%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Garcia, M.
%A Sandholt, I.
%A Ceccato, P.
%A Ridler, M.
%A Mougin, E.
%A Kergoat, L.
%A Morillas, L.
%A Timouk, Franck
%A Fensholt, R.
%A Domingo, F.
%T Actual evapotranspiration in drylands derived from in-situ and satellite data : assessing biophysical constraints
%D 2013
%L fdi:010060729
%G ENG
%J Remote Sensing of Environment
%@ 0034-4257
%K Evapotranspiration ; Surface temperature ; Priestley-Taylor ; Thermal inertia ; MSG-SEVIRI ; Water-limited ecosystems ; MODIS
%K MALI
%M ISI:000315546900008
%P 103-118
%R 10.1016/j.rse.2012.12.016
%U https://www.documentation.ird.fr/hor/fdi:010060729
%> https://www.documentation.ird.fr/intranet/publi/2013/04/010060729.pdf
%V 131
%W Horizon (IRD)
%X Improving regional estimates of actual evapotranspiration (lambda E) in water-limited regions located at climatic transition zones is critical. This study assesses an lambda E model (PT-JPL model) based on downscaling potential evapotranspiration according to multiple stresses at daily time-scale in two of these regions using MSG-SEVIRI (surface temperature and albedo) and MODIS products (NDVI, LAI and f(PAR)). An open woody savanna in the Sahel (Mali) and a Mediterranean grassland (Spain) were selected as test sites with Eddy Covariance data used for evaluation. The PT-JPL model was modified to run at a daily time step and the outputs from eight algorithms differing in the input variables and also in the formulation of the biophysical constraints (stresses) were compared with the lambda E from the Eddy Covariance. Model outputs were also compared with other modeling studies at similar global chyland ecosystems. The novelty of this paper is the computation of a key model parameter, the soil moisture constraint, relying on the concept of apparent thermal inertia (f(SM-ATI)) computed with surface temperature and albedo observations. Our results showed that f(SM-ATI) from both in-situ and satellite data produced satisfactory results for lambda E at the Sahelian savanna, comparable to parameterizations using field-measured Soil Water Content (SWC) with r(2) greater than 0.80. In the Mediterranean grasslands however, with much lower daily lambda E values, model results were not as good as in the Sahel (r(2)= 0.57-0.31) but still better than reported values from more complex models applied at the site such as the Two Source Model (TSM) or the Penman-Monteith Leuning model (PML). PT-JPL-daily model with a soil moisture constraint based on apparent thermal inertia, f(SM-ATI) offers great potential for regionalization as no field-calibrations are required and water vapor deficit estimates, required in the original version, are not necessary, being air temperature and the available energy (Rn-G) the only input variables required, apart from routinely available satellite products.
%$ 126 ; 072