bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling local winds over the Salento peninsula
Authors: Mangia Cristina , Martano Paolo , Miglietta Mario Marcello , Morabito Angela , Tanzarella Annalisa 
Published: October 2004

AbstractA three‐day mesoscale numerical simulation has been performed over the narrow Salento peninsula (south‐eastern Italy) during summer conditions characterised by weak synoptic forcing. These atmospheric conditions favour the development of complex sea‐breeze systems and convergence zones on the peninsula. The aim of this work is to investigate the ability of an atmospheric mesoscale model to reproduce the surface fields of meteorological variables in the presence of local‐scale forcing and breeze circulations, which are fundamental in applications such as air pollution modelling and nowcasting.The modelled fields have been compared with available surface measurements and sodar data. Results indicate that the model can simulate the general mean wind field in a realistic way. The diurnal evolution of the wind is well reproduced and the maximum deviations mostly occur during the night, being associated with calm conditions.Statistical analysis indicates that the typical mean bias is found to be about 1 m s−1 for hourly averaged wind speed, less than 20° for wind direction and about 1°C for temperature. The root mean square error (rmse) varies from 1 to 3 m s−1 for wind speed, from 50° to 70° for wind direction, and is about 2.4°C for temperature. All the values of the numerical indexes are within ranges which are characteristic of those found for other state‐of‐the‐art models applied to similar cases studies.Despite a good overall agreement between predictions and observations, some discrepancies were found in the individual profiles due both to the limited spatial representation of the local details and to the complex wind field which makes the space–time matching between the model and the observations quite critical.The structures of the thermal mixed layer and the breeze convergence zone are similar to numerical studies relative to more idealised conditions. Copyright © 2004 Royal Meteorological Society
Applications of radar‐based nowcasting techniques for mesoscale weather forecasting in Hong Kong
Authors: Li P. W. , Lai Edwin S. T. 
Published: October 2004

AbstractOperational forecasting of mesoscale weather systems in Hong Kong is supported by an automated nowcasting system called SWIRLS (Short‐range Warning of Intense Rainstorms in Localised Systems). SWIRLS is based on the extrapolation of radar echoes using the TREC (Tracking Radar Echoes by Correlation) technique. With a suitable choice of pixel array size on the radar reflectivity maps, the TREC vectors derived can be used to monitor and extrapolate echo motion right across the mesoscale spectrum, from individual convective cells, to supercells and clusters, and to groups of rainbands or squall lines.On the basis of TREC, quantitative precipitation forecast (QPF) algorithms have been developed to produce high resolution forecast rainfall distribution maps over the local area. These maps provide useful objective guidance for forecasters to assess the likely rain scenario in the next few hours and to facilitate decision‐making in operating the Rainstorm Warning System. This review, however, will focus on other aspects of TREC applications and some side benefits for operational mesoscale forecasting in Hong Kong. First, extension of the TREC technique to group tracking of echoes (GTrack) have enabled forecasters to make qualitative educated guesses of the likelihood of prolonged heavy rain or the potential of enhanced storm development. Secondly, extension of the QPF algorithms to a forecast range of 3 hours, supplemented by real‐time accumulated rainfall data from a high density raingauge network, has enabled forecasters to provide reliable advice and guidance to geotechnical engineers for landslip risk assessment. Thirdly, rain‐related applications aside, TREC vectors are also ingested into a data analysis system LAPS (Local Analysis and Prediction System) adapted from Forecast Systems Laboratory (FSL) of NOAA. Through the assimilation of TREC vectors and other wind observations, a three‐dimensional wind structure of tropical cyclones can be generated in near real‐time for forecasters' reference in assessing landfall impact. Copyright © 2004 Royal Meteorological Society
Pollutant transport schemes integrated in a numerical weather prediction model: model description and verification results
Authors: Chenevez Jérôme , Baklanov Alexander , Havskov Sørensen Jens 
Published: October 2004

AbstractRegional air pollution models are usually off‐line coupled with numerical weather prediction models. The present study, however, focuses on on‐line coupled modelling, for which the air pollution model is an integral part of the meteorological model. To this purpose, simulations of the first European Tracer Experiment (ETEX), which supplies the best suited verification data for dispersion modelling of a passive tracer, have been performed using versions of the Danish Meteorological Institute High Resolution Limited‐Area Model (DMI‐HIRLAM). Simulation results have been compared with observed values as well as with results from other models.The operational version of DMI‐HIRLAM using well‐known basic advection schemes has been tested, showing the need for improvements for air pollution purposes. The fourth‐order Bott algorithm for advection has thus been implemented in the semi‐Lagrangian version of DMI‐HIRLAM. Due to its practically perfect mass conservation properties and its low computational cost, this method turns out to be efficient for simulations of transport of pollutants in the atmosphere. This represents a first effort towards a fully integrated air pollution model, e.g. for forecasting purposes. Copyright © 2004 Royal Meteorological Society
Design as materials research: building a cathedral to last 500 years
Authors: Roberts Nicholas W. 
Published: October 2004

‘A city seventy miles square but rarely seventy years deep apart from a small downtown not yet two centuries old and a few other pockets of ancientry, Los Angeles is instant architecture on an instant townscape.’ (Banham, 1971)Two opposing attitudes shape the built environment of North America: the myth of transience and the myth of permanence.
Size matters: the value of small populations for wintering waterbirds
Authors: Jackson Sarah F. , Kershaw Melanie , Gaston Kevin J. 
Published: October 2004

AbstractProtecting systematically selected areas of land is a major step towards biodiversity conservation worldwide. Indeed, the identification and designation of protected areas more often than not forms a core component of both national and international conservation policies. In this paper we provide an overview of those Special Protection Areas and Ramsar Sites that have been classified in Great Britain as of 1998/99 for a selection of wintering waterbird species, using bird count data from the Wetland Bird Survey. The performance of this network of sites is remarkable, particularly in comparison with published analyses of networks elsewhere in the world. Nevertheless, the current site‐based approach, whilst having the great benefit of simplicity, is deliberately biased towards aggregating species at the expense of the more dispersed distribution species. To ensure that the network continues successfully to protect nationally and internationally important waterbird populations, efforts now need to concentrate on the derivation of species‐specific representation targets and, in particular, the ways in which these can be incorporated into the site selection process. Although these analyses concern the performance of protected areas for waterbirds in Great Britain, the results have wide‐ranging importance for conservation planning in general and the design of protected area networks.
The importance of species interactions in conservation: the endangered European bitterling Rhodeus sericeus and its freshwater mussel hosts
Authors: Mills Suzanne C. , Reynolds John D. 
Published: October 2004

AbstractSpecies conservation may be complicated in symbiotic interactions. Sub‐lethal impacts of human activities on one species may be lethal to other species on which they depend. We investigated the impact of two aspects of eutrophication – changes in phytoplankton and oxygen levels – on the interaction between a freshwater fish that is endangered in several countries, the European bitterling, Rhodeus sericeus, and the unionid mussel hosts that they require for spawning. Reduced concentrations of algae and oxygen each led to a greater proportion of bitterling embryos being ejected prematurely from the mussel hosts. Reduced algal concentrations also led to reductions in mussel ventilation rates and to mussels spending less time with their valves open. Bitterling mortality may have been due to three causes: direct effects of environmental conditions on embryonic survival, active expulsion by mussels when stressed and through responses by mussels that created internal conditions that bitterling embryos could not survive. Our study shows that the sub‐lethal effects of pollution on one species can have lethal effects on another species with which it interacts. Such interactions need to be considered in conservation programmes.
Spatial structure and the control of invasive alien species
Authors: Travis Justin M. J. , Park Kirsty J. 
Published: October 2004

AbstractInvasive alien species pose a significant threat to biodiversity worldwide and many eradication programmes are now underway in an effort to reduce the impact they may have on native species and ecosystems. The spatial structure of such invasive species populations is likely to have important implications for designing effective control strategies. Here, a simple source–sink population model is used to address the following question: if a population of an invasive alien species is source–sink in nature, what is the best way of dividing limited resources for its control? Results from this model indicate that allocation of resources solely to the source population does not always result in the most effective control strategy. The most efficient control measure is determined by the relative strengths (net gains and losses) of the source and sink populations and, crucially, the nature of dispersal between them. We present a case study for the control of an invasive species illustrating the use of these types of model.
Flower visitors and pollination in the Oriental (Indomalayan) Region
Authors: Corlett Richard T. 
Published: October 2004

ABSTRACTCurrent knowledge of flower visitors and pollination in the Oriental Region is summarised. Much less is known about pollination than seed dispersal and the coverage of habitats and taxa in the region is very uneven. The available evidence suggests that pollination in lowland forests is dominated by highly social bees (mainly Trigona and Apis species), with beetles probably the next most important group, followed by other bees and flies. In comparison with the better‐studied Neotropics, large solitary bees, moths, Lepidoptera and vertebrates are relatively less important. These differences are greatest in the canopy of the lowland dipterocarp forests of Southeast Asia, where they probably reflect the unique temporal pattern of floral resource availability resulting from‘general flowering’at supra‐annual intervals. Apis bees (but not Trigona species) are also important in most montane, subtropical and non‐forest habitats. Apart from the figs (Ficus spp.), there are few well‐documented examples of plant species visited by a single potential pollinator and most plant‐pollinator relationships in the region appear to be relatively generalised. The small sizes of most pollinators and the absence of direct human exploitation probably make pollination mutualisms less vulnerable to failure as a result of human impacts than dispersal mutualisms, but more subtle impacts, as a result of altered gene flows, are likely to be widespread. On current evidence, pollination systems in the Oriental Region do not require any specific conservation action, but this review reinforces arguments for making the preservation (or restoration) of habitat connectivity the major focus of Oriental conservation.
Social influences on mammalian circadian rhythms: animal and human studies
Authors: Mistlberger Ralph E. , Skene Debra J. 
Published: October 2004

ABSTRACTWhile light is considered the dominant stimulus for entraining (synchronizing) mammalian circadian rhythms to local environmental time, social stimuli are also widely cited as‘zeitgebers’(time‐cues). This review critically assesses the evidence for social influences on mammalian circadian rhythms, and possible mechanisms of action. Social stimuli may affect circadian behavioural programmes by regulating the phase and period of circadian clocks (i.e. a zeitgeber action, either direct or by conditioning to photic zeitgebers), by influencing daily patterns of light exposure or modulating light input to the clock, or by associative learning processes that utilize circadian time as a discriminative or conditioned stimulus. There is good evidence that social stimuli can act as zeitgebers. In several species maternal signals are the primary zeitgeber in utero and prior to weaning. Adults of some species can also be phase shifted or entrained by single or periodic social interactions, but these effects are often weak, and appear to be mediated by social stimulation of arousal. There is no strong evidence yet for sensory‐specific nonphotic inputs to the clock. The circadian phase‐dependence of clock resetting to social stimuli or arousal (the‘nonphotic’phase response curve, PRC), where known, is distinct from that to light and similar in diurnal and nocturnal animals. There is some evidence that induction of arousal can modulate light input to the clock, but no studies yet of whether social stimuli can shift the clock by conditioning to photic cues, or be incorporated into the circadian programme by associative learning. In humans, social zeitgebers appear weak by comparison with light. In temporal isolation or under weak light‐dark cycles, humans may ignore social cues and free‐run independently, although cases of mutual synchrony among two or more group‐housed individuals have been reported. Social cues may affect circadian timing by controlling sleep‐wake states, but the phase of entrainment observed to fixed sleep‐wake schedules in dim light is consistent with photic mediation (scheduled variations in behavioural state necessarily create daily light‐dark cycles unless subjects are housed in constant dark or have no eyes). By contrast, discrete exercise sessions can induce phase shifts consistent with the nonphotic PRC observed in animal studies. The best evidence for social entrainment in humans is from a few totally blind subjects who synchronize to the 24 h day, or to near‐24 h sleep‐wake schedules under laboratory conditions. However, the critical entraining stimuli have not yet been identified, and there are no reported cases yet of social entrainment in bilaterally enucleated blind subjects. The role of social zeitgebers in mammalian behavioural ecology, their mechanisms of action, and their utility for manipulating circadian rhythms in humans, remains to be more fully elaborated.
Comparison of molecular mechanisms mediating cell contact phenomena in model developmental systems: an exploration of universality
Authors: Bowers‐Morrow Vivienne M. , Ali Sinan O. , Williams Keith L. 
Published: October 2004

ABSTRACTAre there universal molecular mechanisms associated with cell contact phenomena during metazoan ontogenesis? Comparison of adhesion systems in disparate model systems indicates the existence of unifying principles.Requirements for multicellularity are (a) the construction of three‐dimensional structures involving a crucial balance between adhesiveness and motility; and (b) the establishment of integration at molecular, cellular, tissue, and organismal levels of organization. Mechanisms for (i) cell–cell and cell–substrate adhesion, (if) cell movement, (Hi) cell‐cell communication, (iv) cellular responses, (v) regulation of these processes, and (vi) their integration with patterning, growth, and other developmental processes are all crucial to metazoan development, and must have been present for the emergence and radiation of Metazoa. The principal unifying themes of this review are the dynamics and regulation of cell contact phenomena.Our knowledge of the dynamic molecular mechanisms underlying cell contact phenomena remains fragmentary. Here we examine the molecular bases of cell contact phenomena using extant model developmental systems (representing a wide range of phyla) including the simplest i.e. sponges, and the eukaryotic protist Dictyostelium discoideum, the more complex Drosophila melanogaster, and vertebrate systems. We discuss cell contact phenomena in a broad developmental context.The molecular language of cell contact phenomena is complex; it involves a plethora of structurally and functionally diverse molecules, and diverse modes of intermolecular interactions mediated by protein and/or carbohydrate moieties. Reasons for this are presumably the necessity for a high degree of specificity of inter‐molecular interactions, the requirement for a multitude of different signals, and the apparent requirement for an increasingly large repertoire of cell contact molecules in more complex developmental systems, such as the developing vertebrate nervous system. However, comparison of molecular models for dynamic adhesion in sponges and in vertebrates indicates that, in spite of significant differences in the details of the way specific cell–cell adhesion is mediated, similar principles are involved in the mechanisms employed by members of disparate phyla. Universal requirements are likely to include (a) rapidly reversible intermolecular interactions; (b) low‐affinity intermolecular interactions with fast on–off rates; (c) the compounding of multiple intermolecular interactions; (d) associated regulatory signalling systems. The apparent widespread employment of molecular mechanisms involving cadherin‐like cell adhesion molecules suggests the fundamental importance of cadherin function during development, particularly in epithelial morphogenesis, cell sorting, and segregation of cells.
Individual colour patches as multicomponent signals
Authors: Grether Gregory F. , Kolluru Gita R. , Nersissian Karen 
Published: October 2004

ABSTRACTColour patches are complex traits, the components of which may evolve independently through a variety of mechanisms. Although usually treated as simple, two‐dimensional characters and classified as either structural or pigmentary, in reality colour patches are complicated, three‐dimensional structures that often contain multiple pigment types and structural features. The basic dermal chromatophore unit of fishes, reptiles and amphibians consists of three contiguous cell layers. Xanthophores and erythrophores in the outermost layer contain carotenoid and pteridine pigments that absorb short‐wave light; iridophores in the middle layer contain crystalline platelets that reflect light back through the xanthophores; and melanophores in the basal layer contain melanins that absorb light across the spectrum. Changes in any one component of a chromatophore unit can drastically alter the reflectance spectrum produced, and for any given adaptive outcome (e.g. an increase in visibility), there may be multiple biochemical or cellular routes that evolution could take, allowing for divergent responses by different populations or species to similar selection regimes. All of the mechanisms of signal evolution that previously have been applied to single ornaments (including whole colour patches) could potentially be applied to the individual components of colour patches. To reach a complete understanding of colour patch evolution, however, it may be necessary to take an explicitly multi‐trait approach. Here, we review multiple trait evolution theory and the basic mechanisms of colour production in fishes, reptiles and amphibians, and use a combination of computer simulations and empirical examples to show how multiple trait evolution theory can be applied to the components of single colour patches. This integrative perspective on animal colouration opens up a host of new questions and hypotheses. We offer specific, testable functional hypotheses for the most common pigmentary (carotenoid, pteridine and melanin) and structural components of vertebrate colour patches.
Vegetation dynamics – simulating responses to climatic change
Authors: Woodward F. I. , Lomas M. R. 
Published: October 2004

ABSTRACTA modelling approach to simulating vegetation dynamics is described, incorporating critical processes of carbon sequestration, growth, mortality and distribution. The model has been developed to investigate the responses of vegetation to environmental change, at time scales from days to centuries and from the local to the global scale. The model is outlined and subsequent tests, against independent data sources, are relatively successful, from the small scale to the global scale. Tests against eddy covariance observations of carbon exchange by vegetation indicated significant differences between measured and simulated net ecosystem production (NEP). NEP is the net of large fluxes due to gross primary production and respiration, which are not directly measured and so there is some uncertainty in explaining differences between observations and simulations. In addition it was noted that closer agreement of fluxes was achieved for natural, or long‐lived managed vegetation than for recently managed vegetation. The discrepancies appear to be most closely related to respiratory carbon losses from the soil, but this area needs further exploration. The differences do not scale up to the global scale, where simulated and measured global net biome production were similar, indicating that fluxes measured at the managed observed sites are not typical globally.The model (the Sheffield Dynamic Global Vegetation Model, SDGVM) has been applied to contemporary vegetation dynamics and indicates a significant CO2 fertilisation effect on the sequestration of atmospheric CO2. The terrestrial carbon sink for the 20th century is simulated to be widespread between latitudes 40° S and 65° N. but is greatest between 10° S and 6° N, excluding the effects of human deforestation. The mean maximum sink capacity over the 20th century is small, at 25 gCm‐2 year‐1, or approximately 1% of gross primary production.Simulations of vegetation dynamics under a scenario of future global warming indicate a gradual decline in the terrestrial carbon sink, with the capacity to absorb human emissions of CO2 being reduced from 20% in 2000 to approximately 2% between 2075 and 2100. The responses of carbon sequestration and vegetation structure and distribution to stabilisation of climate and CO2 may extend for up to 50 years after stabilisation has occurred.