Abstract
Vegetation index is the most practical product of the satellite remote sensing. Recent studies reveal that the vegetation index can be related to the transpiration.
The correlation of seasonal trend and annual integrated values of the Normalized Difference Vegetation Index (NDVI), included in the Global Ecosystem Database supplied by NOAA-EPA, with evapotranspiration estimates are tested to examine the possibility of the vegetation index as a model parameter to estimate areal evapotranspiration.
In the mid latitudes, seasonal trend of monthly NDVIs is well correlated to that of evapotranspiration. Annual integrated NDVIs can be used as the index of evaporation ratio, namely, the ratio of actual to potential evapotranspiration. These results can only be applied in the mid latitudes. There is no clear relationship between NDVI and evapotranspirations in the low latitudinal region, especially in the humid tropics.
