1,721,049 research outputs found
VISIR-I: small vessels – least-time nautical routes using wave forecasts
Full text linkA new numerical model for the on-demand computation of optimal ship routes based on sea-state forecasts has been developed. The model, named VISIR (discoVerIng Safe and effIcient Routes) is designed to support decision-makers when planning a marine voyage.
The first version of the system, VISIR-I, considers medium and small motor vessels with lengths of up to a few tens of metres and a displacement hull. The model is comprised of three components: a route optimization algorithm, a mechanical model of the ship, and a processor of the environmental fields. The optimization algorithm is based on a graph-search method with time-dependent edge weights. The algorithm is also able to compute a voluntary ship speed reduction. The ship model accounts for calm water and added wave resistance by making use of just the principal particulars of the vessel as input parameters. It also checks the optimal route for parametric roll, pure loss of stability, and surfriding/broaching-to hazard conditions. The processor of the environmental fields employs significant wave height, wave spectrum peak period, and wave direction forecast fields as input. The topological issues of coastal navigation (islands, peninsulas, narrow passages) are addressed.
Examples of VISIR-I routes in the Mediterranean Sea are provided. The optimal route may be longer in terms of miles sailed and yet it is faster and safer than the geodetic route between the same departure and arrival locations. Time savings up to 2.7 % and route lengthening up to 3.2 % are found for the case studies analysed. However, there is no upper bound for the magnitude of the changes of such route metrics, which especially in case of extreme sea states can be much greater. Route diversions result from the safety constraints and the fact that the algorithm takes into account the full temporal evolution and spatial variability of the environmental fields
Drift simulation of MH370 debris using superensemble techniques
Full text linkOn 7 March 2014 (UTC), Malaysia Airlines flight 370 vanished without a trace.
The aircraft is believed to have crashed in the southern Indian Ocean, but
despite extensive search operations the location of the wreckage is still
unknown. The first tangible evidence of the accident was discovered almost
17 months after the disappearance. On 29 July 2015, a small piece of the right
wing of the aircraft was found washed up on the island of Réunion,
approximately 4000 km from the assumed crash site. Since then a number of
other parts have been found in Mozambique, South Africa and on Rodrigues Island.
This paper presents a numerical simulation using high-resolution
oceanographic and meteorological data to predict the movement of floating
debris from the accident. Multiple model realisations are used with different
starting locations and wind drag parameters. The model realisations are
combined into a superensemble, adjusting the model weights to best represent
the discovered debris. The superensemble is then used to predict the
distribution of marine debris at various moments in time. This approach can
be easily generalised to other drift simulations where observations are
available to constrain unknown input parameters.
The distribution at the time of the accident shows that the discovered debris
most likely originated from the wide search area between 28 and
35° S. This partially overlaps with the current underwater search
area, but extends further towards the north. Results at later times show that
the most probable locations to discover washed-up debris are along the
African east coast, especially in the area around Madagascar. The debris
remaining at sea in 2016 is spread out over a wide area and its distribution
changes only slowly
Coppini and Pinardi are contributing authors
No full textnot availableEuropean Environment Agency and European Topic Centre on WaterPublished4.6. Oceanografia operativa per la valutazione dei rischi in aree marineope
Rising sea surface temperature: towards ice-free Arctic summers and a changing marine food chain Document Actions
No full textGlobal sea surface temperature is approximately 1 degree C higher now than 140 years ago, and is one of the primary physical impacts of climate change. Sea surface temperature in European seas is increasing more rapidly than in the global oceans. Projections show the temperature increases will persist throughout this century. Ice-free summers are expected in the Arctic by the end of this century, if not earlier. Already, there is evidence that many marine ecosystems in European seas are affected by rising sea temperature.European Environment Agency and European Topic Center for WaterUnpublished4.6. Oceanografia operativa per la valutazione dei rischi in aree marineope
Coppini and Pinardi are contributing authors
No full textnot availableEuropean Environment Agency and European Topic Centre on WaterPublished4.6. Oceanografia operativa per la valutazione dei rischi in aree marineope
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A box model to represent estuarine dynamics in mesoscale resolution ocean models
Full text linkRepresenting the net freshwater flux at river mouths is challenging for global and regional scale ocean modelling. Although rivers are well known to affect both the coastal and basin-wide circulation and dynamics, coarse resolution ocean models cannot resolve the estuarine dynamics and are usually forced at river outlets in a simplistic way, with climatological runoff and zero or constant salinity values. The aim of this study is to provide a more realistic representation of the estuarine water inputs to a coarse but eddy-resolving regional model. First, the river volume transport and salinity values at the outlets are modelled with three different Estuary Box Models (EBMs) for stratified estuaries: the Knudsen relations model, a published EBM, called UCONN-NCAR EBM, which parameterizes the tidal inflow and mixing inside the estuary, and a new model, called CMCC-EBM. The CMCC EBM has been conceived to represent the estuarine processes coupled to a mesoscale resolving hydrodynamic model that resolves the entering flow field at the estuary mouth and it offers a new representation of the tidal inflow and a new salinity tidal mixing parameterization via horizontal diffusive processes. The Ofanto and Po rivers flowing into the Adriatic Sea (northern part of the central Mediterranean Sea) are selected as case studies. The coupling of the eddy resolving ocean model to the CMCC EBM is found to outperform the one with the UCONN-NCAR EBM in the region of freshwater influence on the shelf area
A Structured and Unstructured grid Relocatable ocean platform for Forecasting (SURF)
No full textAbstractWe present a numerical platform named Structured and Unstructured grid Relocatable ocean platform for Forecasting (SURF). The platform is developed for short-time forecasts and is designed to be embedded in any region of the large-scale Mediterranean Forecasting System (MFS) via downscaling. We employ CTD data collected during a campaign around the Elba island to calibrate and validate SURF. The model requires an initial spin up period of a few days in order to adapt the initial interpolated fields and the subsequent solutions to the higher-resolution nested grids adopted by SURF. Through a comparison with the CTD data, we quantify the improvement obtained by SURF model compared to the coarse-resolution MFS model
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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