Low frequency transports in the atmospheric surface layer over Amazon forest
Celso
Von
Randow, Alterra, The Netherlands, celso.vonrandow@wur.nl
(Presenting)
Bart
Kruijt, Alterra, The Netherlands, bart.kruijt@wur.nl
Bert
Holtslag, Wageningen University, The Netherlands, bert.holtslag@wur.nl
Leonardo
Deane de Abreu
Sá, MPEG, Belém, ldsa@museu-goeldi.br
Antonio
Ocimar
Manzi, INPA, Manaus, manzi@inpa.gov.br
Alessandro
Carioca de
Araujo, Vrije Universiteit, The Netherlands, arau@geo.vu.nl
Antonio
Donato
Nobre, INPE, Sao Jose dos Campos, anobre@ltid.inpe.br
The eddy correlation method is being used in a number of towers in the Amazon forest to study the surface energy and carbon exchange processes which take place over this region. However, recent studies have been indicating the limitations and conceptual uncertainties associated with the method, when applied over complex surfaces such as tall forests or hilly terrain. Especially in the Amazon forest areas, 'low frequency' processes such as deep convection large eddies, roll vortices and local circulations by topography or surface heterogeneity can significantly contribute to the forest-atmosphere total exchange. Two aspects of the problem should be considered. On one hand, we should include all the low frequency motions that carry significant amount to the total mass and energy exchanges in order to close the balances. But, on the other hand, we should study the processes related with the 'local surface' separately: the contribution of the mean flow to the total transport is considered as an advective flux, which is assumed to behave deterministically, while that of the turbulence is regarded as an eddy flux and analysed statistically. Also, to relate the fluxes with the local mean wind shear and temperature stratification (similarity theory, for instance), ideally we would only include the transports on turbulence scales and exclude mesoscale and larger motions. In this work the use of some relationships from surface-layer physics and vegetation physiology is evaluated as potential constraints to separate "locally meaningful" fluxes from mesoscale and other larger processes.
Submetido por Celso Von Randow em 18-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)