@article{fdi:010077972,
  title = {{E}vapotranspiration estimation in the {S}ahel using a new ensemble-contextual method},
  author = {{A}llies, {A}. and {D}emarty, {J}{\'e}rome and {O}lioso, {A}. and {M}oussa, {I}. {B}. and {I}ssoufou, {H}. {B}. {A}. and {V}elluet, {C}ecile and {B}ahir, {M}. and {M}ainassara, {I}. and {O}i, {M}onique and {C}hazarin, {J}ean-{P}hilippe and {C}appelaere, {B}ernard},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n many tropical areas, evapotranspiration is the most important but least known component of the water cycle. {A}n innovative method, named {E}3{S} (for {EVASPA} {S}-{SEBI} {S}ahel), was developed to provide spatially-distributed estimates of daily actual evapotranspiration ({ET}d) from remote sensing data in the {S}ahel. {T}his new method combines the strengths of a contextual approach that is used to estimate the evaporative fraction ({EF}) from surface temperature vs. albedo scatterograms and of an ensemble approach that derives {ET}d estimates from a weighted average of evapotranspiration estimated from several {EF} methods. {I}n this work, the two combined approaches were derived from the simplified surface energy balance index ({S}-{SEBI}) model and the {EV}apotranspiration {A}ssessment from {SPA}ce ({EVASPA}) tool. {M}ain innovative aspects concern (i) ensemble predictions of {ET}d through the implementation of a dynamic weighting scheme of several evapotranspiration estimations, (ii) epistemic uncertainty of the estimation of {ET}d from the analysis of the variability of evapotranspiration estimates, and (iii) a new cloud filtering method that significantly improves the detection of cloud edges that negatively affect {EF} determination. {E}3{S} was applied to {MODIS}/{TERRA} and {AQUA} datasets acquired during the 2005-2008 period over the mesoscale {AMMA}-{CATCH} ({A}nalyse {M}ultidisciplinaire de la {M}ousson {A}fricaine-{C}ouplage de l'{A}tmosphere {T}ropicale et du {C}ycle {H}ydrologique) observatory in {S}outh-{W}est {N}iger. {E}3{S} estimates of instantaneous and daily available energy, evaporative fraction, and evapotranspiration were evaluated at a local scale based on two field-monitored plots representing the two main ecosystem types in the area-a millet crop and a fallow savannah bush. {I}n addition to these ground-based observations, the local scale evaluation was performed against continuous simulations by a locally-calibrated soil-vegetation-atmosphere transfer model for the two plots. {T}he {RMSE} (root mean square error) from this comparison for {E}3{S}'s {ET}d estimates from combined {AQUA}/{TERRA} sources was 0.5 mmday(-1), and the determination coefficient was 0.90. {E}3{S} significantly improved representation of the evapotranspiration seasonality, compared with a classical implementation of {S}-{SEBI} or with the original {EVASPA}'s non-weighted ensemble scheme. {A}t the mesoscale, {ET}d estimates were obtained with an average epistemic uncertainty of 0.4 mmday(-1). {C}omparisons with the reference 0.25 degrees-resolution {GLEAM} (global land evaporation {A}msterdam model) product showed good agreement. {T}hese results suggested that {E}3{S} could be used to produce reliable continuous regional estimations at a kilometric resolution, consistent with land and water management requirements in the {S}ahel. {M}oreover, all these innovations could be easily transposed to other contextual approaches.},
  keywords = {evapotranspiration mapping ; contextual approach ; {S}ahel ; {MODIS} ; southwest {N}iger ; {NIGER} ; {ZONE} {SAHELIENNE}},
  booktitle = {},
  journal = {{R}emote {S}ensing},
  volume = {12},
  numero = {3},
  pages = {art. 380 [34 ]},
  year = {2020},
  DOI = {10.3390/rs12030380},
  URL = {https://www.documentation.ird.fr/hor/fdi:010077972},
}