 |
| Titel |
Intercomparison and assessment of turbulent and physiological exchange parameters of grassland |
| VerfasserIn |
E. Nemitz, K. J. Hargreaves, A. Neftel, B. Loubet, P. Cellier, J. R. Dorsey, M. Flynn, A. Hensen, T. Weidinger, R. Meszaros, L. Horvath, U. Dämmgen, C. Frühauf, F. J. Löpmeier, M. W. Gallagher, M. A. Sutton |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 8 ; Nr. 6, no. 8 (2009-08-07), S.1445-1466 |
| Datensatznummer |
250003940
|
| Publikation (Nr.) |
 copernicus.org/bg-6-1445-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| 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 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
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 (λE) is larger,
with standard deviations of averages of 18%. The dataset averaged over
the different instruments fails to close the energy budget by 20%,
significantly larger than the uncertainties in the individual flux
corrections. However, if the largest individual turbulent flux estimates are
considered, energy closure can be achieved, indicating that the closure gap
is within the spread of the measurements. The uncertainty in λE
feeds results in an uncertainty in the bulk stomatal resistance, which
further adds to the uncertainties 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. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|