992 resultados para 42-380
Resumo:
The euphotic depth (Zeu) is a key parameter in modelling primary production (PP) using satellite ocean colour. However, evaluations of satellite Zeu products are scarce. The objective of this paper is to investigate existing approaches and sensors to estimate Zeu from satellite and to evaluate how different Zeu products might affect the estimation of PP in the Southern Ocean (SO). Euphotic depth was derived from MODIS and SeaWiFS products of (i) surface chlorophyll-a (Zeu-Chla) and (ii) inherent optical properties (Zeu-IOP). They were compared with in situ measurements of Zeu from different regions of the SO. Both approaches and sensors are robust to retrieve Zeu, although the best results were obtained using the IOP approach and SeaWiFS data, with an average percentage of error (E) of 25.43% and mean absolute error (MAE) of 0.10 m (log scale). Nevertheless, differences in the spatial distribution of Zeu-Chla and Zeu-IOP for both sensors were found as large as 30% over specific regions. These differences were also observed in PP. On average, PP based on Zeu-Chla was 8% higher than PP based on Zeu-IOP, but it was up to 30% higher south of 60°S. Satellite phytoplankton absorption coefficients (aph) derived by the Quasi-Analytical Algorithm at different wavelengths were also validated and the results showed that MODIS aph are generally more robust than SeaWiFS. Thus, MODIS aph should be preferred in PP models based on aph in the SO. Further, we reinforce the importance of investigating the spatial differences between satellite products, which might not be detected by the validation with in situ measurements due to the insufficient amount and uneven distribution of the data.
Resumo:
El período político que se abre en septiembre de 1930 hasta el 4 de junio de 1943, es conocido por distintos nombres: "década infame", "fraude patriótico" o "restauración oligárquica". Lo cierto que todas estas denominaciones aluden a la conformación de los distintos sectores que usufructuaron el poder, a sus relaciones sociales y económicas y al método que eligieron para llegar a los cargos.
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Fil: Steszak, Germán. Universidad Nacional de Cuyo
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Fil: Pró, Diego F.. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras. Instituto de Filosofía Argentina y Americana
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Fil: Mendoza, José María Felipe. Universidad Católica Argentina