Intraseasonal Variability of the Surface Fluxes in Santarém
Pedro
Leite
Silva Dias, IAG/USP, pldsdias@master.iag.usp.br
(Presenting)
Maria Isabel
Vitorino, IAG/USP, isabel@model.iag.usp.br
Humberto
Ribeiro da
Rocha, IAG/USP, humberto@model.iag.usp.br
Scott
Dennis
Miller, University of California, sdmiller@uci.edu
Michael
L.
Goulden, University of California, mgoulden@uci.edu
The time variability of the rainfall over large areas in the tropics is modulated by intra-seasonal variability in the 20-60 day range. Most of the intra-seasonal signal is associated to an eastward propagating wave with maximum activity in the equatorial region although significant impact is also found at higher latitudes. Although the Amazon is not particularly influenced by the intraseasonal variability, some effect can be detected in the wind field associated with changes in the intensity of the trades winds and therefore on the moisture inflow in the Amazon. Changes in solar radiation in the intraseasonal band can also be detected in the Amazon, due to changes in the cloudiness. This paper explores the intraseasonal variability of meteorological parameters and surface fluxes in the Santarém area, based on the Net Ecosystem Exchange (NEE) calculated for each half-hour interval as the sum of the turbulent CO2 flux at 64 m (the eddy flux) and the change in the amount of CO2 in the air column beneath 64 m (the storage flux). The measurements were made
from a 67-m-tall, 46-cm-triangular-cross-section tower micrometeorological tower data. The wavelet analysis using Morlet functions (Morlet, 1982, Grossman and Morlet,1984) was used to decompose the variability signal present in the data into their intraseasonal multiple time scales components. This method is appropriated for non stationary processes. Although the intraseasonal variability in the Amazon convection, estimated from the outgoing longwave radiation (OLR) is not particularly strong, compared to other tropical regions, a significant signal seems evident in the CO2 flux time series. It is hypothesized that the vegetation primarily responds to the intraseasonal signal in the short wave.
Submetido por Pedro Leite Silva Dias em 25-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)