865 resultados para Hierarchical sampling


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We combined the analysis of sediment trap data and satellite-derived sea surface chlorophyll to quantify the amount of organic carbon export to the deep sea in the upwelling induced high production area off northwest Africa. In contrast to the generally global or basin-wide adoption of export models, we used a regionally fitted empirical model. Furthermore, the application of our model was restricted to a dynamically defined region of high chlorophyll concentration in order to restrict the model application to an environment of more homogeneous export processes. We developed a correlation-based approximation to estimate the surface source area for a sediment trap deployed from 11 June 1998 to 7 November 1999 at 21.25°N latitude and 20.64°W longitude off Cape Blanc. We also developed a regression model of chlorophyll and export of organic carbon to the 1000 m depth level. Carbon export was calculated for an area of high chlorophyll concentration (>1 mg/m**3) adjacent to the coast on a daily basis. The resulting zone of high chlorophyll concentration was 20,000-800,000 km**2 large and yielded a yearly export of 1.123 to 2.620 Tg organic carbon. The average organic carbon export within the area of high chlorophyll concentration was 20.6 mg/m**2d comparable to 13.3 mg/m**2d as found in the sediment trap results if normalized to the 1000 m level. We found strong interannual variability in export. The period autumn 1998 to summer 1999 was exceeding the mean of the other three comparable periods by a factor of 2.25. We believe that this approach of using more regionally fitted models can be successfully transferred even to different oceanographic regions by selecting appropriate definition criteria like chlorophyll concentration for the definition of an area to which it is applicable.

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Apart from common cases of differential argument marking, referential hierarchies affect argument marking in two ways: (a) through hierarchical marking, where markers compete for a slot and the competition is resolved by a hierarchy, and (b) through co-argument sensitivity, where the marking of one argument depends on the properties of its co-argument. Here we show that while co-argument sensitivity cannot be analyzed in terms of hierarchical marking, hierarchical marking can be analyzed in terms of co-argument sensitivity. Once hierarchical effects on marking are analyzed in terms of co-argument sensitivity, it becomes possible to examine alignment patterns relative to referential categories in exactly the same way as one can examine alignment patterns relative to referential categories in cases of differential argument marking and indeed any other condition on alignment (such as tense or clause type). As a result, instances of hierarchical marking of any kind turn out not to present a special case in the typology of alignment, and there is no need for positing an additional non-basic alignment type such as “hierarchical alignment”. While hierarchies are not needed for descriptive and comparative purposes, we also cast doubt on their relevance in diachrony: examining two families for which hierarchical agreement has been postulated, Algonquian and Kiranti, we find only weak and very limited statistical evidence for agreement paradigms to have been shaped by a principled ranking of person categories.

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Includes bibliographical references.