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Intercomparison and assessment of turbulent and physiological exchange parameters of grassland

Nemitz, E.; Hargreaves, K.J.; Neftal, A.; Loubet, B.; Cellier, P.; Dorsey, J.R.; Flynn, M.; Hensen, A.; Weidunger, T.; Meszaros, R.; Horvath, L.; Dammgen, U.; Fruhauf, C.; Lopmeier, F.J.; Gallagher, M.W.; Sutton, M.A.. 2009 Intercomparison and assessment of turbulent and physiological exchange parameters of grassland. Biogeosciences Discussions, 6 (1). 241-290.

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Abstract/Summary

Commonly, the micrometeorological parameters that underline the calculations of surface atmosphere exchange fluxes (e.g. friction velocity and sensible heat flux) and parameters used to model exchange fluxes with SVAT-type parameterisations (e.g. latent 5 heat flux and canopy temperature) are measured with a single set of instrumentation and are analysed with a single methodology. This paper evaluates uncertainties in these measurements with a single instrument, by comparing the independent results from nine different institutes during the international GRAMINAE integrated field experiment over agricultural grassland near Braunschweig, Lower Saxony, Germany. The 10 paper discusses uncertainties in measuring friction velocity, sensible and latent heat fluxes, canopy temperature and investigates the energy balance closure at this site. Although individual 15-min flux calculations show a large variability between the instruments, when averaged over the campaign, fluxes agree within 2% for momentum and 11% for sensible heat. However, the spread in estimates of latent heat flux (E) is 15 larger, with standard deviations of averages of 18%. While the dataset averaged over the different instruments fails to close the energy budget by 30%, if the largest turbulent fluxes are considered, near perfect energy closure can be achieved, suggesting that most techniques underestimate E in particular. The uncertainty in E feeds results in an uncertainty in the bulk stomatal resistance, which further adds to the uncertainties 20 in the estimation of the canopy temperature that controls the exchange. The paper demonstrated how a consensus dataset was derived, which is used by the individual investigators to calculate fluxes and drive their models.

Item Type: Publication - Article
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon > BG01.1 UK nitrogen and sulphur compounds
CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon > BG01.3 Nitroeurope NEU advanced flux network, fluxes pools and budgets
CEH Sections: Billett (to 30 Nov 2013)
Additional Information. Not used in RCUK Gateway to Research.: Open Access Journal. The full text of this paper is available from the journal website. http://www.biogeosciences-discuss.net/volumes_and_issues.html
NORA Subject Terms: Atmospheric Sciences
Date made live: 01 Jun 2009 09:20
URI: http://nora.nerc.ac.uk/id/eprint/5534

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