Data/hora: 24/06/2024 11:00:39

Biblioteca(s): | Embrapa Cerrados.
Data corrente: | 26/03/2002
Data da última atualização: | 26/03/2002
Autoria: | MORAN, M. S.; HYMER, D. C.; JIUAGO QI; SANO, E. E.
Título: | Soil moisture evaluation using multi-temporal synthetic aperture radar (SAR) in semiarid rangeland.
Ano de publicação: | 2000
Fonte/Imprenta: | Agricultural and Forest Meteorology, Amsterdam, v. 105, p. 69-80, 2000.
Idioma: | Inglês
Conteúdo: | There have been several efforts to utilize satelite based synthetic aperture radar (SAR) measurements to determine surface soil moisture (to 5 cm ) conditions of rangeland regions. The results have be mixed since the relation between the SAR signal and surface soil moisture is confunded by variations in topographic features, surface routghness and vegetation density. We designed na experiment to investigate the sensitivity of C-band SAR backscatter to surface soil moisture in a semiarid rangeland and to test a data-fusion approach based on both optical (Landsat TM) and radar (ERS-2SAR) measurements to improve regional estimates of surface soil moisture content. The data fusion approach utilized the difference between dry and wet season SAR to normalize roughness effects,k and utilized surface reflectance in optical wavelengths to account for differences in vegetation density. We focused the study on three flat, uniformly vegetated sites of known surface roughness, monitored variations in surface soil moisture, vegetation density and SAR signal over time, and obtained eight optical/SAR image pairs throughout the dry and wet seasons. For these sparsely vegetated sites durind this dry year (1997), we found that the SAR signal was not significantly attenuated by sparse green vegetation cover (green leaf area index menor 0.35) and dense standing brown vegetation cover (brown leaf area index up to 1.5). Consequently, the optical data was not required for these application, and the approach could be implemented by simply taking the difference between the dry and wet season SAR. For a data set of eight dates at three study sites, we confirmed that the relation between and was strong and significant 0.93. This study also raised two concerns: the overall sensitivity of SAR was relatively low, and and (2) the approach required a high level of accuracy in the estimate of green leaf area level that may not be obtainable with standard optical remote sensing algorithms. In any case, the positivy results from this study should encourage the use of a multi temporal SAR and optical/SAR fusion for monitoring semiarid range conditions, and improving management of scarce resources.
Palavras-Chave: | Rada; Regiao semi-arida; Semiarid zonesr.
Thesagro: | Umidade do Solo.
Thesaurus Nal: | soil water content.
Categoria do assunto: | --
Registro original: | Embrapa Cerrados (CPAC)
Exemplares: | CPAC - (20970-1) - UPC - SP - -- - CRI5787 -  - CRI5787 - DIS