HR: 1340h
AN: B43B-0269    [Abstracts]
TI: Observed trends of NDVI and climate over the Amazon basin
AU: * Hashimoto, H
EM: hirofumi.hashimoto@gmail.com
AF: California State University, 100 Campus Center, Seaside, CA 93955 United States
AU: * Hashimoto, H
EM: hirofumi.hashimoto@gmail.com
AF: NASA Ames Research Center, NASA Ames Research Center, Moffett Field, CA 94035 United States
AU: Ichii, K
B43B-0269 AF: San Jose State University, 1 Washington Square, San Jose, CA 95192 United States
AU: Ichii, K
B43B-0269 AF: NASA Ames Research Center, NASA Ames Research Center, Moffett Field, CA 94035 United States
AU: Nemani, R R
B43B-0269 AF: NASA Ames Research Center, NASA Ames Research Center, Moffett Field, CA 94035 United States
AU: Myneni, R B
B43B-0269 AF: Boston University, 8 Saint Mary's Street, Boston, MA 02215 United States
AB: The carbon balance of Amazon rainforests plays a key role in global carbon budget. Plot-level observations as well as modeling studies indicate that there has been an increasing trend in the growth rate of these forests. Because the observations of both climate and ecosystems are too sparse, the mechanisms of the forest response to climate change in Amazon basin are still not well known. For the last two decades, the interannual variation of modeled Net primary Production (NPP) in Amazon basin showed increasing trend corresponding to the increasing trend of the incoming shortwave radiation. The questions of this study are to understand whether satellites can detect the modeled/observed trend in vegetation growth, and what changes in climate can explain the increasing trend in vegetation activity. To analyze the trend of Amazon vegetation for the last two decades, we used Normalized Difference Vegetation Index (NDVI) from Global Inventory Modeling and Mapping Studies (GIMMS) and Pathfinder AVHRR Land (PAL) data sets. We used multiple datasets where possible to get a consistent picture of changes over Amazon. The climate variables include rainfall (CRU, CMAP, GPCP, and TRMM), incoming short wave radiation (ISCCP, NCEP2), precipitable water (NVAP, NCEP2, ISCCP), cloud cover (ISCCP, NCEP2). We calculated the trend for all the variables in Amazon basin for each season. NDVI of GIMMS showed increasing trend for austral summer in Amazon basin. NDVI of PAL data also showed increasing trend for austral summer, but less significant compared to GIMMS dataset. All data directly or indirectly related to solar radiation consistently showed that there has been an increasing trend in incoming shortwave radiation over the past two decades. On the other hand, we could not find any trends in rainfall, possibly due to high interannual variability. Though further investigation is required, it appears that the increasing trend of NDVI could be due to the increasing trend in shortwave radiation enhancing growth in these light-limited ecosystems.
DE: 0426 Biosphere/atmosphere interactions (0315)
SC: Biogeosciences [B]
MN: Fall Meeting 2005