprehensive analysis of the processes underlying the occurrence of advective fluxes. The quantification of these processes would help to better quantify nocturnal CO2 exchange rates.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Aubinet, Marc ;  Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech
Berbigier, P.
Bernhofer, C. H.
Cescatti, A.
Feigenwinter, C.
Granier, A.
Grunwald, T. H.
Havrankova, K.
Heinesch, Bernard  ;  Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech
Longdoz, Bernard  
Marcolla, B.
Montagnani, L.
Sedlak, P.
More authors (3 more) Less
Language :
English
Title :
Comparing CO2 storage and advection conditions at night at different carboeuroflux sites
Publication date :
2005
Journal title :
Boundary-Layer Meteorology
ISSN :
0006-8314
eISSN :
1573-1472
Publisher :
Springer Science & Business Media B.V.
Volume :
116
Issue :
1
Pages :
63-94
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 08 December 2009

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