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Scientific Investigations Report 2012–5197

Groundwater Resources Program

Evaluation of the Relation between Evapotranspiration and Normalized Difference Vegetation Index for Downscaling the Simplified Surface Energy Balance Model

By Jonathan V. Haynes and Gabriel B. Senay

Thumbnail of and link to report PDF (1.2 MB)Abstract

The Simplified Surface Energy Balance (SSEB) model uses satellite imagery to estimate actual evapotranspiration (ETa) at 1-kilometer resolution. SSEB ETa 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 ETa from 1 kilometer to 250 meters by correlating ETa 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 ETa-NDVI correlations were lower than expected, ranging from R2 of 0.20 to 0.61 because of an eastward 2–3 kilometer shift in ETa 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 ETa, and the relation between ETa and NDVI.

First posted September 18, 2012

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Suggested citation:

Haynes, J.V., and Senay, G.B., 2012, Evaluation of the relation between evapotranspiration and normalized difference vegetation index for downscaling the simplified surface energy balance model: U.S. Geological Survey Scientific Investigations Report 2012-5197, 8 p.



Contents

Abstract

Introduction

Purpose and Scope

Simplified Surface Energy Balance

Methods

Results

Summary

References Cited


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