Quantitative improvement in the estimates of NDVI values from remotely sensed data by correcting thin cirrus scattering effects

The Normalized Difference Vegetation Index (NDVI) has been used extensively for remote sensing of vegetation for many years. This index uses radiances or reflectances from a red channel at 0.66 mum and near-infrared channel a t 0.86 mum. Thin cirrus clouds frequently contaminate remotely sensed data acquired from aircraft and satellite platforms. They introduce additional s cattered radiances to the 0.66-mum and 0.86-mum channels. To obtain unbiase d estimates of NDVI values from remotely sensed data, the cirrus scattering effects must be removed. We recently have developed an empirical technique for removing thin cirrus scattering effects using the sensitive 1.375-mum cirrus-detecting channel. In this article, we demonstrate that the estimate s of NDVI values van be improved quantitatively after the removal of thin c irrus effects. Pairs of spectral imaging data, with and nearly without thin cirrus contamination, acquired with the Airborne Visible Infrared Imaging Spectrometer (AVIRIS) are used in this study. Because a special channel cen tered at 1.375 mum has been implemented on the Moderate Resolution Imaging Spectrometer (MODIS) for detecting thin cirrus clouds from space, it is pos sible to remove thin cirrus scattering effects from MODIS channels below 1 mum and to yield improved global estimates of NDVI values from MODIS data. (C) 2000 Published by Elsevier Science Ireland Ltd.