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In this contribution, new data concerning the distribution of native vascular flora in Italy are presented. It includes new records, confirmations, exclusions, and status changes to the Italian administrative regions. Nomenclatural and distribution updates, published elsewhere, and corrigenda are provided as Suppl. material 1.

Publisher Copyright: © This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1.

A small-scale field experiment was conducted on a U-OWC incorporated into a model of caisson breakwater at the NOEL laboratory of Reggio Calabria (Italy). The U-Oscillating Water Column (U-OWC) or REWEC (REsonant Wave Energy Converter) is a device belonging to the family of OWCs. Such a device is very innovative, being able to absorb a very percentage of incoming sea waves and to produce electrical energy via proper PTO. The focus of the paper has been the analysis of the impact wave loads acting on the modified U-OWC structure during extreme wave events. It has been observed the occurrence of both “quasi-standing wave” loads due to non-breaking waves and “impulsive wave loads” with different wave impacts exerted by a wave breaking against the U-OWC model.

This paper proposes a new approach for the calculation of extreme wind speed. Specifically, the storm approach widely employed for long-term statistics of ocean storms is reviewed and adapted for the analysis of windstorms. This approach is based on the substitution of the sequence of real event at a given site with a sequence of simplified events characterized by a kind of equivalence with the actual ones. Basing on that, analytical solution for the calculation of the return period of a storm event whose peak exceeds a given threshold is developed. The windstorm model characterizes the simplified windstorm event by means of two parameters which are the maximum average wind speed over the windstorm and a duration parameter determined by imposing that the maximum expected gust in the simplified event is the same of that in the actual one. First, an attempt is made to assimilate the peak gust to a “maximum expected gust” and to relate this quantity to the windstorm duration. Then, in order to validate the new model, a data analysis is carried out to estimate average wind speed return values with the proposed approach and results are compared with those provided by well-established peak over threshold method.

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions. Furthermore, three new combinations are proposed. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1.

The paper is focused on the formulation of an adequate criterion for associating wave storm events to the generating wind storm ones, and on the study of correlation between their characteristic parameters. In this context, the sea storm definition commonly used for storm identification from significant wave height data is adapted for wind storm, by processing wind speed data. A sensitivity analysis is proposed as function of the storm thresholds aiming at identifying optimal combination of wind speed and significant wave height thresholds allowing the association of relatively large number of events ensuring high correlation between wind and wave storm parameters. The analysis is carried out using as input data wind speeds and significant wave heights from four meteorological (buoys and anemometers) stations of the National Data Buoy Center moored off the East Coast of the United States. Results reveal that an optimal threshold combination is achieved assuming both wind speed and significant wave height threshold as 1.5 time their respective averages.

The tradition of floristic studies in Italy has made it possible to obtain a good knowledge of plant diversity both on a national and regional scale. However, the lack of knowledge for some areas, advances in plant systematics and human activities related to globalization, highlight the need for further studies aimed at improving floristic knowledge. In this paper, based on fieldwork and herbaria and literature surveys, we update the knowledge on the Italian vascular flora and analyze the floristic similarities between the administrative regions. Four taxa, all exotic, were recorded for the first time in Italy and Europe. In detail, Elaeodendron croceum, Kalanchoë blossfeldiana, and Sedum spathulifolium var. spathulifolium were found as casual aliens, while Oxalis brasiliensis was reported as historical record based on some herbarium specimens. Furthermore, Kalanchoë laxiflora was confirmed as a casual alien species for Italy and Europe. Status changes for some taxa were proposed at both national and regional levels, as well as many taxa were reported as new or confirmed at the regional level. Currently the Italian vascular flora comprises 9150 taxa of which 7547 are native (of which 1598 are Italian endemics) and 1603 are exotic at the national level. The multivariate analysis of updated floristic data on a regional scale showed a clear distribution along the latitudinal gradient, in accordance with the natural geographical location of the regions in Italy. This pattern of plants distribution was not affected by the introduction of alien species. Despite some taxonomic and methodological issues which are still open, the data obtained confirm the important role of floristic investigations in the field and in herbaria, as well as the collaborative approach among botanists, in order to improve the knowledge of the Italian and European vascular flora.

An updated checklist of the Calabrian alien vascular flora is presented. The alien flora of the Calabria region (Southern Italy) representing almost 12% of the regional flora and comprises 381 alien taxa, among which there are 370 angiosperms, 9 gymnosperms and 2 ferns. In relation to the state of spread, 35 invasive alien species (IAS) have been identified (4 of these are included in the list of Union Concern, sensu Regulation (EU) no. 1143/2014) which represent 9% of the Calabrian alien flora.In the last years the alien flora in Calabria has increased: in particular, alien species have increased over a decade from 190 to the current 381 taxa. If on the one hand this is due to new introductions, resulting from the globalization that relentlessly affects the whole planet, on the other hand it is to be linked to awareness of the problem of alien species and the increasing intensity of research in recent decades. This study would provide a baseline for further advanced studies on the management of invasive species and on the invasion ecology.

Salvia ceratophylloides (Ard.) is an endemic and rare plant species recently rediscovered as very few individuals at two different Southern Italy sites. The study of within-plant variation is fundamental to understand the plant adaptation to the local conditions, especially in rare species, and consequently to preserve plant biodiversity. Here, we reported the variation of the morpho-ecophysiological and metabolic traits between the sessile and petiolate leaf of S. ceratophylloides plants at two different sites for understanding the adaptation strategies for surviving in these habitats. The S. ceratophylloides individuals exhibited different net photosynthetic rate, maximum quantum yield, light intensity for the saturation of the photosynthetic machinery, stomatal conductance, transpiration rate, leaf area, fractal dimension, and some volatile organic compounds (VOCs) between the different leaf types. This within-plant morpho-physiological and metabolic variation was dependent on the site. These results provide empirical evidence of sharply within-plant variation of the morpho-physiological traits and VOCs profiles in S. ceratophylloides, explaining the adaptation to the local conditions.

Salvia ceratophylloides (Ard.) is an endemic, rare, threatened plant species recently rediscovered in very few individuals in two different sites of South Italy. The study of within-plant variation more than among-plant one is fundamental to understand the plant adaptation to the local conditions, especially in rare species, and consequently to preserve plant biodiversity. Here, we reported the variation of the morpho-ecophysiological and metabolic traits between the sessile and petiolate leaf of S. ceratophylloides plants in two different sites for understanding the adaptation strategies for surviving in these habitats. The S. ceratophylloides individuals exhibited different net photosynthetic rate, maximum quantum yield, light intensity for the saturation of the photosynthetic machinery, stomatal conductance, transpiration rate, leaf area, fractal dimension and some VOCs between the different leaf types. This within-plant morpho-physiological and metabolic variation was depended on the site. These results provide empirical evidence of sharply within-plant variation of the morpho-physiological traits and VOCs profiles in S. ceratophylloides which could be because of adaptation to the local conditions.

This article deals with the case study of a marina located in Roccella Jonica (Italy), where a wave energy harvester belonging to the family of U-oscillating water columns (U-OWC) is going to be installed. U-OWCs are wave energy harvesters composed of a water column exposed to the action of random sea waves and an air pocket connected to the atmosphere by a power take—off (PTO) system. In Roccella Jonica, this device is going to be embedded in a vertical breakwater expanding the main layout of the infrastructure. For ensuring the structural safety of the system, to characterize statistically its response peaks in severe environmental conditions is important. In this context, one of the main difficulties is utilizing appropriate environmental conditions representing real extreme events at the installation site. This article proposes to adopt the DNV trapezoidal storm model for representing the time history of an extreme event in conjunction with a nonlinear U-OWC model. Relevant Monte Carlo simulations show that the DNV storm model provides peak distributions that are rather close to the ones obtained by processing real storm time histories. Thus, it can be adopted for checking the performance of the system in extreme conditions.

The effects of herbivorous insects on a plant population are not always well tolerated. This is especially true if the herbivorous actions are directed toward rare plant species. Salvia ceratophylloides Ard. is a rare endemism of southern Italy. Observations of the plants in situ revealed that many of them were under severe stress and did not produce seeds. Therefore, to find out which factors affect the reproductive activity as a whole, an observational study was carried out. We found bottom-up and top-down effects on plant health and reproduction associated with herbivorous action. Squamapion elongatum (Coleoptera, Curculionoidea, Apionidae), in all monitored sites, infested plants non-uniformly but was able to threaten the health condition, flowering, and seed production of sage by digging tunnels into the sage branches (bottom-up action), and then secondarily by seed feeder Systole salvia Zerova (Hymenoptera, Eurytomidae) predating sage seeds (top-down action). Mainly, chalcid parasitoid wasps such as Trichomalus spp. (Hymenoptera, Pteromalidae), as well as Eupelmus vesicularis and E. muellneri (Hymenoptera, Eupelmidae), limited the herbivorous S. elongatum population and the seed herbivore S. salviae emerged with its parasitoid Ormyrus diffinis (Hymenoptera, Ormyridae). Overall, this study showed how ecological interactions among herbivores, their host, and their natural enemies act on this sage species in all sites investigated. Among the herbivores, mainly S. elongatum affected this rare sage species, which should be taken into consideration, especially in the formulation of biological control solutions and for improving operating practice aimed at reproducing the species. This study provides the molecular characterization of the herbivorous species involved, in order to support future projects to evaluate the intra- and interspecific genetic variability of insects, their evolutionary relationships, and phylogeny studies.

In this contribution, new data concerning the distribution of native vascular flora in Italy are presented. It includes new records, confirmations, exclusions, and status changes to the Italian administrative regions. A new combination in the genus Pilosella is proposed. Nomenclatural and distribution updates, published elsewhere, and corrigenda are provided as Suppl. material 1.

Knowledge on alien species is needed nowadays to protect natural habitats and prevent ecological damage. The presence of new alien plant species in Italy is increasing every day. Calabria, its southernmost region, is not yet well known with regard to this aspect. Thanks to fieldwork, sampling, and observing many exotic plants in Calabria, here, we report new data on 34 alien taxa. In particular, we found three new taxa for Europe (Cascabela thevetia, Ipomoea setosa subsp. pavonii, and Tecoma stans), three new for Italy (Brugmansia aurea, Narcissus &lsquo, Cotinga&rsquo, and Narcissus &lsquo, Erlicheer&rsquo, ), one new one for the Italian Peninsula (Luffa aegyptiaca), and 21 new taxa for Calabria (Allium cepa, Asparagus setaceus, Bassia scoparia, Beta vulgaris subsp. vulgaris, Bidens formosa, Casuarina equisetifolia, Cedrus atlantica, Chlorophytum comosum, Cucurbita maxima subsp. maxima, Dolichandra unguis-cati, Fagopyrum esculentum, Freesia alba, Juglans regia, Kalancho&euml, delago&euml, nsis, Passiflora caerulea, Portulaca grandiflora, Prunus armeniaca, Prunus dulcis, Solanum tuberosum, Tradescantia sillamontana, and Washingtonia filifera). Furthermore, we provide the first geolocalized record of Araujia sericifera, the confirmation of Oxalis stricta, and propose a change of status for four taxa (Cenchrus setaceus, Salpichroa origanifolia, Sesbania punicea, and Nothoscordum gracile) for Calabria. The updated knowledge on the presence of new alien species in Calabria, in Italy and in Europe could allow for the prevention of other new entries and to eliminate this potential ecological threat to natural habitats.

The paper proposes an approach for estimating the long-term statistics of random wave crests occurring over a certain space–time domain. Such a problem is relevant for a number of marine engineering applications, as classical analyses based, exclusively, on time domain approaches underestimates wave crest amplitudes associated with a given return period. The return period of a certain wave crest is derived by combining the Trapezoidal Storm (TS) Model, based on DNV GL storm profile, with the Euleric Characteristic (EC) of an excursion set concept, recently applied to the study of sea wave statistics. By computing the average EC, an explicit solution for the probability distribution of the wave crests during a sea storm can be derived by an approximation of the EC. Return period of linear wave crests is derived in the paper. The proposed solution is applied for the calculation of extreme waves during an ocean storm over a certain area. The results presented can be used as good approximation in design work of offshore installations. An extension of the proposed approach to account for nonlinearities of sea surface will be a subject of future research.

In this contribution, the conservation status assessment of three vascular plants according to IUCN categories and criteria are presented. It includes the assessment of Soldanella calabrella Kress at global level, and the regional assessment of Luzula pindica (Hausskn.) Chrtek & Křísa and Romulea variicolor Mifsud (Italy).

Despite the importance for scientific and conservation purposes, the knowledge of the Italian territory is far from exhaustive. New chorological data for 87 vascular taxa regarding the central-southern part of Italy and its two main islands (Sicilia and Sardegna) are presented. Among these taxa, Epilobium nummularifolium, Metrosideros excelsa, and Salvinia minima are recorded as casual aliens for the first time in Europe (excluding Azores and Madeira for M. excelsa), while Cyclamen balearicum and Polygala rupestris are reported for the first time and confirmed for Italian native flora, respectively. Furthermore, several taxa are new or confirmed at regional level. Finally, Lathyrus cirrhosus, Urginea fugax, and Linum tenuifolium are excluded from Italy, continental and peninsular Italy, and Sardegna, respectively.

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1.

The paper addresses the problem of deriving the nonlinear, up to the second order, crest wave height probability distribution in front of a vertical wall under the assumption of finite spectral bandwidth, finite water depth and long-crested waves. The distribution is derived by relying on the Quasi-Deterministic representation of the free surface elevation in front of the vertical wall. The theoretical results are compared against experimental data obtained by utilizing a compressive sensing algorithm for reconstructing the free surface elevation in front of the wall. The reconstruction is pursued by starting from recorded wave pressure time histories obtained by utilizing a row of pressure transducers located at various levels. The comparison shows that there is an excellent agreement between the proposed distribution and the experimental data and confirm the deviation of the crest height distribution from the Rayleigh one.

A methodology is proposed for efficient processing of sea wave field data via compressive sensing (CS), and joint time-frequency analysis via harmonic wavelets (HWs) based evolutionary power spectrum (EPS) estimation. In this regard, it is possible to record and store relatively long wave data sequences, whereas the commonly adopted in-practice assumption of stationary data is abandoned. Currently, most wave records are measured by buoys, which acquire data for a time interval representative of stationary time series. Next, following a Fourier transform processing, only few spectral parameters are stored. Thus, detailed information about localized-in-time phenomena are completely lost. Herein, it is shown that CS can be adopted for efficiently compressing and reconstructing wave data, while retaining localized information. For this purpose, CS is used in conjunction with a HW basis for processing long time series. In particular, storage capacity demands are drastically decreased as only the HW coefficients need to be saved. These are determined from a randomly-sampled record by invoking a L1/2 norm minimization procedure. The resulting reconstructed record, being longer than conventional wave time series, can no longer be regarded as stationary; thus, a HW based EPS estimate is employed for describing the joint time-frequency features of the record. Finally, the reliability of the methodology is assessed by analyzing wave field data measured at the Natural Ocean Engineering Laboratory (NOEL) of Reggio Calabria. Specifically, comparisons between original and reconstructed records demonstrate a satisfactory agreement regarding the time-histories, and the estimated EPS and relevant statistical quantities, even for up to 60% missing/removed data.

Extreme waves influence coastal engineering activities and have an immense geophysical implication. Therefore, their study, observation and extreme wave prediction are decisive for planning of mitigation measures against natural coastal hazards, ship routing, design of coastal and offshore structures. In this study, the estimates of design wave heights associated with return period of 30 and 100 years are dealt with in detail. The design wave height is estimated based on four different models to obtain a general and reliable model. Different locations are considered to perform the analysis: four sites in Indian waters (two each in Bay of Bengal and the Arabian Sea), one in the Mediterranean Sea and two in North America (one each in North Pacific Ocean and the Gulf of Maine). For the Indian water domain, European Centre for Medium-Range Weather Forecasts (ECMWF) global atmospheric reanalysis ERA-Interim wave hindcast data covering a period of 36 years have been utilized for this purpose. For the locations in Mediterranean Sea and North America, both ERA-Interim wave hindcast and buoy data are considered. The reasons for the variation in return value estimates of the ERA-Interim data and the buoy data using different estimation models are assessed in detail.

The REWEC3 (Resonant Wave Energy Converter) is a fixed oscillating water column (OWC) wave energy converter (WEC) incorporated in upright breakwaters. The device is composed by a chamber containing a water column in its lower part and an air pocket in its upper part. The air pocket is connected to the atmosphere via a duct hosting a self-rectifying air turbine. In addition, a REWEC3 includes a vertical U-shaped duct for connecting the water column to the open sea (for this reason it is known also as U-OWC). The working principle of the system is quite simple: by the action of the incident waves, the water inside the U-shaped duct is subject to a reciprocating motion, which induces alternately a compression and an expansion of the air pocket. The pressure difference between the air pocket and the atmosphere is used to drive an air turbine coupled to an off-the-shelf electrical generator connected to the grid. The main feature of the REWEC3 is the possibility of tuning the natural period of the water column in order to match a desired wave period through the size of the U-duct. The REWEC3 technology has been theoretically developed by Boccotti, later tested at the natural basin of the Natural Ocean Engineering Laboratory (NOEL, Italy), and finally proved at full scale with REWEC3 prototype built in the Port of Civitavecchia (Rome, Italy). The objective of this paper is to select and optimize a turbine/generator set of a U-shaped OWC installed in breakwaters located in the Mediterranean Sea, such as the Port of Civitavecchia, where the first prototype of REWEC3 has been realized, or the Port of Salerno or Marina delle Grazie of Roccella (Italy). The computations were performed using a time domain model based on the unsteady Bernoulli equation. Based on the time-domain model of the power plant, the following data is computed for the turbines: i) the ideal turbine diameter; ii) the generator feedback control law aiming to maximize the turbine power output for turbine coupled to the REWEC3 device for Mediterranean applications.

The paper introduces a parameterization of the DNV GL storm profile for developing an analytical model for calculations of the return period of a storm whose peak exceeds a given threshold. The DNV GL storm evolution is represented via an isosceles trapezoidal shape in which the minor base represents the storm peak duration, the major base the total storm duration and the height is half of the highest significant wave height in the actual storm. In this representation, the storm duration is not related to the storm intensity and it is fixed constant and equal to 42 hours, while the peak duration is assumed to be 6 hours. The parameterization proposed in the paper consists in expressing the peak duration as a fraction of the total storm duration allowing to investigate the effects of storm peak duration on long term estimates. The analytical solution for the return period is derived by following the classical approach of Equivalent Storm Models that is referring to the equivalent storm sequence, with the only difference that all the Trapezoidal Storm durations are identical whatever the storm intensity is. This assumption leads to significant simplification on the model development and potential employment as well. Further, a closed form solution is achieved for the return period which is also a generalization of the triangular shape. Finally, data analysis with NDBC buoys data is carried out for validating the model and elucidating analogies and differences with respect to classical Equivalent Storm approach. Results have shown that the Trapezoidal Model can be thought as a triangular one with a prudential factor on the storm peak duration which results in a reasonable overestimation of maximum expected wave height and return values.

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions of taxa in the genera Bunias, Calocedrus, Calycanthus, Celosia, Clerodendrum, Convolvulus, Crassula, Cyclamen, Datura, Dicliptera, Eragrostis, Erigeron, Gamochaeta, Gazania, Impatiens, Kolkwitzia, Leucaena, Ludwigia, Medicago, Muscari, Nigella, Oenothera, Opuntia, Paulownia, Petroselinum, Phyllostachys, Physalis, Pseudosasa, Quercus, Reynoutria, Roldana, Saccharum, Sedum, Semiarundinaria, Senecio, Sisyrinchium, Solanum, Sporobolus, Tulipa, Vachellia, Verbena, and Youngia. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1.

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, and status changes for Italy or for Italian administrative regions of taxa in the genera Abies, Actinidia, Aloe, Amaryllis, Anredera, Arctotheca, Bidens, Cardiospermum, Celosia, Commelina, Cotoneaster, Cyclamen, Eclipta, Euphorbia, Grevillea, Hedera, Hibiscus, Impatiens, Juglans, Kalanchoe, Koelreuteria, Lindernia, Melinis, Myriophyllum, Nandina, Nicotiana, Oenothera, Oxalis, Parthenocissus, Phoenix, Phyllanthus, Physalis, Plumbago, Pteris, Quercus, Setaria, Symphytum, Tagetes, and Washingtonia. Nomenclatural and distribution updates, published elsewhere are provided as Suppl. material 1.

The objective of this paper is to compare two methodologies adopted in the context of long-terms statistics: Equivalent Triangular Storm (ETS) and Peak Over Threshold (POT), applied both with the Goda model and with the Generalized Pareto Distribution. Both methodologies are currently used for conducting long-term statistics oriented to the determination of relevant input parameters adopted in the design of coastal structures. The paper proposes a dissemination of the key characteristics of the methods and elucidates the fundamental steps necessary for mechanizing the methods starting from available wave data. Then, it discusses numerical results pertaining to both Mediterranean and Ocean data. In this context, the paper focuses on the stability of the methods with respect to the (subjectively) selected storm thresholds. It shows that the ETS method is more stable than the POT. Results pertain to both omnidirectional and directional return values.

The paper proposes a new solution, in the context of equivalent storm models, for long-term statistics of ocean storms. These models are essentially based on the concept of equivalent sea which consists of substituting the actual storms at a given location with a sequence of equivalent storms, achieved from a statistical perspective. Firstly the Equivalent Triangular Storm (ETS) was proposed in which triangular storms were considered. The model was then generalized assuming a power law for a more realistic description of the storm history in time domain. The two models were developed following the same logic and assuming the equivalent storm symmetric with respect to its peak. In both cases the solution for the calculation of return period of a sea storm whose maximum significant wave height is greater than a given threshold is achieved, but only for ETSs it has a closed form and for all the others shapes it requires a numerical calculation. The main focus of the present work is to combine in a unique model the main advantages of the two previous ones, that is to obtain an optimized shape (as for EPS) and closed from solutions for the long-term statistics (as for ETS). An exponential law is introduced, taking into account asymmetry in storm profile. The long-term statistics of ocean storms is then investigated via this new Equivalent Exponential Storm (EES) model, by analyzing the effects of asymmetry between the growth and decay phases of each storm. Data from National Data buoy Center (NDBC) are processed for the new EES model validation and comparison with previous ETS and EPS. The results show that the assumption of asymmetric storm profile does not lead to significant changes of the long-term statistics, but could be very useful in other kinds of application as it enables a more realistic representation of storm history. Finally, in comparison with ETS and EPS, it has been seen that EES provides a better representation of actual storm duration.

This paper presents an approach for estimating the long-term statistics of random wave crests occurring over a certain space–time domain. Such a problem is relevant in a number of marine engineering applications, as classical analyses based, exclusively, on time domain approaches underestimate wave crest amplitudes associated with a given return period. The return period of a certain wave crest is derived by combining the Equivalent Power Storm model, used in long-term statistical analyses, with the Euler Characteristic (EC) of an excursion set concept, recently applied to the study of sea wave statistics. In this regard, the paper shows that by computing the average EC, the probability distribution of the wave crests can be derived. Specifically, an explicit solution valid for finite crest thresholds can be derived by an approximation of the EC. Thus, removing the limitation of actual solutions, which are valid only for extremely large wave crests. In addition, return period of nonlinear wave crests are derived. In this context, Forristall distribution is adopted and introduced on a heuristic basis in the EC framework. The EC approximation and the reliability of the nonlinear crest distribution is assessed against Monte Carlo data by comparing distributions of maximum wave crests both in a sea state and in a sea storm. Then, return value estimations are discussed for a number of cases.

To withstand the local wave climate, coastal structure design relies on our understanding of the wave characteristics at the structure wall and the forces they impose onto the wall. However, despite the vast number of protective structures along our coasts, detailed field observations of waves measured directly at the structure wall are virtually absent. In this study, rare observations of wave characteristics at a vertical wall are presented. Contrary to linear wave theory, results suggest that the standing waves are highly nonlinear. Waves at the wall have considerably larger kurtosis and skewness compared to the incoming wave field and the wave steepness at the wall is observed to exceed the theoretical wave steepness limit of standing waves.

The Resonant Wave Energy Converter 3 (REWEC3) is a wave energy converter belonging to the family of Oscillating Water Columns (OWCs). It comprises an oscillating water column and an air pocket connected to a turbine, as in the traditional OWCs. In addition, it has a small vertical U-shaped duct connecting the water column to the open wave field. Because of this particular geometrical configuration, it is also known as U-Oscillating Water Column (U-OWC). The first full-scale prototype was constructed in the Port of Civitavecchia (Rome, Italy), in the context of a major port enlargement. This paper shows some results of the monitoring activity pursued on one U-OWC chamber equipped with sensors measuring water and air pressures. The activity has been conducted for about 1 year. The energetic performance of the plant is investigated in the paper, via the estimation of the capture width ratio.

The Resonant Wave Energy Converter 3 (REWEC3) is a wave energy converter belonging to the family of Oscillating Water Columns (OWCs). It comprises an oscillating water column and an air pocket connected to a turbine, as for traditional OWCs. In addition, it has a small vertical U-shaped duct used for connecting the water column to the open wave field. Because of this particular geometrical configuration, it is also known as U-Oscillating Water Column (U-OWC). During the past decade, small scale field experiments and theoretical analyses proved its potential for full scale applications. Currently, a full-scale prototype has been operating in the Port of Civitavecchia (Rome, Italy), where a REWEC3 was constructed within the context of a major port enlargement. This paper shows some results of the monitoring activity on a single chamber equipped with pressure gauges. The results show some initial energetic performances of the REWEC3 in wind-generated seas.

The paper focuses on utilizing the Harmonic Wavelet Transform (HWT) for estimating the evolutionary power spectrum (EPS) of sea storms. A sea storm is considered herein as a non-stationary stochastic process with a time duration of the order of days. The storm evolution can be represented in three stages: the growth, the peak and the decay. Specifically, during growth the intensity of the wave increases with time until reaching the apex, and then decreases. The analysis is carried out by processing the time series of the free surface elevation recorded at the Natural Ocean Engineering Laboratory of Reggio Calabria, Italy. A peculiarity of the NOEL lab is that a local wind from NNW often generates sea states consisting of pure wind waves that represent a small scale model, in Froude similarity, of ocean storms (www.noel.unirc.it). The main focus of the paper is, first, to acquire a joint time-frequency representation of the storm via estimating the associated EPS, and second, to explore the variability in time of the spectrum and of the dominant frequencies of the storm. The EPS is estimated by utilizing a non-stationary record of the sea surface elevation during a storm recorded at NOEL lab. Further, in this paper, the standard representation of sea storms is also considered. That is, the non-stationary process is represented as a sequence of stationary processes (sea states or buoy records), each of them characterized by an intensity defined by a significant wave height Hs and by a duration Δt. During the time interval Δt the sea surface elevation is considered stationary and the frequency spectrum may be computed via the Fast Fourier Transform (FFT). Results obtained following this procedure, which can be considered essentially as a brute-force application of the short-time FT, are compared with those obtained via a HWT based joint time-frequency analysis.

The paper suggests a generalized approach to the analysis of second-order three-dimensional random wave fields that can represent either ocean waves in an undisturbed field or standing ocean waves. A nonlinear stochastic family is introduced that has a linear stationary Gaussian random contribution and a second-order correction exact in a Stokes expansion. This family can describe the nonlinear mechanics of a random wave field. Subsequently, in the considered random ocean field, the nonlinear mechanics of wave groups can be investigated conditional to the occurrence of a very high wave. The free-surface displacement and velocity potential may be obtained, as well as the nonlinear wave velocity and acceleration, for both the stochastic family and the very high wave groups. The results are of interest for the analysis of nonlinear wave kinematics when extreme surface wave events occur and thus for Morison′s wave forces on slender structures.

This paper proposes a parameterization of the Det Norske Veritas and Germanischer Lloyd (DNV GL) storm profile for the development of analytical solution for the calculation of the associated return period. This solution allows the possibility of calculating the design wave for marine structures by means of a very simple approach. The basic concept is to substitute the sequence of actual storms at a given site with a sequence of trapezoidal storms (TS) defined on the basis of the DNV GL storm temporal evolution and derive analytically the return period referring to the TSs sequence. The DNV GL storm is represented by a trapezium which may be totally defined by means of three parameters: the trapezium height related to the storm intensity, and its minor and major bases, which represent two durations Dp, D* pertaining to the maximum significant wave height Hsmax and to 50% of Hsmax, respectively. It is assumed that the parameters Dp, D* are uncorrelated to the storm intensity and are the same for all the storms. With this assumption, the return period is obtained in a closed form as a function of the ratio n between Dp and D*, D* itself, and of the exceedance probability distribution of significant wave height. The model is validated by comparison with Equivalent Triangular Storm (ETS) model by processing buoys data at four locations representative of different wave climates: Haltenbanken in North Sea, Alghero in Mediterranean Sea, stations 41001 and 46006 in Atlantic and Pacific Oceans, respectively. Results reveal that although its significant simplicity, the TS model provides reliable estimate of return values which are in agreement with those achieved by ETS model. Further, the employment of TS model with the values of parameters n and D* corresponding to the DNV GL profile is suitable for any location.

The paper deals with the analysis of severe storms in the central Mediterranean Sea and in the US coasts of the Atlantic and Pacific Ocean. Firstly, we introduce a model for the representation of the sea storms by means of two parameters: the former is given by the maximum value of significant wave height in the actual storm and defines the storm intensity, the latter gives the storm duration. The analysis considers buoy data with different sampling Δt between two consecu- tive records, which varies in the range 0.5 - 6 hours. The sensitivity analysis of the modelled sea storm with the varia- tion of Δt shows as the structure of storms is strongly modified with large values of Δt of order of 3 - 6 hours: both the intensity and the duration may change significantly. The results are of interest to investigate the extreme events in the storms obtained with WAve Model, starting from meteorological data, where the value of Δt of 6 hours is widely applied. The conclusion is that structure of severe storms should be represented with continuous data, with Δt = 0.5 hours; a good representation is also obtained with Δt = 1 hour. The errors with increasing values of Δt are investigated.

The design of an energy harvester involves achieving the two following objectives: to install a safe structure with a reasonable safety margin; and to install an effective device which is able to capture energy in a variety of environmental conditions. In this context, the long-term modelling of the environmental variables plays a crucial role. In the context of wave energy harvesters, the occurrence of sea storms is a critical element in the design process. Indeed, its identification is required for determining extreme loads as well as controlled de-activations of the device for preserving the mechanical components into the device. Considering these issues, the paper proposes an analysis of the wave climate oriented to the determination of the downtime and of the energy losses. Specifically, the paper provides expressions: for calculating the average deactivation time of a wave energy device, given that it must be deactivated if the significant wave height is larger than a certain threshold; and for calculating the energy “lost” (as it is not absorbed by the device) during a storm in which the maximum wave height is larger than the mentioned threshold. The paper shows that closed-form expressions can be obtained by relying on the Equivalent Triangular Storm (ETS) model and that the adequacy of the estimations improves for larger values of the significant wave height threshold.

This paper deals with the implementation of a control algorithm for a turbine equipped into a U-Oscillating water column (U-OWC) plant. The open literature has largely ignored the problem of coupling the U-OWC behaviour to the turbine behaviour with the objective of maximizing the energy harvesting. Therefore, this paper has the objective of assessing the reliability of a Maximum Power Point Tracking (MPPT) algorithm. The paper uses a numerical algorithm for estimating the energy produced by a U-OWC in real seas. In this regard, the computations rely on long time domain analyses that allow testing a variety of environmental conditions. The MPPT is proved adequate for controlling the turbine behavior in conjunction with U-OWCs. In this context, it is shown that a reference parameter, used for determining the reference rotational speed, can be the significant wave height.

The problem of maximizing the performances of a U-OWC wave energy converter in a variet of environmental conditions is investigated. Specifically, the paper compares two control strategies coupling the U-OWC – PTO system. Two approaches are discussed. The first relies on the tracking of the Maximum Power Points of the system, and empirical relations between the optimal PTO performances and the energy content of the incident sea state are estimated. Secondly, an analytical formulation linking the operational conditions of the turbine to the instantaneous air pressure inside the pneumatic chamber is identified. Results show that a sea state-based controller works better than a wave-to wave fast-acting control.

The objective of this paper is to provide a synthetic tool for determining expeditiously the wave climate conditions in several areas of the Mediterranean Sea. In the open literature, several authors have already conducted this specific analysis also for the area under examination in this paper. However, the need of discussing aspects strictly related to the design of wave energy harvesters is still relevant. Therefore, considering the variety of devices and the amount of information needed for conducting both an energy-wise optimization and a structural reliability assessment, a holistic view on the topic is provided. Specifically, the paper elucidates the theoretical aspects involved in the estimation of wave energy statistics and in the calculation of relevant return values. Next, it provides synthetic data representing the mean wave power and the return value of extreme events in several coastal areas of the Mediterranean Sea. In this regard, the paper complements information available in the open literature by discussing the influence of the directional pattern of the sea states in the determination of sea state statistics as well as in the design of a wave energy harvester. © 2014 Elsevier Ltd.

The paper deals with the directional analysis of severe storms in some European locations, in the Atlantic Ocean and North Sea. The analysis is carried out by considering significant wave height and wave direction time series, from the HIPOCAS project database. At each considered location, all storms in the data set are identified. Then, for each storm, variability of direction during sea states is investigated. The results of this analysis show how direction during storms varies within well-defined sectors identified from the main directions from which the strongest storms occur plus or minus a certain angle Δϑ, and from one or more secondary sectors. The variation of direction during storms is evaluated in terms of standard deviation of direction, either by considering all sea states during storm, or only sea states during the part of the storm above a fixed threshold h of significant wave height. The results show that standard deviation of direction decreases as the threshold h increases and it is due to the fact that variability of direction near the storm peak is smaller than in the full storm.Copyright © 2014 by ASME

In the last decades, the research has directed its efforts and resources paper is to investigate towards the possibility to incorporate wave energy converters, into the traditional maritime breakwaters to combine classical use with new opportunities and developments (for example, the Green Ports). Since the nineties, the OWC (Oscillating Water Column) plants were developed at full scale to produce electrical power from ocean waves. For instance, a new plant was built in Mutriku (Spain) recently. A new kind of OWC caisson, named U-OWC or REWEC3, which has the advantage to obtain an impressive natural resonance without any device for phase control, has been patented by Boccotti [1]. This new U-OWC device gives performances better than those of a conventional OWC either with small wind waves or with high waves [2,3,4]. The properties of the REWEC3 have been verified with two small-scale field experiments carried out in the natural ocean engineering laboratory NOEL of Reggio Calabria off the eastern coast of the Sicily Channel [5–7]. The aim of the present two sites along Italian coasts for possible installations of REWEC3 devices: i) the port of Civitavecchia (Rome, Italy)in the Tyrrhenian sea; ii) the port of Pantelleria, in the Sicily Channel.

This work proposes an analysis of storms in Pacific and Atlantic Ocean, which is carried out by applying the Boccotti’s Equivalent Triangular Storm (ETS) model. The ETS model represents any actual storm by means of two parameters. The former gives the storm intensity, which is equal to the maximum significant wave height during the actual storm; the latter represents the storm duration and it is such that the maximum expected wave height is the same in the actual storm and in the equivalent triangular storm. Data from buoys of the NOAA-NDBC (National Data Buoy Center, USA) are used in the applications, by considering different sampling Δt between two consecutive records, which varies between 1 and 6 hours. The sensitivity of the ETS model with the variation of Δt is investigated for the long-term modeling of severe storms. The results show that the structure of storms is strongly modified as Δt increases: both the intensity and the duration may change significantly. The effects of this results for long term statistics are investigated by means of the return period R(Hs > h) of a storm in which the maximum significant wave height exceeds the threshold h, which is evaluated by using data with different sampling Δt between two consecutive records. Finally for different values of the return period R, the return value of significant wave height and the mean persistence Dm(h), giving the mean time during which the significant wave height is greater than fixed threshold (in the storms where the threshold is exceeded), are calculated.