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Abstract. Previous field measurements have implied that undisturbed Amazon forests may represent a substantial terrestrial sink for atmospheric carbon dioxide. We investigated this hypothesis using a regional ecosystem model for net primary production (NPP) and soil biogeochemical cycling. Seasonal and interannual controls on net ecosystem production (NEP) were studied with integration of high-resolution (8-km) multiyear satellite data to characterize Amazon land surface properties over time. Background analysis of temporal and spatial relationships between regional rainfall patterns and satellite observations (for vegetation land cover, fire counts, and smoke aerosol effects) reveals several notable patterns in the model driver data. Autocorrelation analysis for monthly vegetation "greenness" index ( Comparisons of NDVI seasonal profiles in areas of the eastern Amazon widely affected by fires (as observed from satellite) suggest that our adjusted AVHRR-NDVI captures year-toyear variation in land cover greenness with minimal interference from small fires and smoke aerosols. Ecosystem model results using this newly generated combination of regional forcing data from satellite suggest that undisturbed Amazon forests can be strong net sinks for atmospheric carbon dioxide, particularly during wet (non E1 Nifio) years. However, drought effects during E1 Nifio years can reduce NPP in primary forests of the eastern Amazon by 10-20%, compared to long-term average estimates of regional productivity.Annual NEP for the region is predicted to range from -0.4 Pg C yr -• (net CO2 source) to 0.5 Pg C yr -• (net CO2 sink), with large interannual variability over the states of Par/t, Maranhao, and Amazonas. As in the case of predicted NPP, it appears that periods of relatively high solar surface irradiance combined with several months of adequate rainfall are required to sustain the forest carbon sink for positive yearly NEP estimates.

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We have investigated global teleconnections of climate to regional satellite-driven observations for prediction of Amazon ecosystem production, in the form of monthly estimates of net carbon exchange over the period 1982-1998 from the NASA-CASA (Carnegie-Ames-Stanford) biosphere model. This model is driven by observed surface climate and monthly estimates of vegetation leaf area index (LAI) and fraction of absorbed PAR (fraction of photosynthetically active radiation, FPAR) generated from the NOAA satellite advanced very high-resolution radiometer (AVHRR) and similar sensors. Land surface AVHRR data processing using modified moderate-resolution imaging spectroradiometer radiative transfer algorithms includes improved calibration for intraand intersensor variations, partial atmospheric correction for gaseous absorption and scattering, and correction for stratospheric aerosol effects associated with volcanic eruptions. Results from our analysis suggest that anomalies of net primary production and net ecosystem production predicted from the NASA-CASA model over large areas of the Amazon region east of 601W longitude are strongly correlated with the Southern Oscillation index. Extensive areas of the south-central Amazon show strong linkages of the FPAR and the NASA-CASA anomaly record to the Arctic Oscillation index, which help confirm a strong relation to southern Atlantic climate anomalies, with associated impacts on Amazon rainfall patterns. Processes are investigated for these teleconnections of global climate to Amazon ecosystem carbon fluxes and regional land surface climate.