A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...
A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...
A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...
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S<strong>at</strong>ellite observ<strong>at</strong>ions of inter-annual vari<strong>at</strong>ion of veget<strong>at</strong>ion productivity and w<strong>at</strong>ercontent in Legal <strong>Amazon</strong> <strong>Basin</strong> during 1998-2001Xiangming Xiao, Qingyuang Zhang, Rob Braswell, Stephen Frolking, Stephen Boles, andBerrien Moore IIIAbstractUniversity of New Hampshire, Durham, NH 03824, USAMailing address of corresponding author:Complex Systems Research Center, Institute for <strong>the</strong> Study of Earth, Oceans and Space,University of New Hampshire, Durham, NH 03824, USAEmail addresses: xiangming.xiao@unh.eduClim<strong>at</strong>e and land use change are two major factors th<strong>at</strong> drive sp<strong>at</strong>ial and temporal vari<strong>at</strong>ions ofveget<strong>at</strong>ion in <strong>the</strong> Legal <strong>Amazon</strong> <strong>Basin</strong>. In an effort to characterize interannual vari<strong>at</strong>ion ofveget<strong>at</strong>ion in <strong>the</strong> basin, we have assembled <strong>the</strong> 10-day composite images from <strong>the</strong> SPOT-4VEGETATION sensor (VGT) over <strong>the</strong> period of April 1-10, 1998 to November 11- 20, 2001 for<strong>the</strong> entire basin. The VGT sensor has 4 spectral bands (blue, red, near infrared and short-waveinfrared) and provides daily observ<strong>at</strong>ion of <strong>the</strong> globe <strong>at</strong> 1-km sp<strong>at</strong>ial resolution. In this study ourobjective is to develop better understanding of veget<strong>at</strong>ion indices in rel<strong>at</strong>ion to clim<strong>at</strong>e vari<strong>at</strong>ion.Three remote sensing proxies were calcul<strong>at</strong>ed and compared: Normalized Difference Veget<strong>at</strong>ionIndex (NDVI), Enhanced Veget<strong>at</strong>ion Index (EVI), and Normalized Difference W<strong>at</strong>er Index(NDWI). The NDVI and EVI are <strong>the</strong> proxies for veget<strong>at</strong>ion productivity. The EVI includesinform<strong>at</strong>ion from <strong>the</strong> blue band to account for residual <strong>at</strong>mospheric contamin<strong>at</strong>ion (e.g., aerosolsand w<strong>at</strong>er vapor) and soil/veget<strong>at</strong>ion background, while <strong>the</strong> NDVI does not. The NDWI is <strong>the</strong>proxy for veget<strong>at</strong>ion w<strong>at</strong>er content. Anomalies of NDWI, NDVI and EVI over 1998-2001 werecalcul<strong>at</strong>ed and compared <strong>with</strong> anomalies of precipit<strong>at</strong>ion and temper<strong>at</strong>ure from <strong>the</strong> N<strong>at</strong>ionalClim<strong>at</strong>e D<strong>at</strong>a Center Global History Clim<strong>at</strong>e Network. At <strong>the</strong> basin scale, <strong>the</strong> NDWI anomaly iscorrel<strong>at</strong>ed well <strong>with</strong> <strong>the</strong> precipit<strong>at</strong>ion anomaly, indic<strong>at</strong>ing th<strong>at</strong> NDWI has a potential forassessing veget<strong>at</strong>ion w<strong>at</strong>er content in <strong>the</strong> tropical ecosystems. The temporal p<strong>at</strong>tern of EVIanomaly is different from <strong>the</strong> NDVI anomaly, particularly in 1998 and 1999. Consistent <strong>with</strong> <strong>the</strong>earlier studies, this basin-scale study also suggests EVI might be a more useful altern<strong>at</strong>iveveget<strong>at</strong>ion index than NDVI for veget<strong>at</strong>ion monitoring.
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