Normalized Difference Vegetation Index (NDVI)
Description
The shortage of water available to vegetation in a drought limits the growth and productivity of vegetation. Chlorophyll, which is the pigment in plant leaves, strongly absorbs red light (from 0.6 to 0.7 µm) for photosynthesis. The cell structure of the leaves strongly reflects near-infrared light (from 0.7 to 1.1 µm). The magnitude of absorption and reflection of red and near-infrared light is strongly a function of leaf area and vegetation vigor. Satellite imagery has long been used to evaluate differences in plant reflectance and to determine their spatial distribution. A common satellite image index of vegetation vigor is the Normalized Difference Vegetation Index (NDVI) (Huete et al., 1985; Jackson and Huete, 1991), which ranges from -1 to 1, with ~ 0.5 to 1 representing high vegetation vigor. Effects of drought can be visualized through computing time series and spatial anomalies of NDVI.
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