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1.
J. E. Pinzón C. E. Puente M. B. Parlange W. Eichinger 《Boundary-Layer Meteorology》1995,76(4):323-347
Accurate and fast-response measurements of space-time observations of specific humidity were made above a drying land surface at the University of California at Davis, using the Los Alamos water Raman-lidar. In an attempt to quantify the space-time intermittency features of turbulent flows in the lower atmosphere, a multifractal analysis of these water vapour measurements was performed. The structure of the specific humidity, (x, t), was analyzed quantifying a scalar gradient measure
both in time and space, for all possible one-dimensional cuts, i.e.
and
. The results confirm the multifractal nature of this scalar gradient measure (a type of scalar dissipation rate) and show that humidity measurements at fixed times (x) are more intermittent (e.g. have less entropy dimension) than those at fixed locations in space (t). Similar multifractal behaviour of the spatial data, with and without a transformation from the observed wind velocities, supports the validity of Taylor's hypothesis for the studied fields. 相似文献
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A new methodology to classify European North-East Atlantic transitional waters into ecological types has been developed based on the most important hydrological and morphological features that are likely to determine the ecology of aquatic systems in transitional waters. Hydrological indicators help identifying if a transitional water area is dominated by fresh or sea water and/or by intertidal or subtidal areas, while morphological indicators allow an estimation of the complexity of the transitional water and the diversity of the habitats involved. Twelve transitional waters of the southern Bay of Biscay were classified using this methodology and the five hydro-morphological types obtained were validated with benthic macro-invertebrate data. Transitional waters with a complex morphology showed the highest values of species diversity, while those with a smaller tidal influence showed lower species diversity. The ‘Scrobicularia’ and ‘Abra’ assemblages, previously identified in the study area, were found to be related to different types of transitional waters. The ‘Abra’ assemblage only appeared in estuaries with a complex morphology and dominated by tidal influences, while the ‘Scrobicularia’ assemblage was detected in all the transitional waters except for a single coastal lagoon. This classification of transitional waters may therefore be useful to establish the biological reference conditions needed for European Directives. 相似文献
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C. E. Puente O. Robayo B. Sivakumar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2001,15(5):372-383
In a companion paper (Puente et al., this issue), the capability of a deterministic fractal-multifractal (FM) approach to
faithfully and compactly describe the geometry of chloride and bromide tracers gathered at the Borden site was illustrated.
As trends in surrogate parameter space were found for successive plume contours (i.e. linear growth in coordinates by which
fractal interpolating functions pass, nearly constant rotations and fairly high scalings), this article reports usage of a
variety of prediction schemes, based on linear regressions and the aforementioned trends, in order to study the evolving plumes.
It is shown that the FM representation leads to plausible non-Gaussian plume evolutions and yields predictions that closely
approximate records for a period of time that extends even beyond one year. It is illustrated that such predicted geometries
are also consistent with predictions made via stochastic theories (i.e. Dagan, 1984). 相似文献
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The Water Framework and Habitats Directives require the evaluation of both the conservation and ecological status of macroalgae communities at water body or habitat level. However, assessments of macroalgal communities are highly time-consuming, both in terms of sampling effort and laboratory processing. These constraints have brought about their oversight in many marine monitoring programs, especially in subtidal environments. By using data from intertidal and subtidal macroalgae assemblages of Mouro Island (North coast of Spain) we wanted to identify possible cost-effective methods for monitoring this biological indicator, based on both high taxa levels and use of representative taxa. Multivariate analyses were applied using different data transformations. The results show that macroalgal communities are robust to aggregation to genus or even family level. Moreover, the outcomes show that transformation types introduce higher variation in the multivariate pattern of samples than the taxonomic level to which organisms are identified. Also, the study supports the use of representative taxa as a surrogate to overall community structure. Therefore, we conclude that a rapid-assessment by means of field evaluations, based on coverage of representative taxa, is a reliable alternative for the assessment of macroalgae status. In addition this procedure allows evaluation at a broader spatial scale (water body or habitat level) than traditional quantitative sampling procedure does. 相似文献
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Andrea Cortis Carlos E. Puente Huai-Hsien Huang Mahesh L. Maskey Bellie Sivakumar Nelson Obregón 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(6):1421-1429
In this study, we attempt to offer a solid physical basis for the deterministic fractal–multifractal (FM) approach in geophysics (Puente, Phys Let A 161:441–447, 1992; J Hydrol 187:65–80, 1996). We show how the geometric construction of derived measures, as Platonic projections of fractal interpolating functions transforming multinomial multifractal measures, naturally defines a non-trivial cascade process that may be interpreted as a particular realization of a random multiplicative cascade. In such a light, we argue that the FM approach is as “physical” as any other phenomenological approach based on Richardson’s eddies splitting, which indeed lead to well-accepted models of the intermittencies of nature, as it happens, for instance, when rainfall is interpreted as a quasi-passive tracer in a turbulent flow. Although neither a fractal interpolating function nor the specific multipliers of a random multiplicative cascade can be measured physically, we show how a fractal transformation “cuts through” plausible scenarios to produce a suitable realization that reflects specific arrangements of energies (masses) as seen in nature. This explains why the FM approach properly captures the spectrum of singularities and other statistical features of given data sets. As the FM approach faithfully encodes data sets with compression ratios typically exceeding 100:1, such a property further enhances its “physical simplicity.” We also provide a connection between the FM approach and advection–diffusion processes. 相似文献
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Aguilar-Meléndez Armando Pujades Lluis G. Barbat Alex H. Monterrubio-Velasco Marisol de la Puente Josep Lantada Nieves 《Natural Hazards》2022,110(3):1649-1691
Natural Hazards - There are personal and institutional decisions that can increase the seismic resilience of the buildings in a city. However, some of these decisions are possible if we have basic... 相似文献
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With the aim of studying the interspectific differences in the bioaccumulation of a series of elements in six species of estuarine
macrophytes, we measured the concentrations of various metals (Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), as well as C and N, in
several species of macroalgae and one species of seagrass in estuaries in northwest Spain. To facilitate the interpretation
of the results, we also determined the concentrations of the same metals in sediments. Contamination by particulate metal
did not appear to be important. The levels of Cu in the different species were generally high in comparison with those found
in similar studies; in contrast, the concentrations of Pb and Zn were relatively low. The metal concentrations showed greater
variability and a distibution that was further from normal than those of C and N. In general the highest concentrations of
elements were found inEnteromorpha spp. andZostera noltii, and the lowest occurred inUlva spp. There were several significant positive correlations among tissue concentrations of Cr, Cu, and Ni. There were also
significant correlations between tissue concentrations of N and Zn, suggesting possible synergetic effects between them. Cluster
analysis clearly revealed that the chemical composition ofZ. noltii differed from that of the macroalage. Macroalgae were not grouped according to their taxonomic position, therefore it appears
that the concentrations of the elements depended more on the ecological traits of the macroalgal species rather than on any
possible, physiological differences among different taxonomic groups. Of the species studied,Ascophyllum nodosum andEnteromorpha spp. appeared to be the best biomonitors of metal contamination. 相似文献