Destabilization of the thermohaline circulation by transient changes in the hydrological cycle     

Valerio Lucarini  Sandro Calmanti  Vincenzo Artale 《Climate Dynamics》2005,24(2-3):253-262

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Exploring the thermal cycle of the Northern North Sea area using a 3-D circulation model: the example of PROVESS NNS station     

Georg Umgiesser  Patrick J. Luyten  Sandro Carniel   《Journal of Sea Research》2002,48(4):266

Within the framework of activities of the EC funded Project ‘Processes of Vertical Exchange in Shelf Seas’ (PROVESS), the seasonal thermal behaviour during 1998 at a station in the North Sea has been investigated using COHERENS, a three-dimensional fully non-linear hydrodynamic model. Extensive hydrographic measurements were carried out at the Northern North Sea (NNS) station, located at (59°20′N, 1°E). The collected data are used to validate the model results, showing an acceptable agreement between modelled temperatures and those obtained from CTDs and moored thermistors. This is valid both for surface and bottom temperatures, while the mixed layer thickness appears to be underestimated. A series of 3-D runs, testing different turbulence schemes, an internal wave mixing (IWM) parameterisation and the sensitivity to an increase of the surface stress, have been performed with the aim of assessing the relative importance of the advective and mixing processes. The model comparisons mostly evidenced differences in the behaviour of the bottom layer temperature during the last part of the year, which may be due to advection processes. The adoption of an internal wave mixing parameterisation, though managing to reproduce a deeper thermocline, overestimates the mixing around the period of the thermocline breakdown. The run adopting a wind stress increased by 50% provides a better agreement between observed and modelled thermocline. This applies also for surface velocities when compared to Acoustic Doppler Current Profiler (ADCP) measurements, while the bottom ones appear slightly underestimated only in the U-component. The Northern North Sea site appears to be located close to a gyre induced by thermal fronts. Comparisons with nearby wind data measured by an oil rig and by the ships operating in the area seem to confirm that the wind forcing values adopted during the integration are underestimated.  相似文献   

On the influence of etch pits in the overall dissolution rate of apatite basal sections     

Igor Alencar  Sandro Guedes  Rosane Palissari  Julio C. Hadler 《Physics and Chemistry of Minerals》2015,42(8):629-640

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Modeling of transient groundwater flow,pollutant transport,and biodegradation in an aquifer with large hydraulic head variations     

Sandro Rinaldi  Sihem Louati  Hocine Bendjoudi  Ghislain de Marsily 《Hydrogeology Journal》2014,22(4):943-956

Industrially sourced dense non-aqueous phase liquids (DNAPLs) contaminated an alluvial aquifer in France decades ago. The location(s) and nature of the pollution source zone(s) were unknown, and the dissolved concentrations of volatile organic compounds in the monitoring wells varied greatly with time. The aquifer was in hydraulic equilibrium with an artificial canal whose water level was highly variable (up to 5 m). These variations propagated into the aquifer, causing changes in the groundwater flow direction; a transient numerical model of flow and solute transport showed that they correlate with the concentration variations because the changes in the flow direction resulted in the contaminant plume shifting. The transient hydrogeological numerical model was built, taking into account solvent biodegradation with first-order chain, since biodegradation has a significant influence on the pollutant concentration evolution. The model parameterization confirms the position of the source zones among the potential troughs in the bedrock where DNAPLs could have accumulated. The groundwater model was successfully calibrated to reproduce the observed concentration variations over several years and allowed a rapid validation of the hypotheses on the functioning of the polluted system.  相似文献   

A homogeneous sample of sub-damped Lyman α systems – II. Statistical, kinematic and chemical properties     

Céline Péroux †  Miroslava Dessauges-Zavadsky  Sandro D'Odorico  Tae-Sun Kim  Richard G. McMahon 《Monthly notices of the Royal Astronomical Society》2003,345(2):480-496

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Validation of turbulence closure parameterisations for stably stratified flows using the PROVESS turbulence measurements in the North Sea     

Patrick J. Luyten  Sandro Carniel  Georg Umgiesser 《Journal of Sea Research》2002,47(3-4)

A number of parameterisations for the simulation of mixing processes in the thermocline are compared and tested against the microstructure data of the PROVESS campaigns, conducted in the northern part of the North Sea during the autumn of 1998. The transport term in the turbulent kinetic energy equation is parameterised via the introduction of a third stability function S_k for turbulent energy diffusion. The formulations are compared with a simpler scheme based upon limiting conditions for turbulence variables. Improved results are obtained with a new form of S_k. The best agreement is, however, found with the simpler limiting scheme. This is explained in terms of a turbulence length scale theory for stably stratified turbulence. In agreement with previous laboratory and ocean data it is found that the ratios of the Thorpe and Kolmogorov scales to the Ozmidov length scale approach critical limiting values in the thermocline. The first of these conditions is satisfied when limiting conditions are implemented into the scheme, providing the necessary minimum value for the dissipation rate, whereas the schemes without limiting conditions fail to produce this critical ratio. The basic reason for this failure is that the Thorpe scale is overestimated, which is shown to be connected to an even larger overprediction of the dissipation rate of temperature variance. To investigate the impact of non-resolved advective processes and salinity stratification on the turbulence predictions, additional numerical experiments were conducted using a simple scheme for data assimilation. The best agreement is found again with the limiting scheme, which is able to make reasonable predictions for the dissipation rate without knowing the detailed shape of the mean stratification profile. It is shown that advective transport due to tidally and wind-driven motions has a non-negligible impact on vertical mixing. This is seen in the data and the models by periodic enhancements of turbulent mixing inside the thermocline.  相似文献   

Extensive characterization of Italian accelerometric stations from single-station ambient-vibration measurements     

Rodolfo Puglia  Dario Albarello  Antonella Gorini  Lucia Luzi  Sandro Marcucci  Francesca Pacor 《Bulletin of Earthquake Engineering》2011,9(6):1821-1838

This paper describes the analyses of the single-station ambient-vibration measurements performed on the Italian accelerometric network to detect site resonance phenomena potentially affecting earthquake recordings. The use of low cost, high quality microtremor measurement can be helpful to discriminate among soil classes, since several classification schemes based on resonance frequencies were proposed in the last decades. Operatively, in the framework of the Italian Strong Motion Database project (DPC-INGV 2007–2009 S4; ), soil resonance frequencies have been evaluated from more than 200 ambient vibration measurements in correspondence of accelerometric stations included in ITACA (). The noise recordings have been analyzed using the same numerical protocol in order to standardize the results. Particular attention has been paid to evaluate the quality of measurements and to develop an on-purpose mathematical tool to automatically estimate the peaks in the horizontal-to-vertical spectral ratio (HVSR) curve. The reliability of the resonance frequencies from HVSR has been tested by comparing estimates provided by independent methods (modeling or earthquake recordings). The test confirmed the reliability of the microtremor HVSR for assessing the resonance frequencies of the examined sites.  相似文献   

Use of biomarkers indices in a sediment core to evaluate potential pollution sources in a subtropical reservoir in Brazil   总被引：1，自引：0，他引：1  

Juan Sánez  Sandro Froehner  Filipe Falcão 《Chemie der Erde / Geochemistry》2013

The presence of PAHs, n-alkanes, pristane, and phytanes in core sediment from the Vossoroca reservoir (Parana, southern Brazil) was investigated. The total concentration of the 16 PAHs varied from 15.5 to 1646 μg kg⁻¹. Naphthalene was present in all layers (3.34–74.0 μg kg⁻¹). The most abundant and dominant n-alkanes were n-C₁₅ and n-C₃₆, with average concentrations of 198.1 ± 46.8 and 522.9 ± 167.7 μg kg⁻¹, respectively. Lighter n-alkanes were distributed more evenly through the layers and showed less variation, specially n-C₉, n-C₁₂, and n-C₁₈, with average concentrations of 14.6 ± 3.0, 31.6 ± 1.9, and 95.0 ± 5.2 μg kg⁻¹, respectively; heavier n-alkanes were more unevenly distributed.  相似文献   

Erratum to: Future projections of the surface heat and water budgets of the Mediterranean Sea in an ensemble of coupled atmosphere–ocean regional climate models     

C. Dubois  S. Somot  S. Calmanti  A. Carillo  M. Déqué  A. Dell’Aquila  A. Elizalde  S. Gualdi  D. Jacob  B. L’Hévéder  L. Li  P. Oddo  G. Sannino  E. Scoccimarro  F. Sevault 《Climate Dynamics》2012,39(12):3125-3125

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The Italian strong motion network   总被引：2，自引：2，他引：0  

Antonella Gorini  Mario Nicoletti  Paolo Marsan  Riccardo Bianconi  Rita De Nardis  Luisa Filippi  Sandro Marcucci  Franco Palma  Elisa Zambonelli 《Bulletin of Earthquake Engineering》2010,8(5):1075-1090

The Italian Strong Motion Network is a permanent monitoring system run by the Italian national emergency management department (Dipartimento della Protezione Civile, DPC). The network is known as RAN (Rete Accelerometrica Nazionale). An extensive project for updating and improving the technology of RAN instruments as well as the number of recording points was performed in the last 10 years. A wide site selection survey was carried out from eastern Sicily along the Italian peninsula, covering high seismic risk areas. The recording station density and the choice of high-quality digital strong motion instruments ensure reliability of the RAN network in the long-term. At the end of 2008, the free field sites selection and instruments installation, planned in the project, were quite completed. In planning and drawing the new RAN, special attention has been devoted to the robustness of the transmission systems, and to the distribution of new stations in order to ensure plenty of data during a seismic emergency. We spent special care both in the estimation of the RAN site responses and in the diffusion of the strong motion data. In order to better identify damaged earthquake areas, improved ground motion parameters need to be set. Such parameters will also assist future progress for engineering seismic design techniques as well as disaster mitigation.  相似文献