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101.
102.
If a parameter field to be calibrated consists of more than one statistical population, usually not only the parameter values are uncertain, but the spatial distributions of the populations are uncertain as well. In this study, we demonstrate the potential of the multimodal calibration method we proposed recently for the calibration of such fields, as applied to real-world ground water models with several additional stochastic parameter fields. Our method enables the calibration of the spatial distribution of the statistical populations, as well as their spatially correlated parameterization, while honoring the complete prior geostatistical definition of the multimodal parameter field. We illustrate the implications of the method in terms of the reliability of the posterior model by comparing its performance to that of a "conventional" calibration approach in which the positions of the statistical populations are not allowed to change. Information from synthetic calibration runs is used to show how ignoring the uncertainty involved in the positions of the statistical populations not only denies the modeler the opportunity to use the measurement information to improve these positions but also unduly influences the posterior intrapopulation distributions, causes unjustified adjustments to the cocalibrated parameter fields, and results in poorer observation reproduction. The proposed multimodal calibration allows a more complete treatment of the relevant uncertainties, which prevents the abovementioned adverse effects and renders a more trustworthy posterior model. 相似文献
103.
Epiphytic diatoms as flood indicators 总被引:1,自引:0,他引:1
Johan A. Wiklund Natalie Bozinovski Roland I. Hall Brent B. Wolfe 《Journal of Paleolimnology》2010,44(1):25-42
The hydroecology of floodplain lakes is strongly regulated by flood events. The threat of climate warming and increasing human
activities requires development of scientific methods to quantify changes in the frequency of short-lived flood events, because
they remain difficult to identify using conventional paleolimnological and monitoring approaches. We developed an approach
to detect floods in sediment records by comparing the abundance and composition of epiphytic diatom communities in flooded
and non-flooded ponds of the Peace-Athabasca Delta (PAD), Canada, that grew on submerged macrophytes (Potamogeton zosteriformis, P.
perfoliatus) and an artificial substrate (polypropylene sheets) during the open-water season of 2005. Analysis of similarity tests showed
that epiphytic diatom community composition differs significantly between flooded and non-flooded ponds. After accounting
for the “pond effect,” paired comparisons of the three substrates determined that variation in community composition between
the artificial substrate and macrophytes was similar to that between the macrophyte taxa. Similarity percentage analysis identified
diatom taxa that discriminate between flooded and non-flooded ponds. The relative abundance of ‘strong flood indicator taxa’
was used to construct an event-scale flood record spanning the past 180 years using analyses of sedimentary diatom assemblages
from a closed-drainage pond (PAD 5). Results were verified by close agreement with an independent paleoflood record from a
nearby flood-prone oxbow pond (PAD 54) and historical records. Comparison of epiphytic diatoms in flooded and non-flooded
lakes in this study provides a promising approach to detect changes in flood frequency, and may have applications for reconstructing
other pulse-type disturbances such as hurricanes and pollutant spills. 相似文献
104.
Khadija Semhi Osman A. E. Abdalla Salah Al Khirbash Tabisam Khan Salim Asaidi Sardar Farooq 《Arabian Journal of Geosciences》2009,2(2):143-150
Groundwater samples from six wells and various species of plants from soils developed on ophiolites were collected from an arid area (AlKhod area, Oman) and analyzed for trace elements including rare earth elements (REEs). The distribution patterns of REEs in plants indicated an enrichment in middle REEs (MREEs?=?Sm to Dy) and heavy REEs (HREEs?=?Ho to Lu), when they are normalized to the REE composition of the Post Archean Australian Shale (PAAS), with a significant negative anomaly in Ce and a positive anomaly in Eu. Compared to Oman ophiolites, the REEs in different species of plants are depleted in Ce and enriched in MREEs and slightly enriched in light REE (LREE?=?from La to Nd). Relative to PAAS, the distribution of REEs in groundwaters revealed similar patterns to the REE distribution in plants. The distribution patterns of REEs in plants relative to those in waters are nearly flat. These patterns suggest that the transfer of REEs from soil solutions to the groundwaters in Oman occurs without any significant fractionation. 相似文献
105.
Abstract Industrial land development has become a key feature of urbanization in Greater Jakarta, one of the largest metropolitan areas in Southeast Asia. Following Suharto's market-oriented policy measures in the late 1980s, private developers have dominated the land development projects in Greater Jakarta. The article investigates the extent to which these private industrial centers have effectively reduced the domination of Jakarta in shaping the entire metropolitan structure. The analysis indicates that major suburban industrial centers have captured most of the manufacturing employment that has dispersed from Jakarta. The industrial centers have now increasingly specialized and diversified. It is likely that a polycentric metropolitan structure will emerge in the future. 相似文献
106.
Miguel Angel de Lucas Pardo Marieke Bakker Thijs van Kessel Francesco Cozzoli Johan Christian Winterwerp 《Ocean Dynamics》2013,63(9-10):1137-1150
The Markermeer is a large and shallow man-made freshwater lake in the Netherlands, characterized by its high turbidity. As part of a study aiming to mitigate this high turbidity, we studied the water–bed exchange processes of the lake’s muddy bed. The upper centimeter’s–decimeter’s of the lake bed sediments mainly consists of soft anoxic mud. Recent measurements have proved the existence of a thin oxic layer on top of this soft anoxic mud. This oxic layer, which is much easier to be eroded than the anoxic mud, is believed to be related with Markermeer’s high-turbidity levels. Our hypothesis is that the thin oxic layer develops from the anoxic mud, enhanced by bioturbation. Actually, we will demonstrate that it is the bioturbated state of the bed that increases its erodability, and not the oxidation state of the sediments. In particular, we will refer to bioturbation caused by meiobenthic fauna. The objective of this study is therefore to determine the influence of the development of the thin oxic layer on the water–bed exchange processes, as well as to establish the role of bioturbation on those processes. This is done by quantifying the erosion rate as a function of bed shear stresses, and at different stages of the development of the oxic layer. Our experiments show that bioturbation increases the rate at which Markermeer sediments are eroded by almost an order of magnitude. The short-term fine sediment dynamics in Markermeer are found to be driven by the complex and highly dynamic interactions between physics, chemistry, and biology. Finally, the long-term fine sediment dynamics are driven by the erosion of the historical deposits in the lake’s bed, which is only possible after bioturbation, and which leads to an increase of the stock of sediments in the lake’s muddy bed. 相似文献
107.
Iqbal Zafar Shahid Shamsuddin Ahmed Kamal Wang Xiaojun Ismail Tarmizi Gabriel Hamza Farooq 《Theoretical and Applied Climatology》2022,148(3-4):1429-1446
Theoretical and Applied Climatology - Satellite-based precipitation (SBP) is emerging as a reliable source for high-resolution rainfall estimates over the globe. However, uncertainty in SBP is... 相似文献
108.
Coastal flood risks and seasonal tourism: analysing the effects of tourism dynamics on casualty calculations 总被引:1,自引:1,他引:0
Wim Kellens Tijs Neutens Pieter Deckers Johan Reyns Philippe De Maeyer 《Natural Hazards》2012,60(3):1211-1229
Since coastal tourism is one of the fastest growing sectors of tourism industry, coastal areas have become increasingly vulnerable
in the case of flooding. While in recent years a number of different methods have been put forward to map coastal flood risks,
the implications of tourism dynamics for the assessment of human casualties has remained largely overlooked in these models.
This chapter examines to what extent the ignorance of (residential) coastal tourism may bias the calculations of human casualties.
To this end, a case study has been conducted on the Belgian coast. Both the dynamic nature of coastal tourism and the behaviour
of residential tourists in storm surge scenarios are considered. The results of this study show that including tourism dynamics
in flood risk management is justified and appropriate, depending on the tourist attractiveness of the flood-prone area and
its temporal fluctuations. 相似文献
109.
The heavily eutrophicated Limfjorden (Denmark) provides a good illustration of the value of long-term monitoring, especially
if this is combined with an experimental, interdisciplinary research approach. Here, we first give a short overview of the
environmental status of Limfjorden, including the historical development of nutrient overloading and subsequent oxygen depletion
in near-bottom water, and how the annual landings of edible bottom-dwelling fish species (plaice, flounder, eel and others)
caught in Limfjorden have decreased from about 2,500 t in the early 1920s to only about 20 t in recent years where the fish
have been replaced by an increasing number of especially the moon jellyfish, Aurelia aurita, which mainly preys on zooplankton. Next, we evaluate the ecological consequences of the present high number of jellyfish,
based on data from recent years’ research on the abundance of jellyfish, their population dynamics and predation impact. In
Limfjorden, the benthic polyp stage of A. aurita ensures a large number of small ephyrae in the early spring and subsequently a large population of adult medusae that control
the zooplankton during summer and autumn. The holopelagic invasive ctenophore Mnemiopsis leidyi, which was observed in Limfjorden for the first time in 2007, is a second carnivore adding additional predation pressure
of the indigenous A. aurita so that copepods and other mesozooplankton organisms may be virtually absent, as observed in 2008 and 2009 where ciliates
made up a substantial part of the zooplankton biomass. Marine environmental management programmes should be aware of the increasing
importance of both indigenous and new invasive jellyfish species that may show mass occurrence in especially eutrophicated
and over-fished areas. 相似文献
110.
This study assesses the origin and pollution of trace metals in surface soils in a region with contrasting land uses (urban
vs. rural). Principal component analysis (PCA) reveals that Cr and Ni are predominantly of geogenic origin. These two trace
metals are also the only ones with statistically significant correlations with soil particle size and organic matter content.
Copper, Pb and Zn, and possibly Hg, are of anthropogenic origin, but their concentrations rarely reach levels described as
strongly polluted by pollution indexes. The concentrations of these anthropogenic trace metals are statistically not different
in urban and rural areas, except for Pb that is higher in the urban area. This general lack of a difference between the two
land uses indicates that the influence of this small urban area on trace metal concentrations in soils is minor. Lead and
Zn have the most, but still a modest number, of strongly polluted sites, mainly in an industrial part of the city. GIS analysis
shows that, based on the pollution load index (PLI), overall concentrations of trace metals also reach their highest levels
in that industrial area. These observations indicate that the influence of industry on trace metal pollution in soil exceeds
that of other urban activities in the region. Local background concentrations were found to be very different from general
crustal background concentrations. This demonstrates the importance of the careful selection of a background type in studies
like this. 相似文献