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121.
A hydrodynamic model of the Bay of Toulon has been developed for use as a post-accident radionuclide dispersion simulation tool. Located in a Mediterranean urban area, the Bay of Toulon is separated into two basins by a 1.4-km long seawall. The Little Bay is semi-enclosed and connected to the Large Bay by a fairway channel. This channel is the site of significant water mass exchange as a result of both wind-driven currents and bathymetry. It is therefore a focal point for marine contamination. As part of the model calibration and validation process, the first step consisted of studying the water mass exchange between the two basins. An Acoustic Doppler Current Profiler was moored in the channel for 1 year. The present study analyses in situ data to determine the current intensity and direction, and also to better understand the vertical current profile, which is highly correlated with meteorological forcing. Comparisons of model-generated and measured data are presented, and various atmospheric forcing datasets are used to enhance computed results. It appears that accurate meteorological forcing data is needed to enhance the accuracy of the hydrodynamic model. This channel is an important location for water mass renewal in the Bay of Toulon, and model results are used to quantify these exchanges. The mean calculated annual water exchange time is approximately 3.4 days. However, this duration is strongly wind dependent and shortens during windy winter months. It ranges from 1.5 days during strong wind periods to 7.5 days during calm weather. Residence time values calculated through tracer dispersion modelling after release at the back of the Little Bay are found to be comparable to the mean exchange time values, especially for windy conditions. 相似文献
122.
Innovative Germicidal UV and Photocatalytic System Dedicated to Aircraft Cabin Eliminates Volatile Organic Compounds and Pathogenic Micro‐Organisms 下载免费PDF全文
123.
Platinum-group element (PGE) abundances in mantle rocks are generally considered to result from a late meteorite addition to the early Earth, post-dating the core separation event. As such, PGEs are key tracers for the Earth accretion history. For decades, the PGEs systematics of undepleted mantle peridotites has been used to constrain the composition of meteorite impactors involved in the late veneer material. Despite multiple evidence of considerable modifications by partial melting, harzburgites from the Sumail ophiolite (Oman) display a mean PGE composition very akin to recently refined estimates for the Primitive Upper Mantle (PUM) of the Earth. These rocks document a resetting of the PUM signature by percolating basaltic melts, which precipitated Pd-enriched Cu–Ni sulphides within a strongly Pd-depleted residual harzburgitic protolith. Such a resetting casts doubt on both the reliability of any PUM estimates and relevance of the PUM concept itself, at least for PGEs. 相似文献
124.
Abstract Uptake rates of ammonium (NH4 + ), nitrate (NO3 ? ), and urea by three subgroups of phytoplankton (< 200, < 20, < 2 μm) off Westland, were measured using 15 N tracer techniques in midwinter 1988, after a recent upwelling. For all size fractions at surface irradiance (I100), nitrogen (N) was taken up primarily as NO3 ?. This accounted for 67–85% of total N uptake (SρN), whereas at 40 and 7% of surface irradiance, the regenerated N (NH4 + ) and urea) made up 31–72% of SρN. Depth profile experiments for all three size components showed that uptake of NO3 ? was most light‐sensitive, followed by that of NH4 + and urea. The irradiance and nutrient availability plot indicated that light was substantially more important than the nutrient concentrations in controlling the assimilation of N by microplankton (20–200 μm). Nano‐ (2–20 μm) and picoplankton (< 2 μm) however, were not as sensitive to either light or nutrient concentrations. High winds and the resulting deep mixing, combined with offshore and alongshore advection in the midwinter, were suggested to be the major cause of the low biomass and N productivity. 相似文献
125.
Determination of the rate and total amount of limestone pavement surface lowering is a critical issue in developing models of regional landscape change in limestone terrain. Erratic‐capped pedestals have frequently been used for this purpose but problems concerning definition and measurement of pedestal height, and the absence of a secure timeframe for erratic emplacement, have resulted in conflicting interpretations. We have used cosmogenic (36Cl) to establish the emplacement age of erratic boulders and the total amount of pavement surface lowering at sites in northwest England. Since erratic emplacement at 17.9 ka the limestone pavement has been lowered by 22–45 cm (average: 33 ± 10 cm), assuming lowering was continuous. Although indicating some spatial heterogeneity, the results contrast with earlier reported values based on the measurement of pedestal heights and inferred age for deglaciation. We consider that changes in climate and the character and duration of regolith covers to have been important influences in promoting surface lowering. It is argued that nivation (chemical and mechanical snow‐related processes) associated with several cool/cold periods is likely to have played an important role in surface lowering. Complicating factors associated with surface lowering (thickness and longevity of snow and regolith covers) are identified but as yet cannot be quantified. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
126.
127.
Bruno Castelle B. G. Ruessink Philippe Bonneton Vincent Marieu Nicolas Bruneau Timothy D. Price 《地球表面变化过程与地形》2010,35(7):771-781
Double sandbar systems are common morphological features along sandy, wave‐dominated, micro‐ to meso‐tidal coastlines. In the companion paper, we demonstrated how various alongshore inner‐bar rip‐channel patterns can develop through morphological coupling to an alongshore‐variable outer bar. The simulated coupling patterns are, however, scarcely observed in the field. Instead, inner‐bar rip channels more often possess remarkably smaller and more variable alongshore length scales, suggesting that coupling mechanisms do not play a substantial role in the overall double‐sandbar dynamics. Here we use a numerical model to show that the relative importance of self‐organization and morphological coupling changes in favour of the latter with an increase in waterdepth variability along the outer‐bar crest. Furthermore, we find that the typical alongshore variability in inner‐bar rip‐channel scale is indicative of a mixture of self‐organization and morphological coupling rather than self‐organization alone. Morphological coupling may thus be more important to understanding and predicting the evolution of inner‐bar rip channels than previously envisaged. Copyright © 2010 John Wiley and Sons, Ltd. 相似文献
128.
Vladimir Kossobokov Jean-Louis Le Mouël Vincent Courtillot 《Journal of Atmospheric and Solar》2010,72(7-8):595-606
We study the effect of solar variability on temperatures recorded in three European stations with the longest gapless series available (Prague, Bologna and Uccle). Following a pattern recognition approach, we partition daily temperature “indices” (minimum, maximum and range) in two separate classes with respect to the level of solar activity (high H vs low L 11 year cycles). Using the two-sample Kolmogorov–Smirnov statistics, multiple shuffles of data, and other partitions, we demonstrate that the separation between the probability distribution functions of H and L temperatures is statistically significant and robust. We find that average annual variations for the H and L classes display common and site-specific patterns. For practically all series considered, differences between graphs of annual change for the two classes H and L are large (~1 °C). Solar activity accounts, at least in part, for the multi-decadal variations in temperature observed at these European sites in the past two centuries. 相似文献
129.
130.
Richard Comblen Sébastien Blaise Vincent Legat Jean-François Remacle Eric Deleersnijder Jonathan Lambrechts 《Ocean Dynamics》2010,60(6):1395-1414
We describe the time discretization of a three-dimensional baroclinic finite element model for the hydrostatic Boussinesq
equations based upon a discontinuous Galerkin finite element method. On one hand, the time marching algorithm is based on
an efficient mode splitting. To ensure compatibility between the barotropic and baroclinic modes in the splitting algorithm,
we introduce Lagrange multipliers in the discrete formulation. On the other hand, the use of implicit–explicit Runge–Kutta
methods enables us to treat stiff linear operators implicitly, while the rest of the nonlinear dynamics is treated explicitly.
By way of illustration, the time evolution of the flow over a tall isolated seamount on the sphere is simulated. The seamount
height is 90% of the mean sea depth. Vortex shedding and Taylor caps are observed. The simulation compares well with results
published by other authors. 相似文献