An Empirical Algorithm for Estimating Agricultural and Riparian Evapotranspiration Using MODIS Enhanced Vegetation Index and Ground Measurements of ET. I. Description of Method

Remote Sensing

Pamela L. Nagler²  Kiyomi Morino⁴  R. Scott Murray³  John Osterberg¹ 

[1] US Bureau of Reclamation, Denver Federal Center, Denver, CO 80225, USA; E-Mail:;US Geological Survey, Southwest Biological Science Center, Sonoran Desert Research Station, 1110 E. South Campus Drive, Room 123, Tucson, AZ 85721, USA;Environmental Research Laboratory, University of Arizona, 2601 East Airport Drive, Tucson, AZ 85706, USA; E-Mails:;Laboratory of Tree Ring Research, 105 West Stadium, University of Arizona, Tucson, AZ 85721, USA; E-Mail:

关键词: sap flux;    transpiration;    stomatal conductance;    evaporative fraction;    remote sensing;    saltcedar;   

DOI  :  10.3390/rs1041273

来源: mdpi

【 摘 要 】

We used the Enhanced Vegetation Index (EVI) from MODIS to scale evapotranspiration (ET_actual) over agricultural and riparian areas along the Lower Colorado River in the southwestern US. Ground measurements of ET_actual by alfalfa, saltcedar, cottonwood and arrowweed were expressed as fraction of potential (reference crop) ET_o (ET_oF) then regressed against EVI scaled between bare soil (0) and full vegetation cover (1.0) (EVI*). EVI* values were calculated based on maximum and minimum EVI values from a large set of riparian values in a previous study. A satisfactory relationship was found between crop and riparian plant ET_oF and EVI*, with an error or uncertainty of about 20% in the mean estimate (mean ET_actual = 6.2 mm d⁻¹, RMSE = 1.2 mm d⁻¹). The equation for ET_actual was: ET_actual = 1.22 × ET_o-BC × EVI*, where ET_o-BC is the Blaney Criddle formula for ET_o. This single algorithm applies to all the vegetation types in the study, and offers an alternative to ET_actual estimates that use crop coefficients set by expert opinion, by using an algorithm based on the actual state of the canopy as determined by time-series satellite images.

【 授权许可】

CC BY   
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.