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| Titel |
EVASPA (EVapotranspiration Assessment from SPAce) tool: overview and first assessments |
| VerfasserIn |
Belen Gallego-Elvira, Albert Olioso, Maria Mira, Sergio Reyes-Castillo, Gilles Boulet, Olivier Marloie, Sebastien Garrigues, Dominique Courault, Marie Weiss |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076720
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| Zusammenfassung |
| Evapotranspiration (ET) is a fundamental variable of the hydrological cycle which plays a
major role on surface water and energy balances. ET estimation is required for irrigation
management, water resources planning and environmental studies. At the local scale ET can
be accurately determined from detailed ground observations (eddy covariance towers,
lysimeters) but at regional scale, numerous time-consuming and expensive installations
would be required. Remote sensing provides spatially distributed cost-effective information
for ET maps production at regional scale.
EVASPA (EVapotranspiration Assessment from SPAce) tool has been developed to
produce ET maps at relevant spatial and time scales for hydrological or agronomical
purposes. The tool includes several ET estimation methods (S-SEBI method, the triangle
approach and aerodynamic equations) and various equations for estimating the required input
information (albedo, net radiation, ground heat flux-¦). Highlighted features of this tool are:
(i) the possibility of integrating data from various remote sensing sensors, (ii) to be easily
adapted to new sensors, (iii) to provide an estimation of uncertainties (thanks to the
combination of the various ET estimates) and (iv) to produce continuous daily ET maps
even for days without available remote sensing images (by means of interpolation
techniques).
To test the tool, ET maps have been produced for the Crau-Camargue pilot site in
south-eastern France. This site is a flat region characterized by highly contrasted wet and dry
areas, with a high diversity of surfaces: irrigated meadows, dry grasslands (steppic
area), saltmarsh scrubs, paddy fields, orchards, etc. Daily ET maps at kilometric
spatial resolution are produced from MODIS data (Moderate Resolution Imaging
Spectroradiometer, platforms Terra and Aqua) and high resolution ET maps with a
hectometric resolution from ETM+ (Enhanced Thematic Mapper Plus, Landsat 7 platform)
when images of the study area are available. Ground data from several surface
energy balance stations deployed in contrasted areas of the pilot site are used to
assess the performance of EVASPA simulations. First evaluations were performed
by (i) comparing net radiation estimation from ETM+ to ground data with errors
lower than 20 Wm-2, (ii) assessing the performances of the procedure used to
interpolate daily ET for days without images with errors around 0.35 mm d-1, and (iii)
comparing evolution of daily ET for the different ecosystems to ground station
measurements showing that estimates were closely following ecosystem ET (error
around 0.5 mm d-1), for some of them in relation to the level of the water table
below.
EVASPA tool is a prototype software developed in MATLAB within the frame of the European project
SIRRIMED1and with
the support of CNES2
through the TOSCA3
research calls. |
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