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Evaluation of the relation between evapotranspiration and normalized difference vegetation index for downscaling the simplified surface energy balance model

Jonathan V. Haynes·Gabriel B. Senay
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Abstract

The Simplified Surface Energy Balance (SSEB) model uses satellite imagery to estimate actual evapotranspiration (ET a ) at 1-kilometer resolution. SSEB ET a is useful for estimating irrigation water use; however, resolution limitations restrict its use to regional scale applications. The U.S. Geological Survey investigated the downscaling potential of SSEB ET a from 1 kilometer to 250 meters by correlating ET a with the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer instrument (MODIS). Correlations were studied in three arid to semiarid irrigated landscapes of the Western United States (Escalante Valley near Enterprise, Utah; Palo Verde Valley near Blythe, California; and part of the Columbia Plateau near Quincy, Washington) during several periods from 2002 to 2008. Irrigation season ET a -NDVI correlations were lower than expected, ranging from R 2 of 0.20 to 0.61 because of an eastward 2–3 kilometer shift in ET a data. The shift is due to a similar shift identified in the land-surface temperature (LST) data from the MODIS Terra satellite, which is used in the SSEB model. Further study is needed to delineate the Terra LST shift, its effect on SSEB ET a , and the relation between ET a and NDVI.

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Jonathan V. Haynes, Gabriel B. Senay. 2012. Evaluation of the relation between evapotranspiration and normalized difference vegetation index for downscaling the simplified surface energy balance model. https://doi.org/10.3133/sir20125197

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