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Multitemporal fluctuations in L-Band Backscatter from a japanese forest / Manabu Watanabe in IEEE Transactions on geoscience and remote sensing, vol 53 n° 11 (November 2015)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 53 n° 11 (November 2015) . - pp 5799 - 5813 Titre : Multitemporal fluctuations in L-Band Backscatter from a japanese forest Type de document : Article/Communication Auteurs : Manabu Watanabe, Auteur ; Takeshi Motohka, Auteur ; Tomohiro Shiraishi, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 5799 - 5813 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] bande L [Termes IGN] biomasse forestière [Termes IGN] coefficient de rétrodiffusion [Termes IGN] constante diélectrique [Termes IGN] données multitemporelles [Termes IGN] forêt [Termes IGN] image ALOS [Termes IGN] image radar moirée [Termes IGN] Japon Résumé : (Auteur) The temporal variations (diurnal and annual) in arboreal (εTree) and bare soil (εSoil) dielectric constants and their correlation with precipitation were examined for several trees in Japan. A significant (1 σ (standard deviation) and 2 σ) εTree increase is observed after rainfall at 89.8% and 90.5% probability. However, rainfall does not always induce significant εTree increases. Rainfall of more than 5 mm/day can induce 1 σ εTree Tree increase at a 59.6% probability. In order to examine whether the increase in εTree affects the L-band σ0 variation in a forest, the four-year temporal variation of the L-band backscattering coefficient (σ0) was estimated from observations by the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar. Observed maximum absolute deviations from the mean over the forest area were 1.0 and 1.2 dB for σHH0 and σHV0, respectively, and 4.0 and 3.0 dB over open land. σ0 and rainfall correlations show that εTree and σForest0 are proportional to precipitation integrated over seven or eight days; εSoil and σOpen land0 are proportional to precipitation integrated over three days. This finding indicates that εTree variations influence σForest areas0. A stronger correlation between σHV0 and precipitation is observed in several sites with low σHV0, where less biomass is expected, and several sites with high σHV0, where more biomass is expected. A weaker correlation between σHV0 and precipitation is observed for several sites with high σ- sub>HV0. These differences may be explained by the different contributions of double bounce scattering and potential transpiration, which is a measure of the ability of the atmosphere to remove water from the surface through the processes of transpiration. The two other results were as follows: 1) The functional relation between aboveground biomass and σ0 showed dependence on precipitation data, this being an effect connected with seasonal changes of the εTree. This experiment reinforces the fact that the dry season is preferable for retrieval of woody biomass from inversion of the functional dependence of SAR backscatter and for avoiding the influence of rainfall. 2) The complex dielectric constant for a tree trunk, which is measured between 0.2 and 6 GHz, indicates that free water is dominant in the measured tree. Numéro de notice : A2015-774 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2015.2415832 Date de publication en ligne : 05/06/2015 En ligne : https://doi.org/10.1109/TGRS.2015.2415832 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=78832 [article]

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