Energy closure test in central Amazon: sensitivity to the angle of attack corrections
Alessandro
Carioca de
Araujo, Vrije Universiteit Amsterdam, arau@geo.vu.nl
(Presenting)
John
H. C.
Gash, CEH, jhg@ceh.ac.uk
Jan
A
Elbers, Alterra, Jan.Elbers@wur.nl
Albertus
Johannes
Dolman, Vrije Universiteit Amsterdam, han.dolman@geo.falw.vu.nl
Maarten
J
Waterloo, Vrije Universiteit Amsterdam, watm@geo.vu.nl
Bart
Kruijt, Alterra, Bart.Kruijt@wur.nl
Eddy
Moors, Alterra, Eddy.Moors@wur.nl
Celso
Von
Randow, Alterra, celso.vonrandow@wur.nl
Antonio
Donato
Nobre, Inpa, anobre27@yahoo.com
Nowadays, the eddy covariance technique is being used worldwide by several projects, e.g. Ameriflux, AsiaFlux, Euroflux, LBA, SiberiaFlux, aiming to cover the main terrestrial ecosystems and their responses to climate change. Regarding the partitioning of the net available energy (Rn) at the surface into the fluxes of sensible (H) and latent heat (LE), in the majority of the sites the energy balance do not close. The energy closure tests is 80%, in average. Since June 1999, H and LE fluxes have been measured at two meteorological towers in the same forest ecosystem, in the Manaus-LBA site, using the Gill sonic anemometer to measure the 3D wind components. Recently, Gash et al. (2004) evaluated that this type of sensor may produce different responses according to its angle of attack, which can affect the fluxes. Prior to this study, the energy closure test for Manaus were 75% and 81%, for K34 and C14 towers, respectively. The AltEddy software, which now contains the Gash’s correction, was used to reprocess the raw data. Comparisons were made to evaluate the a priori and a posteriori fluxes. The energy closure test and carbon dioxide flux increased by 6-8%, in average. It seems that the H and LE fluxes are clustered in two areas, one at relatively low Rn values, and other at high Rn values.
Submetido por Alessandro Carioca de Araújo em 25-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)