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Evaluation of optical remote sensing to estimate actual evapotranspiration and canopy conductance

Yebra, Marta; Van Dijk, Albert; Leuning, Ray; Huete, Alfredo; Guerschman , Juan Pablo

Description

We compared estimates of actual evapotranspiration (ET) produced with six different vegetation measures derived from the MODerate resolution Imaging Spectroradiometer (MODIS) and three contrasting estimation approaches using measurements from eddy covariance flux towers at 16 FLUXNET sites located over six different land cover types. The aim was to assess optimal approaches in using optical remote sensing to estimate ET. The first two approaches directly regressed various MODIS vegetation...[Show more]

dc.contributor.authorYebra, Marta
dc.contributor.authorVan Dijk, Albert
dc.contributor.authorLeuning, Ray
dc.contributor.authorHuete, Alfredo
dc.contributor.authorGuerschman , Juan Pablo
dc.date.accessioned2015-12-10T23:11:44Z
dc.identifier.issn0034-4257
dc.identifier.urihttp://hdl.handle.net/1885/63824
dc.description.abstractWe compared estimates of actual evapotranspiration (ET) produced with six different vegetation measures derived from the MODerate resolution Imaging Spectroradiometer (MODIS) and three contrasting estimation approaches using measurements from eddy covariance flux towers at 16 FLUXNET sites located over six different land cover types. The aim was to assess optimal approaches in using optical remote sensing to estimate ET. The first two approaches directly regressed various MODIS vegetation indices (VIs) and products such as leaf area index (LAI) and fraction of photosynthetically active radiation (fPAR) with ET and evaporative fraction (EF). In the third approach, the Penman-Monteith (PM) equation was inverted to obtain surface conductance (Gs), for dry plant canopies. The Gs values were then regressed against the MODIS data products and used to parameterize the PM equation for retrievals of ET. Jack-Knife cross-validation was used to evaluate the various regression models against observed ET. The PM-Gs approach provided the lowest root mean square error (RMSE), and highest determination coefficients (R2) across all sites, with an average RMSE=38Wm-2 and R2=0.72. Direct regressions of observed ET against the VIs resulted in an average RMSE=60Wm-2 and R2=0.22, while the EF regressions an average RMSE=42Wm-2 and R2=0.64. The MODIS LAI and fPAR product produced the poorest estimates of ET (RMSE>44Wm-2 and R2<0.6); while the VIs each performed best for some of the land cover types. The enhanced vegetation index (EVI) produced the best ET estimates for evergreen needleleaf forest (RMSE=28.4Wm-2, R2=0.66). The normalized difference vegetation index (NDVI) best estimated ET in grassland (RMSE=23.8Wm-2 and R2=0.68), cropland (RMSE=29.2Wm-2 and R2=0.86) and woody savannas (RMSE=25.4Wm-2 and R2=0.82), while the VI-based crop coefficient (Kc) yielded the best estimates for evergreen and deciduous broadleaf forests (RMSE=27Wm-2 and R2=0.7 in both cases). Using the ensemble-average of ET as estimated using NDVI, EVI and Kc we computed global grids of dry canopy conductance (Gc) from which annual statistics were extracted to characterise different functional types. The resulting Gc values can be used to parameterize land surface models.
dc.publisherElsevier
dc.sourceRemote Sensing of Environment
dc.subjectKeywords: EF; ET; FPAR; LAI; MODIS; Penman Monteith; Surface conductance; Vegetation index; Evapotranspiration; Forestry; Mean square error; Radiometers; Rain; Regression analysis; Remote sensing; Satellite imagery; Vegetation; Water supply; Estimation; canopy exch EF; ET; FPAR; LAI; MODIS; Penman Monteith; Surface conductance; Vegetation indices
dc.titleEvaluation of optical remote sensing to estimate actual evapotranspiration and canopy conductance
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume129
dc.date.issued2013
local.identifier.absfor090905 - Photogrammetry and Remote Sensing
local.identifier.absfor050102 - Ecosystem Function
local.identifier.absfor060705 - Plant Physiology
local.identifier.ariespublicationu4279067xPUB852
local.type.statusPublished Version
local.contributor.affiliationYebra, Marta, CSIRO
local.contributor.affiliationVan Dijk, Albert, College of Medicine, Biology and Environment, ANU
local.contributor.affiliationLeuning, Ray, CSIRO
local.contributor.affiliationHuete, Alfredo, CSIRO
local.contributor.affiliationGuerschman , Juan Pablo, CSIRO
local.description.embargo2037-12-31
local.bibliographicCitation.startpage250
local.bibliographicCitation.lastpage261
local.identifier.doi10.1016/j.rse.2012.11.004
local.identifier.absseo960907 - Forest and Woodlands Water Management
local.identifier.absseo960303 - Climate Change Models
local.identifier.absseo829805 - Management of Water Consumption by Plant Production
dc.date.updated2016-02-24T10:53:14Z
local.identifier.scopusID2-s2.0-84870666828
local.identifier.thomsonID000315308300020
CollectionsANU Research Publications

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