Flux-variance method estimation of scalar turbulent fluxes above Amazonian rain forest

Eddy-correlation (EC) turbulent scalar flux measurements above the Amazonian rain forest were used to investigate the usefulness of the flux-variance (FV) estimation method in a very abnormal environment (the Amazonian forest canopy has a mean height of 35m; however, some of its higher tree branches have a height of 45m). The data is obtained by instrumental sensors located on a 60m height micrometeorological tower built at the Amazonian Forest Rebio-Jaru Reserve (10º 04' S; 61º 56' W) during the LBA (Large Scale Biosphere Atmosphere Experiment in Amazonia) wet season campaign which is been held from january to march 1999 in brazilian State of Rondonia. In a first step we use turbulent data measured at 67m height and recorded at a sampling rate of 16 Hz to compare the EC flux calculations with the FV estimations ones. In a second step, we use the same EC calculations to compare with FV estimations from data obtained at 55m height, and sampled at 0.1 Hz rate. This has been done because some of the data measured at the higher level of the tower (67m height) were lacking for several time intervals. Some preliminary results showed a very good correlation between the EC and FV flux values but the last ones superestimate flux calculations by a factor of 1.5 when the conventional flux-variance relationships provided by the Monin-Obukhov Similarity Theory are applied. Further a new parameterization relationships for the normalized temperature and specific humidity variances for the Amazonian rain forest surface boundary-layer is proposed by us and some possible physical explanations for these results are also discussed.