579 research outputs found
Sea-level variability in the Mediterranean Sea from altimetry and tide gauges
No full textSea-level variability in the Mediterranean Sea was investigated by means of in-situ (tide-gauge) and satellite altimetry data over a period spanning two decades (from 1993 to 2012). The paper details the sea-level variations during this time period retrieved from the two data sets. Mean sea-level (MSL) estimates obtained from tide-gauge data showed root mean square differences (RMSDs) in the order of 40–50 % of the variance of the MSL signal estimated from satellite altimetry data, with a dependency on the number and quality of the in-situ data considered. Considering the individual time-series, the results showed that coastal tide-gauge and satellite sea-level signals are comparable, with RMSDs that range between 2.5 and 5 cm and correlation coefficients up to the order of 0.8. A coherence analysis and power spectra comparison showed that two signals have a very similar energetic content at semi-annual temporal scales and below, while a phase drift was observed at higher frequencies. Positive sea-level linear trends for the analysis period were estimated for both the mean sea-level and the coastal stations. From 1993 to 2012, the mean sea-level trend (2.44 ± 0.5 mm year- 1) was found to be affected by the positive anomalies of 2010 and 2011, which were observed in all the cases analysed and were mainly distributed in the eastern part of the basin. Ensemble empirical mode decomposition showed that these events were related to the processes that have dominant periodicities of ∼ 10 years, and positive residual sea-level trend were generally observed in both data-sets. In terms of mean sea-level trends, a significant positive sea-level trend (> 95 %) in the Mediterranean Sea was found on the basis of at least 15 years of data. © 2016, The Author(s)
Low carbon intensity routes via ocean currents and waves
No full textThe VISIR ship routing model is augmented with the capability to employ, on top of waves, also ocean currents for optimising vessel routes. A case study for a cargo vessel sailing between the Chesapeake Bay (USA) and Lisbon (Portugal) is considered. The seasonal variability of the route pattern is visualised, with the major ocean boundary current impacting in a specific way, depending on the prevailing sailing direction. In the approximation of CO2 emissions proportional to sailing time, the impact on the Energy Efficiency Operational Indicator (EEOI) proposed by the International Maritime Organization is also computed. The seasonal variability of EEOI demonstrates, for a given parametrisation of vessel energy loss in waves, potential savings in the 3-12% range, with respect to navigation along a least-distance route, and in the 1-5% range, with respect to navigation along a least-time route which neglects the role of ocean currents. These figures refer to monthly mean values, while individual routes may exhibit EEOI savings up to 20% and 6%, respectively
A Prototype of Ship Routing Decision Support System for an Operational Oceanographic Service.
No full textA prototype for an operational ship routing
Decision Support System using time dependent
meteo‐oceanographic fields is presented.
The control variable is ship course, which is modified using a directional resolution of less than 27 degrees. The shortest path is recovered using a modified Dijkstra’s algorithm.
Safety restrictions for avoiding surfriding and parametric rolling according to the guidelines of the International Maritime Organization (IMO) areimplemented.
Numerical experiments tailored on a medium‐size vessel are presented and perspectives of development of the system are outline
Tecniche decisionali e l. n. 87/1953: un rapporto (sempre più) conflittuale
No full textLo scritto riproduce un intervento svolto nell'ambito del Convegno annuale del Gruppo di Pisa, tenutosi a Como il 26 e 27 maggio del 2023, e finalizzato a discutere dell’attualità di alcune norme contenute nella l. n. 87/1953, a settant’anni dalla loro entrata in vigore, in tema di tecniche decisorie (in particola-re: pronunce manipolative a rime "possibili" e sentenze di accoglimento ad efficacia esclusivamente pro futuro) che vengono utilizzate dalla Corte costituzionale nei giudizi sulle legg
The halting effect of baroclinicity in vortex merging
No full textStudies the quasigeostrophic merging dynamics of axisymmetric baroclinic vortices to understand how baroclinicity affects merging rates and the development of the nonlinear cascade of enstrophy. The initial vortices are taken to simulate closely the horizontal and vertical structure of Gulf Stream rings. A quasigeostrophic model is set with a horizontal resolution of 9 km and 6 vertical levels to resolve the mean stratification of the Gulf Stream region. The results show that the baroclinic merging is slower than the purely barotropic process. -from Author
Risk Assessment of operational oil releases in the Adriatic Sea, in the Tyrrhenian Sea, Ligurian Sea and in the Sicily Strait
No full textOil slicks caused by oil tanker accidents compose a major source of hydrocarbon pollution for the marine and coastal environment and can jeopardize its functional integrity. However, the deliberate discharge of oil and oily residues associated with routine tanker operations (bilges residues, tank oil sediments) and from illegal activities, highlights a far-reaching source of pollution perhaps more important than the one caused by accidents (EEA, 2002). The Adriatic Sea with an annual oil transport of 70 MT (million tons) is probably highly affected by operational pollution. Estimates give about 15 000 mt (metric tons) of such residues deliberately discharged every year denoting a major hazard for the marine and coastal environment of Adriatic region (Bilardo et al, 2004)).
Risk mapping appears as the most appropriate way to approach the management of oil pollution in marine areas and in order to assess the ecosystem health state. Modern risk mapping should, tackle the intrinsic variability of the marine environment and the lack of knowledge regarding the cause-effects relationships on vulnerability of resources, in other words should consider the inherent uncertainty of the system. Thus risk management requires products that are time-dependent and that allow the continuous assessment of the system space and time variability. Modern operational oceanography gives the appropriate time and space resolution for the ocean hydrodynamics (Pinardi et al., 2003) so that time dependent risk mapping can be developed.PublishedMarseille, France4.6. Oceanografia operativa per la valutazione dei rischi in aree marineope
Linking 1D coastal ocean modeling to environmental management: an ensemble approach.
No full textThe use of a one-dimensional interdisciplinary numerical model of the coastal ocean as a tool contributing to the formulation of ecosystem-based management (EBM) is explored. The focus is on the definition of an experimental design based on ensemble simulations, integrating variability linked to scenarios (characterised by changes in the system forcing) and to the concurrent variation of selected, and poorly constrained, model parameters. The modelling system used was previously specifically designed for the use in “data-rich” areas, so that horizontal dynamics can be resolved by a diagnostic approach and external inputs can be parameterised by nudging schemes properly calibrated. Ensembles determined by changes in the simulated environmental (physical and biogeochemical) dynamics, under joint forcing and parameterisation variations, highlight the uncertainties associated to the application of specific scenarios
that are relevant to EBM, providing an assessment of the reliability of the predicted changes. The work has been carried out by implementing the coupled modelling system BFM-POM1D in an area of Gulf of Trieste (northern Adriatic Sea), considered homogeneous from the point of view of hydrological properties, and forcing it by changing climatic (warming) and anthropogenic (reduction of the land-based nutrient input) pressure. Model parameters affected by considerable uncertainties (due to the lack of relevant observations) were varied jointly with the scenarios
of change. The resulting large set of ensemble simulations provided a general estimation of the model uncertaintiesrelated to the joint variation of pressures and model parameters.
The information of the model result variability aimed at conveying efficiently and comprehensibly the information on the uncertainties/reliability of the model results to non-technical EBM planners and stakeholders, in order to have the model-based information effectively contributing to EBM
Risk Assessment of operational oil releases in the Adriatic Sea, in the Tyrrhenian Sea, Ligurian Sea and in the Sicily Strait
No full textOil slicks caused by oil tanker accidents compose a major source of hydrocarbon pollution for the marine and coastal environment and can jeopardize its functional integrity. However, the deliberate discharge of oil and oily residues associated with routine tanker operations (bilges residues, tank oil sediments) and from illegal activities, highlights a far-reaching source of pollution perhaps more important than the one caused by accidents (EEA, 2002). The Adriatic Sea with an annual oil transport of 70 MT (million tons) is probably highly affected by operational pollution. Estimates give about 15 000 mt (metric tons) of such residues deliberately discharged every year denoting a major hazard for the marine and coastal environment of Adriatic region (Bilardo et al, 2004)).
Risk mapping appears as the most appropriate way to approach the management of oil pollution in marine areas and in order to assess the ecosystem health state. Modern risk mapping should, tackle the intrinsic variability of the marine environment and the lack of knowledge regarding the cause-effects relationships on vulnerability of resources, in other words should consider the inherent uncertainty of the system. Thus risk management requires products that are time-dependent and that allow the continuous assessment of the system space and time variability. Modern operational oceanography gives the appropriate time and space resolution for the ocean hydrodynamics (Pinardi et al., 2003) so that time dependent risk mapping can be developed.PublishedMarseille, France4.6. Oceanografia operativa per la valutazione dei rischi in aree marineope
MEDSLIK-II, a Lagrangian marine surface oil spill model for short-term forecasting – Part 1: Theory
No full textThe processes of transport, diffusion and transformation of surface oil in
seawater can be simulated using a Lagrangian model formalism coupled with
Eulerian circulation models. This paper describes the formalism and the
conceptual assumptions of a Lagrangian marine surface oil slick numerical model and
rewrites the constitutive equations in a modern mathematical framework. The
Lagrangian numerical representation of the oil slick requires three different
state variables: the slick, the particle and the structural state variables.
Transformation processes (evaporation, spreading, dispersion and coastal
adhesion) act on the slick state variables, while particle variables are
used to model the transport and diffusion processes. The slick and particle
variables are recombined together to compute the oil concentration in water,
a structural state variable. The mathematical and numerical formulation of
oil transport, diffusion and transformation processes described in this
paper, together with the many simplifying hypothesis and parameterizations,
form the basis of a new, open source Lagrangian surface oil spill model,
the so-called MEDSLIK-II, based on its precursor MEDSLIK (Lardner et al., 1998, 2006; Zodiatis et al., 2008a).
Part 2 of this paper describes the applications of
the model to oil spill simulations that allow the validation of the model
results and the study of the sensitivity of the simulated oil slick to
different model numerical parameterizations
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