Orginal Paper

Boundary-Layer Meteorology

, Volume 122, Issue 2, pp 397-416

First online:

Eddy covariance measurements of carbon dioxide, latent and sensible energy fluxes above a meadow on a mountain slope

  • Albin HammerleAffiliated withInstitut für Ökologie, Universität Innsbruck
  • , Alois HaslwanterAffiliated withInstitut für Ökologie, Universität Innsbruck
  • , Michael SchmittAffiliated withInstitut für Ökologie, Universität Innsbruck
  • , Michael BahnAffiliated withInstitut für Ökologie, Universität Innsbruck
  • , Ulrike TappeinerAffiliated withInstitut für Ökologie, Universität Innsbruck
  • , Alexander CernuscaAffiliated withInstitut für Ökologie, Universität Innsbruck
  • , Georg WohlfahrtAffiliated withInstitut für Ökologie, Universität Innsbruck Email author 

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Abstract

Carbon dioxide, latent and sensible heat fluxes were measured by means of the eddy covariance method above a mountain meadow situated on a steep slope in the Stubai Valley in Austria, based on the hypothesis that, due to the low canopy height, measurements can be made in the shallow equilibrium layer where the wind field exhibits characteristics akin to level terrain. In order to test the validity of this hypothesis and to identify effects of complex terrain in the turbulence measurements, data were subjected to a rigorous testing procedure using a series of quality control measures established for surface-layer flows. The resulting high quality dataset comprised 36% of the original observations, the substantial reduction being mainly due to a change in surface roughness and associated fetch limitations in the wind sector dominating during nighttime and transition periods. The validity of the high quality dataset was further assessed by two independent tests: (i) a comparison with the net ecosystem carbon dioxide exchange measured by means of ecosystem chambers, and (ii) the ability of the eddy covariance measurements to close the energy balance. The net ecosystem CO2 exchange measured by the eddy covariance method agreed reasonably well with ecosystem chamber measurements. The assessment of the energy balance closure showed that there was no significant difference in the correspondence between the meadow on the slope and another one situated on flat ground at the bottom of the Stubai Valley, available energy being underestimated by 28% and 29%, respectively. We thus conclude that, appropriate quality control provided, the eddy covariance measurements made above a mountain meadow on a steep slope are of similar quality as compared to flat terrain.

Keywords

CARBOMONT project Complex terrain Energy balance closure Footprint model Quality control