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Canopy directional emissivity: comparison between models / J.A. Sobrino in Remote sensing of environment, vol 99 n° 3 (30/11/2005)  

Public [article]  inRemote sensing of environment > vol 99 n° 3 (30/11/2005) . - pp 304 - 314 Titre : Canopy directional emissivity: comparison between models Type de document : Article/Communication Auteurs : J.A. Sobrino, Auteur ; J.C. Jimenez-Munoz, Auteur ; W. Verhoef, Auteur Année de publication : 2005 Article en page(s) : pp 304 - 314 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] analyse comparative [Termes IGN] couvert végétal [Termes IGN] emissivité [Termes IGN] évapotranspiration [Termes IGN] modèle de transfert radiatif [Termes IGN] radiance [Termes IGN] rayonnement infrarouge thermique [Termes IGN] température au sol Résumé : (Auteur) Land surface temperature plays an important role in many environmental studies, as for example the estimation of heat fluxes and evapotranspiration. In order to obtain accurate values of land surface temperature, atmospheric, emissivity and angular effects should be corrected. This paper focuses on the analysis of the angular variation of canopy emissivity, which is an important variable that has to be known to correct surface radiances and obtain surface temperatures. Emissivity is also involved in the atmospheric corrections since it appears in the reflected, downwelling atmospheric term. For this purpose, five different methods for simulating directional canopy emissivity have been analyzed and compared. The five methods are composed of two geometrical models, developed by Sobrino et al. and Snyder and Wan, in which the vegetation is considered as an opaque medium, and three are based on radiative transfer models, developed by François et al., Snyder and Wan and Verhoef et al., in which the vegetation is considered as a turbid medium. Over surfaces with sparse and low vegetation cover, high angular variations of canopy emissivity are obtained, with differences between at-nadir view and 80° of 0.03. Over fully vegetated surfaces angular effects on emissivity are negligible when radiative transfer models are applied, so in these situations the angular variations on emissivity are not critical on the retrieved land surface temperature from remote sensing data. Angular variations on emissivity are lower when the emissivity of the soil and the emissivity of the vegetation are closer. All the models considered assume Lambertian behaviour for the soil and the leaves. This assumption is also discussed, showing a different behaviour of directional canopy emissivity when a non-Lambertian soil is considered. Numéro de notice : A2005-459 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2005.09.005 En ligne : https://doi.org/10.1016/j.rse.2005.09.005 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27595 [article]