Status for: Evapotranspiration (MOD16)

 
General Accuracy Statement

Stage 3 validation has been achieved for the MODIS Collection 6 evapotranspiration product (MOD16).

The mean absolute errors are 24% of the ET measurements, within the 10-30% range of the accuracy of ET observations (Mu et al, 2011). The correlation coefficients of the tower-specific improved ET estimates with the ET measurements averaged over all the available days is 0.86 when driven by NASA Goddard's Global Modeling and Assimilation Office (GMAO) meteorological data.

The MODIS evapotranspiration (ET) algorithm is based on the logic of the Penman-Monteith equation, which uses daily meteorological reanalysis data and 8-day remotely sensed vegetation property dynamics from MODIS as input. MOD16 Collection 6 products include terrestrial ecosystem evapotranspiration (ET), latent heat flux (LE), potential ET (PET), and potential LE (PLE) data layers and are produced at 500m spatial resolution.

To validate the MOD16 algorithm, we used the observed latent heat flux for 46 field-based eddy covariance flux towers over the 11 years (2000 to 2010), driven by two sets of meteorological data: tower-based meteorological data and GMAO meteorological data (Mu et al, 2011).

Micrometeorological tower sites use the eddy covariance technique to measure exchanges of carbon dioxide, water vapor, and energy between terrestrial ecosystems and the atmosphere. Their data have been used extensively for direct validation and optimization of many global water and carbon models. Figure 1 shows an example the validation carried out of the MOD16 ET algorithm for two selected sites, while Figure 2 compares average ET estimates by MOD16 and the 46 micrometeorological tower sites.

MODIS ET val plot
Figure 1. The ET measurements (black dots, OBS), the ET estimates driven by flux tower measured meteorological data (red lines) and GMAO meteorological data (blue lines) over 2000-2006 at seven tower sites, Donaldson (a) and LBA Tapajos KM67 Mature Forest (b). From Mu et al (2011).

 
MODIS ET tower met vs GMAO plot
Figure 2. Comparisons of the average ET observations to the average daily ET estimates across all the available days at the 46 flux tower sites. These data were created using (1) tower-specific meteorology (left) and (2) the global GMAO meteorology (right) with the MOD16 ET algorithm. The solid grey lines represent that the ratio of ET estimates to ET measurements is 1.0 and the solid black lines are the regression of the ET estimates to measurements. (from Mu et al 2011)


Product status updated:  August 2019
Product version:  Collection 6
 
Supporting Studies:

Title: Comparison of the performance of latent heat flux products over southern hemisphere forest ecosystems: estimating latent heat flux error structure using in situ measurements and the triple collocation method
Author: Barraza Bernadas, V., Grings, F., Restrepo-Coupe, N. and Huete, A.
Source: International Journal of Remote Sensing, 39:19, 6300-6315, DOI: 10.1080/01431161.2018.1458348
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Title: Multi-scale evaluation of global gross primary productivity and evapotranspiration products derived from Breathing Earth System Simulator (BESS)
Author: Jiang, C. and Ryu, Y.
Source: Remote Sensing of Environment, 186, pp.528-547
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Title: Development of a coupled carbon and water model for estimating global gross primary productivity and evapotranspiration based on eddy flux and remote sensing data
Author: Zhang, Y., Song, C., Sun, G., Band, L.E., McNulty, S., Noormets, A., Zhang, Q. and Zhang, Z.
Source: Agricultural and forest meteorology, 223, pp.116-131
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Title: Water balance_based actual evapotranspiration reconstruction from ground and satellite observations over the conterminous United States
Author: Wan, Z., Zhang, K., Xue, X., Hong, Z., Hong, Y. and Gourley, J.J.
Source: Water Resources Research, 51(8), pp.6485-6499
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Title: Comparing evapotranspiration from eddy covariance measurements, water budgets, remote sensing, and land surface models over Canada
Author: Wang, S., Pan, M., Mu, Q., Shi, X., Mao, J., Brümmer, C., Jassal, R.S., Krishnan, P., Li, J. and Black, T.A.
Source: Journal of Hydrometeorology, 16(4), pp.1540-1560
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Title: Comparison of different evaporation estimates over the African continent
Author: Trambauer, P., Dutra, E., Maskey, S., Werner, M., Pappenberger, F., Van Beek, L.P.H. and Uhlenbrook, S.
Source: Hydrology and Earth System Sciences, 18(1), p.193
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Title: Assessment of the MODIS global evapotranspiration algorithm using eddy covariance measurements and hydrological modelling in the Rio Grande basin
Author: Ruhoff, A.L., Paz, A.R., Aragao, L.E.O.C., Mu, Q., Malhi, Y., Collischonn, W., Rocha, H.R. and Running, S.W.
Source: Hydrological Sciences Journal, 58(8), pp.1658-1676
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Title: Uncertainty in evapotranspiration from land surface modeling, remote sensing, and GRACE satellites.
Author: Long, D., Longuevergne, L. and Scanlon, B.R.
Source: Water Resources Research, 50(2), pp.1131-1151
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Title: A comprehensive evaluation of two MODIS evapotranspiration products over the conterminous United States: Using point and gridded FLUXNET and water balance ET
Author: Velpuri, N.M., Senay, G.B., Singh, R.K., Bohms, S. and Verdin, J.P.
Source: Remote Sensing of Environment, 139, pp.35-49
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Title: Global estimates of evapotranspiration for climate studies using multi-sensor remote sensing data: Evaluation of three process-based approaches
Author: Vinukollu, R.K., Wood, E.F., Ferguson, C.R. and Fisher, J.B.
Source: Remote Sensing of Environment, Volume 115, Issue 3, Pages 801-823
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Title: Improvements to a MODIS global terrestrial evapotranspiration algorithm
Author: Mu, Q., Zhao, M., & Running, S. W.
Source: J. Geophys. Res., 112, G01012, doi:10.1029/2006JG000179
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