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AGU: Geophysical Research Letters

 

Keywords

  • Amazon
  • drought
  • sensitivity

Index Terms

  • Biogeosciences: Remote sensing
  • Biogeosciences: Biosphere/atmosphere interactions
  • Biogeosciences: Data sets
  • Biogeosciences: Computational methods and data processing

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L05401, 5 PP., 2010
doi:10.1029/2009GL042154

Amazon forests did not green-up during the 2005 drought

Arindam Samanta

Department of Geography and Environment, Boston University, Boston, Massachusetts, USA

Sangram Ganguly

BAERI, NASA Ames Research Center, Moffett Field, California, USA

Hirofumi Hashimoto

Department of Science and Environmental Policy, California State University, Monterey Bay, Seaside, California, USA

Sadashiva Devadiga

Sigma Space Corporation, at NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

Eric Vermote

Department of Geography, University of Maryland, College Park, Maryland, USA

Yuri Knyazikhin

Department of Geography and Environment, Boston University, Boston, Massachusetts, USA

Ramakrishna R. Nemani

Biospheric Science Branch, NASA Ames Research Center, Moffett Field, California, USA

Ranga B. Myneni

Department of Geography and Environment, Boston University, Boston, Massachusetts, USA

The sensitivity of Amazon rainforests to dry-season droughts is still poorly understood, with reports of enhanced tree mortality and forest fires on one hand, and excessive forest greening on the other. Here, we report that the previous results of large-scale greening of the Amazon, obtained from an earlier version of satellite-derived vegetation greenness data - Collection 4 (C4) Enhanced Vegetation Index (EVI), are irreproducible, with both this earlier version as well as the improved, current version (C5), owing to inclusion of atmosphere-corrupted data in those results. We find no evidence of large-scale greening of intact Amazon forests during the 2005 drought - approximately 11%–12% of these drought-stricken forests display greening, while, 28%–29% show browning or no-change, and for the rest, the data are not of sufficient quality to characterize any changes. These changes are also not unique - approximately similar changes are observed in non-drought years as well. Changes in surface solar irradiance are contrary to the speculation in the previously published report of enhanced sunlight availability during the 2005 drought. There was no co-relation between drought severity and greenness changes, which is contrary to the idea of drought-induced greening. Thus, we conclude that Amazon forests did not green-up during the 2005 drought.

Received 11 December 2009; accepted 26 January 2010; published 5 March 2010.

Citation: Samanta, A., S. Ganguly, H. Hashimoto, S. Devadiga, E. Vermote, Y. Knyazikhin, R. R. Nemani, and R. B. Myneni (2010), Amazon forests did not green-up during the 2005 drought, Geophys. Res. Lett., 37, L05401, doi:10.1029/2009GL042154.

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