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 Printable version |
Mapping of real daily evapotranspiration in the Algerian semiarid environment with satellite Aster data |
Science et changements planétaires / Sécheresse. Volume 19, Number 4, 293-300, octobre-novembre-décembre 2008, Article de recherche
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 Résumé
Article gratuit
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Author(s) : Abderrahmane Hamimed, Rabha Menaa, Mohamed Benslimane, Lamia Bouabdellah |
Summary : The main aim of this study is to estimate real daily evapotranspiration by solving the energy balance equation using a boundary layer pattern based on the SEBAL (Surface Energy Balance Algorithm for Land) approach over heterogeneous terrain with Aster data. Some parameters for assessing crop water stress degree in a pixel by pixel basis were then extracted. The algorithm of resolution of energy balance equation involves NDVI (Normalised Difference Vegetation Index), surface temperature and albedo in the input. To extract the latent heat flux, we estimated the following terms by hierarchical order: the net radiation, the soil heat flux and the sensible heat flux. The latter was calculated from an intermediate flux of momentum. In this part, we exploited and validated the complementarity between albedo and surface temperature in order to detect dry pixels. We then estimated the average of the sensible heat flux density over these dry pixels. The latter value along with use of the boundary layer profile and the coupling surface/boundary layer, which operates in the level of fluxes in the basis of the convective boundary layer, gave us the possibility of extracting the sensible heat flux and consequently dissecting the energy balance equation and assessing the real evapotranspiration. Finally, different moisture indicators were calculated: the evaporative fraction, the Priestley and Taylor parameter and the Bulk surface resistance to evaporation. These calculated indicators facilitate the quantitative diagnosis of moisture stress status in a pixel basis. The instantaneous evaporative fraction, considered similar to its daily counterpart, makes it possible to estimate daily real evapotranspiration. |
Keywords : Algeria, energy balance, evapotranspiration, remote sensing |
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