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Tomas F. Domingues, Joseph A. Berry, Luiz A. Martinelli, Jean P. H. B. Ometto, and James R. Ehleringer

; Williams et al. 1998 ; Asner et al. 2000 ; Botta and Foley 2002 ; Chou et al. 2002 ; Zhan et al. 2003 ; Santos and Costa 2004 ). While some studies identified rain forest Amazonian ecosystems as sinks for atmospheric carbon ( Grace et al. 1995 ; Malhi et al. 1998 ; Phillips et al. 1998 ; Andreae et al. 2002 ; Araújo et al. 2002 ; Carswell et al. 2002 ), other studies indicate an equilibrium situation or even that these ecosystems are a source of CO 2 to the atmosphere ( Chou et al. 2002

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Wilfrid Schroeder, Jeffrey T. Morisette, Ivan Csiszar, Louis Giglio, Douglas Morton, and Christopher O. Justice

:// ). During these months, a large high pressure system tends to cover the region, inhibiting precipitation and reducing relative humidity due to the subsidence of dry air from the upper levels of the atmosphere ( Figueroa and Nobre 1990 ; Nobre et al. 1998 ). These circulation patterns result in the retention of smoke emitted by burning over a large horizontal expanse, reducing visibility to the point of closing airports and causing respiratory problems among local populations ( Reinhardt et al. 2001

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Gregory P. Asner, David E. Knapp, Amanda N. Cooper, Mercedes M. C. Bustamante, and Lydia P. Olander

canopy tropical forests. Science 284 : 1832 – 1835 . Duivenvoorden , J. F. 1996 . Patterns of tree species richness in rain forests of the middle Caqueta area, Colombia, NW Amazonia. Biotropica 28 : 142 – 158 . Ferreira , L. G. , H. Yoshioka , A. Huete , and E. E. Sano . 2003 . Seasonal landscape and spectral vegetation index dynamics in the Brazilian Cerrado: An analysis within the Large-Scale Biosphere–Atmosphere Experiment in Amazônia (LBA). Remote Sens. Environ. 87

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Carlos M. Souza Jr., Dar A. Roberts, and AndréL. Monteiro

parameters of the atmospheric correction model were determined by a trial-and-error sensitivity analysis of a dark object reflectance (a lake). The final parameters were estimated when the expected reflectance values of the dark object were found. The fixed water vapor was 40 mm, and image atmosphere visibility was 25 km. The other images ( Table 2 ) were intercalibrated to the reflectance image using a relative radiometric calibration approach ( Roberts et al. 1998 ; Furby and Campbell 2001 ). This

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Douglas C. Morton, Ruth S. DeFries, Yosio E. Shimabukuro, Liana O. Anderson, Fernando Del Bon Espírito-Santo, Matthew Hansen, and Mark Carroll

, College Park, for 2001 and 2002 by subsetting global products for each test scene (M. Hansen and M. Carroll 2004, personal communication). Daily MOD09 data were used as algorithm inputs and to derive additional input products. Red and near-infrared (NIR) reflectance bands and the derived normalized difference vegetation index [NDVI; calculated as (Red − NIR)/(Red + NIR)] at 250-m resolution were evaluated in this study. Blue and middle-infrared (MIR) reflectance bands, resampled from 500- to 250-m

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