Poster (Scientific congresses and symposiums)
Momentum, sensible heat and CO2 correlation coefficient: what can we learn from 20 years of eddy covariance measurements
Hurdebise, Quentin; De Ligne, Anne; Vincke, Caroline et al.
2017European Goesciences Union General Assembly 2017
 

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Keywords :
Canopy aerodynamic distance; Turbulence; Eddy covariance
Abstract :
[en] Long-term data series of carbon dioxide and other gas exchanges between terrestrial ecosystems and atmosphere become more and more numerous. Long-term analyses of such exchanges require a good understanding of measurement conditions during the investigated period. Independently of climate drivers, measurements may indeed be influenced by measurement conditions themselves subjected to long-term variability due to vegetation growth or set-up changes. The present research refers to the Vielsalm Terrestrial Observatory (VTO) an ICOS candidate site located in a mixed forest (beech, silver fir, Douglas fir, Norway spruce) in the Belgian Ardenne. Fluxes of momentum, carbon dioxide and sensible heat have been continuously measured there by eddy covariance for more than 20 years. During this period, changes in canopy height and measurement height occurred. The correlation coefficients (for momemtum, sensible heat and CO2) and the normalized standard deviations measured for the past 20 years at the Vielsalm Terrestrial Observatory (VTO) were analysed in order to define how the fluxes, independently of climate conditions, were affected by the surrounding environment evolution, including tree growth, forest thinning and tower height change. A relationship between canopy aerodynamic distance and the momentum correlation coefficient was found which is characteristic of the roughness sublayer, and suggests that momentum transport processes were affected by z-d. In contrast, no relationship was found for sensible heat and CO2 correlation coefficients, suggesting that the z-d variability observed did not affect their turbulent transport. There were strong differences in these coefficients, however, between two wind sectors, characterized by contrasted stands (height differences, homogeneity) and different hypotheses were raised to explain it. This study highlighted the importance of taking the surrounding environment variability into account in order to ensure the spatio-temporal consistency of datasets.
Research center :
TERRA Teaching and Research Centre - TERRA
Disciplines :
Physics
Author, co-author :
Hurdebise, Quentin ;  Université de Liège > Ingénierie des biosystèmes (Biose) > Biosystems Dynamics and Exchanges
De Ligne, Anne ;  Université de Liège > Ingénierie des biosystèmes (Biose) > Biosystems Dynamics and Exchanges
Vincke, Caroline;  Université Catholique de Louvain - UCL > Earth and Life Institute > Forest sciences
Heinesch, Bernard  ;  Université de Liège > Ingénierie des biosystèmes (Biose) > Biosystems Dynamics and Exchanges
Aubinet, Marc ;  Université de Liège > Ingénierie des biosystèmes (Biose) > Biosystems Dynamics and Exchanges
Language :
English
Title :
Momentum, sensible heat and CO2 correlation coefficient: what can we learn from 20 years of eddy covariance measurements
Alternative titles :
[fr] Coefficients de correlation pour la quantité de mouvement, la chaleur sensible et le CO2: que peux-t'on apprendre de 20 années de mesures d'Eddy Covariance
Publication date :
24 April 2017
Number of pages :
A0
Event name :
European Goesciences Union General Assembly 2017
Event organizer :
European Geosciences Union
Event place :
Vienna, Austria
Event date :
du 23 avril 2017 au 28 avril 2017
Audience :
International
Name of the research project :
CO2 fluxes interannual variability at the Vielsalm Terrestrial Observatory
Funders :
SPW DG03-DGARNE - Service Public de Wallonie. Direction Générale Opérationnelle Agriculture, Ressources naturelles et Environnement [BE]
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since 03 June 2017

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