Vegetation Indices to Aid Areal Evapotranspiration Estimations

Multiyear ~1982–1990! monthly areal evapotranspiration ~AET! was modeled with the Morton approach at the Solar and Meteorological Surface Observation Network stations within the conterminous United States. The AET values were correlated with satellite-derived, monthly maximum-value-composited Normalized Difference Vegetation Indices ~NDVI! at half-degree resolution over the growing season ~April–October!. Generally, the strongest monthly correlation was obtained when the NDVI values were related to the AET estimates of the previous month. Geographically, both the monthly and growing-season averaged NDVI-AET relationships were best over the prairie ~with an r50.6660.21 and 0.5560.22, and a RMSE526.75612.62 and 6.2461.67 mm month, respectively! and worst along the coastline and in the most humid, southeast region of the conterminous United States, where the Morton approach may function