Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method
In many tropical areas, evapotranspiration is the most important but least known component of the water cycle. An innovative method, named E3S (for EVASPA S-SEBI Sahel), was developed to provide spatially-distributed estimates of daily actual evapotranspiration (ET<sub>d</sub>) from remo...
| Main Authors: | , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2020-01-01
|
| Series: | Remote Sensing |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2072-4292/12/3/380 |
| _version_ | 1828143539277529088 |
|---|---|
| author | Aubin Allies Jérôme Demarty Albert Olioso Ibrahim Bouzou Moussa Hassane Bil-Assanou Issoufou Cécile Velluet Malik Bahir Ibrahim Maïnassara Monique Oï Jean-Philippe Chazarin Bernard Cappelaere |
| author_facet | Aubin Allies Jérôme Demarty Albert Olioso Ibrahim Bouzou Moussa Hassane Bil-Assanou Issoufou Cécile Velluet Malik Bahir Ibrahim Maïnassara Monique Oï Jean-Philippe Chazarin Bernard Cappelaere |
| author_sort | Aubin Allies |
| collection | DOAJ |
| description | In many tropical areas, evapotranspiration is the most important but least known component of the water cycle. An innovative method, named E3S (for EVASPA S-SEBI Sahel), was developed to provide spatially-distributed estimates of daily actual evapotranspiration (ET<sub>d</sub>) from remote sensing data in the Sahel. This 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<sub>d</sub> estimates from a weighted average of evapotranspiration estimated from several EF methods. In this work, the two combined approaches were derived from the simplified surface energy balance index (S-SEBI) model and the EVapotranspiration Assessment from SPAce (EVASPA) tool. Main innovative aspects concern (i) ensemble predictions of ET<sub>d</sub> through the implementation of a dynamic weighting scheme of several evapotranspiration estimations, (ii) epistemic uncertainty of the estimation of ET<sub>d</sub> 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. E3S was applied to MODIS/TERRA and AQUA datasets acquired during the 2005−2008 period over the mesoscale AMMA-CATCH (Analyse Multidisciplinaire de la Mousson Africaine—Couplage de l’Atmosphère Tropicale et du Cycle Hydrologique) observatory in South-West Niger. E3S 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. In 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. The RMSE (root mean square error) from this comparison for E3S’s ET<sub>d</sub> estimates from combined AQUA/TERRA sources was 0.5 mm·day<sup>−1</sup>, and the determination coefficient was 0.90. E3S 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. At the mesoscale, ET<sub>d</sub> estimates were obtained with an average epistemic uncertainty of 0.4 mm·day<sup>−1</sup>. Comparisons with the reference 0.25°-resolution GLEAM (global land evaporation Amsterdam model) product showed good agreement. These results suggested that E3S could be used to produce reliable continuous regional estimations at a kilometric resolution, consistent with land and water management requirements in the Sahel. Moreover, all these innovations could be easily transposed to other contextual approaches. |
| first_indexed | 2024-04-11T20:00:09Z |
| format | Article |
| id | doaj.art-349c436d26574370b12dab91ddeef895 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-04-11T20:00:09Z |
| publishDate | 2020-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-349c436d26574370b12dab91ddeef8952022-12-22T04:05:40ZengMDPI AGRemote Sensing2072-42922020-01-0112338010.3390/rs12030380rs12030380Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual MethodAubin Allies0Jérôme Demarty1Albert Olioso2Ibrahim Bouzou Moussa3Hassane Bil-Assanou Issoufou4Cécile Velluet5Malik Bahir6Ibrahim Maïnassara7Monique Oï8Jean-Philippe Chazarin9Bernard Cappelaere10HydroSciences Montpellier, Univ Montpellier, CNRS, IRD, 300 avenue du Professeur Emile Jeanbrau, 34090 Montpellier, FranceHydroSciences Montpellier, Univ Montpellier, CNRS, IRD, 300 avenue du Professeur Emile Jeanbrau, 34090 Montpellier, FranceEnvironnement Méditerranéen et Modélisation des AgroHydrosystèmes (EMMAH), INRAE, Avignon Université, 228 route de l’Aérodrome Domaine Saint Paul—Site Agroparc, 84914 Avignon, FranceDepartment of Geography, Université Abdou Moumouni de Niamey, Harobanda Quarter, Niamey BP 237, NigerDepartment of Crop Science and Technology, Université Dan Dicko Dankoulodo de Maradi, Maradi BP 465, NigeriEnvironnement Méditerranéen et Modélisation des AgroHydrosystèmes (EMMAH), INRAE, Avignon Université, 228 route de l’Aérodrome Domaine Saint Paul—Site Agroparc, 84914 Avignon, FranceEnvironnement Méditerranéen et Modélisation des AgroHydrosystèmes (EMMAH), INRAE, Avignon Université, 228 route de l’Aérodrome Domaine Saint Paul—Site Agroparc, 84914 Avignon, FranceHydroSciences Montpellier, Univ Montpellier, CNRS, IRD, 300 avenue du Professeur Emile Jeanbrau, 34090 Montpellier, FranceHydroSciences Montpellier, Univ Montpellier, CNRS, IRD, 300 avenue du Professeur Emile Jeanbrau, 34090 Montpellier, FranceHydroSciences Montpellier, Univ Montpellier, CNRS, IRD, 300 avenue du Professeur Emile Jeanbrau, 34090 Montpellier, FranceHydroSciences Montpellier, Univ Montpellier, CNRS, IRD, 300 avenue du Professeur Emile Jeanbrau, 34090 Montpellier, FranceIn many tropical areas, evapotranspiration is the most important but least known component of the water cycle. An innovative method, named E3S (for EVASPA S-SEBI Sahel), was developed to provide spatially-distributed estimates of daily actual evapotranspiration (ET<sub>d</sub>) from remote sensing data in the Sahel. This 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<sub>d</sub> estimates from a weighted average of evapotranspiration estimated from several EF methods. In this work, the two combined approaches were derived from the simplified surface energy balance index (S-SEBI) model and the EVapotranspiration Assessment from SPAce (EVASPA) tool. Main innovative aspects concern (i) ensemble predictions of ET<sub>d</sub> through the implementation of a dynamic weighting scheme of several evapotranspiration estimations, (ii) epistemic uncertainty of the estimation of ET<sub>d</sub> 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. E3S was applied to MODIS/TERRA and AQUA datasets acquired during the 2005−2008 period over the mesoscale AMMA-CATCH (Analyse Multidisciplinaire de la Mousson Africaine—Couplage de l’Atmosphère Tropicale et du Cycle Hydrologique) observatory in South-West Niger. E3S 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. In 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. The RMSE (root mean square error) from this comparison for E3S’s ET<sub>d</sub> estimates from combined AQUA/TERRA sources was 0.5 mm·day<sup>−1</sup>, and the determination coefficient was 0.90. E3S 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. At the mesoscale, ET<sub>d</sub> estimates were obtained with an average epistemic uncertainty of 0.4 mm·day<sup>−1</sup>. Comparisons with the reference 0.25°-resolution GLEAM (global land evaporation Amsterdam model) product showed good agreement. These results suggested that E3S could be used to produce reliable continuous regional estimations at a kilometric resolution, consistent with land and water management requirements in the Sahel. Moreover, all these innovations could be easily transposed to other contextual approaches.https://www.mdpi.com/2072-4292/12/3/380evapotranspiration mappingcontextual approachsahelmodissouthwest niger |
| spellingShingle | Aubin Allies Jérôme Demarty Albert Olioso Ibrahim Bouzou Moussa Hassane Bil-Assanou Issoufou Cécile Velluet Malik Bahir Ibrahim Maïnassara Monique Oï Jean-Philippe Chazarin Bernard Cappelaere Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method Remote Sensing evapotranspiration mapping contextual approach sahel modis southwest niger |
| title | Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method |
| title_full | Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method |
| title_fullStr | Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method |
| title_full_unstemmed | Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method |
| title_short | Evapotranspiration Estimation in the Sahel Using a New Ensemble-Contextual Method |
| title_sort | evapotranspiration estimation in the sahel using a new ensemble contextual method |
| topic | evapotranspiration mapping contextual approach sahel modis southwest niger |
| url | https://www.mdpi.com/2072-4292/12/3/380 |
| work_keys_str_mv | AT aubinallies evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT jeromedemarty evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT albertolioso evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT ibrahimbouzoumoussa evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT hassanebilassanouissoufou evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT cecilevelluet evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT malikbahir evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT ibrahimmainassara evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT moniqueoi evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT jeanphilippechazarin evapotranspirationestimationinthesahelusinganewensemblecontextualmethod AT bernardcappelaere evapotranspirationestimationinthesahelusinganewensemblecontextualmethod |