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Casas-Prat M.,Center Internacional dInvestigacio Dels Recursos Costaners | Sierra J.P.,University of Barcelona
Natural Hazards and Earth System Science | Year: 2010

In the context of wave climate variability, long-term alterations in the wave storminess pattern of the Catalan coast (northwestern Mediterranean Sea) are analysed in terms of wave energy content and wave direction, on the basis of wave hindcast data (from 44-year time series). In general, no significant temporal trends are found for annual mean and maximum energy. However, the same analysis carried out separately for different wave directions reveals a remarkable increase in the storm energy of events from the south, which is partly due to a rise in the annual percentage of such storms. A case study of Tarragona Port (on the southern Catalan coast) highlights the importance of including changes in wave direction in the study of potential impacts of climate change. In particular, an increase in the frequency of storms from the south leads to greater agitation inside the Port. © 2010 Author(s).


Sierra J.P.,Polytechnic University of Catalonia | Sierra J.P.,Center Internacional dInvestigacio dels Recursos Costaners | Mosso C.,Polytechnic University of Catalonia | Mosso C.,Center Internacional dInvestigacio dels Recursos Costaners | And 2 more authors.
Renewable Energy | Year: 2014

Menorca (Balearic Islands) only covers 2% of its electricity needs with renewable energy sources, which is far below the European Union's objective of obtaining 20% of its energy from these sources. This study analyses the island's wave energy resources using a 17-year series of data obtained from numerical modeling (forecast). The spatial distribution of wave power is analyzed using data from 12 points around the island. The obtained resources (average wave power, around 8.9kW/m; average annual wave energy, about 78MWh/m) are relatively modest but among the largest found in the Mediterranean Sea. The northeast and east of the island are the most productive areas. Considerable seasonal variability is found, with winters being rather energetic and summers quite mild. The power matrices of three wave energy converters (WECs) are considered to assess the average power output at all of the points. Four places are identified as the best candidates for WEC deployment, with non-negligible productivity that can be exploited to supply energy to small villages. © 2014 Elsevier Ltd.


Casas-Prat M.,Polytechnic University of Catalonia | Casas-Prat M.,Center Internacional dInvestigacio dels Recursos Costaners | Wang X.L.,Environment Canada | Sierra J.P.,Polytechnic University of Catalonia | Sierra J.P.,Center Internacional dInvestigacio dels Recursos Costaners
Ocean Modelling | Year: 2014

This study proposes a computationally inexpensive statistical method for modeling ocean wave heights, focusing particularly on modeling wave heights in near-shore areas. A multiple linear regression is used to predict significant wave heights (H s) using predictors derived from the sea level pressure (SLP) field, including the use of squared SLP gradients to represent geostrophic winds. One time step lagged H s is also included as a predictor, which could be interpreted as the first order derivative in the spectral energy balance governing equation. Further, based on the frequency/directional dispersion theory of waves, the swell component is accounted for by using a set of selected principal components derived from the squared SLP gradient vectors (including magnitudes and directions). The effect of non-Gaussian (non-negative) variables is also assessed by applying two types of transformation to the data.The proposed method is evaluated and shown to have good skills for the study area (Catalan coast). This method can be used to project possible future wave climate change for use in coastal impact assessment studies. It is used in this study to project the wave climate for the study area that corresponds to 5 sets of regional climate model (RCM) atmospheric projections, which were made by different RCMs forced by the same global circulation model (GCM), or by the same RCM forced by two GCMs. For the season analyzed (winter), the results show that the uncertainty due to using different GCMs to drive the same RCM is greater than that due to using different RCMs driven by the same GCM. © 2013 The Authors.


Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio dels Recursos Costaners | Aretxabaleta A.L.,U.S. Geological Survey | Espino M.,Polytechnic University of Catalonia | And 2 more authors.
Journal of Geophysical Research: Oceans | Year: 2012

We examine the circulation over the inner-shelf of the Catalan Sea using observations of currents obtained from three Acoustic Doppler Current Profilers (two at 24 m and one at 50 m) during March-April 2011. The along-shelf current fluctuations during that period are mainly controlled by local wind stress on short time scales and by remote pressure gradients on synoptic time scales. Different forcing mechanisms are involved in the along-shelf momentum balance. During storm conditions, wind stress, sea level gradients and the nonlinear terms dominate the balance. During weak wind conditions, the momentum balance is controlled by the pressure gradient, while during periods of moderate wind in the presence of considerable stratification, the balance is established between the Coriolis and wind stress terms. Vertical variations of velocity are affected by the strong observed density gradient. The increased vertical shear is accompanied by the development of stratified conditions due to local heating when the wind is not able to counteract (and break) stratification. The occasional influence of the Besòs River plume is observed in time scales of hours to days in a limited area in near the city of Barcelona. The area affected by the plume depends on the vertical extent of the fresher layer, the fast river discharge peak, and the relaxation of cross-shore velocities after northeast storm events. This contribution provides a first interpretation of the inner-shelf dynamics in the Catalan Sea. © 2012. American Geophysical Union. All Rights Reserved.


Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio Dels Recursos Costaners | Aretxabaleta A.L.,Integrated Statistics | Espino M.,Polytechnic University of Catalonia | Espino M.,Center Internacional dInvestigacio Dels Recursos Costaners
Journal of Geophysical Research C: Oceans | Year: 2015

Cross and along-shelf winds drive cross-shelf transport that promotes the exchange of tracers and nutrients to the open sea. The shelf response to cross-shelf winds is studied in the north shelf of the Ebro Delta (Mediterranean Sea), where those winds are prevalent and intense. Offshore winds in the region exhibit strong intensities (wind stress larger than 0.8 Pa) during winter and fall. The monthly average flow observed in a 1 year current meter record at 43.5 m was polarized following the isobaths with the along-shelf variability being larger than the cross-shelf. Prevalent southwestward along-shelf flow was induced by the three-dimensional regional response to cross-shelf winds and the coastal constraint. Seaward near-surface velocities occurred predominantly during offshore wind events. During intense wind periods, the surface cross-shelf water transport exceeded the net along-shelf transport. During typically stratified seasons, the intense cross-shelf winds resulted in a well-defined two-layer flow and were more effective at driving offshore transport than during unstratified conditions. While transfer coefficients between wind and currents were generally around 1%, higher cross-shelf transfer coefficients were observed in the near-inertial band. The regional extent of the resulting surface cold water during energetic cross-shelf winds events was concentrated around the region of the wind jet. Cross-shelf transport due to along-shelf winds was only effective during northeast wind events. During along-shelf wind conditions, the transport was estimated to be between 10 and 50% of the theoretical Ekman transport. © 2015. American Geophysical Union. All Rights Reserved.


Sierra J.P.,Polytechnic University of Catalonia | Sierra J.P.,Center Internacional dInvestigacio dels Recursos Costaners | Casas-Prat M.,Polytechnic University of Catalonia | Casas-Prat M.,Center Internacional dInvestigacio dels Recursos Costaners
Climatic Change | Year: 2014

This study examines the main physical processes related to coastal and port engineering that could be altered by future changes in wave parameters as a consequence of climate change. To estimate the order of magnitude of the potential changes in these processes, several assumptions and simplifications are made and, in most cases, they are assessed by using simple, empirical state-of-the-art expressions. The studied processes are grouped in three categories according to whether they affect beaches, harbors or coastal structures in general. The changes in these processes are estimated as a function of the deepwater variations of the main wave parameters: wave height (H 0), wave period (T) and wave direction (θ 0). A moderate range of variation is assumed for these parameters at deep water (±10 or ±20 % in H 0 and its square root in T, and ±10o in θ 0), taking into account recent studies of future wave projections. The results indicate that potential changes in wave height will strongly affect overtopping discharge, stability and scouring of rubble-mound structures and, to a lesser extent, siltation, wave transmission and longshore sediment transport. Changes in wave direction will affect longshore sediment transport in particular and, at a lower magnitude, processes related to port operability (agitation and siltation). Siltation is the only process affected significantly by changes in T alone. © 2014 The Author(s).


Pallares E.,Polytechnic University of Catalonia | Pallares E.,Center Internacional dInvestigacio dels Recursos Costaners | Sanchez-Arcilla A.,Polytechnic University of Catalonia | Sanchez-Arcilla A.,Center Internacional dInvestigacio dels Recursos Costaners | And 2 more authors.
Continental Shelf Research | Year: 2014

This study has been motivated by the limited accuracy of wave models under short-duration, fetch-limited conditions. This applies particularly to the wave period, in semi-enclosed domains with highly variable wind patterns as along the Catalan coast. The wave model SWAN version 40.91A is used here in three nested grids covering all the North-western Mediterranean Sea with a grid resolution from 9 to 1. km, forced with high resolution wind patterns from BSC (Barcelona Supercomputing Center) for two study periods, the winter 2010 and the spring 2011. The results are validated in eight locations with different types of instrumentations. In order to improve the results, a modification of the whitecapping term parameters is performed. Also the appropriate frequency integral range used to calculate the integral wave parameters is tested to be sure to compare the simulation results and the measurements for the same frequency interval. The results obtained show a clear improvement of the mean wave period and the peak period for the study area, decreasing considerably the negative bias observed previously, while almost no change is observed in wave height due to the proposed modifications. These results can be generalized to the Spanish Mediterranean coast and may be applicable to study areas with similar characteristics as the ones presented here: semi-enclosed domains with fetch-limited conditions and young sea waves. © 2014 Elsevier Ltd.


Sierra J.P.,Polytechnic University of Catalonia | Sierra J.P.,Center Internacional dInvestigacio dels Recursos Costaners | Gonzalez-Marco D.,Polytechnic University of Catalonia | Gonzalez-Marco D.,Center Internacional dInvestigacio dels Recursos Costaners | And 8 more authors.
Renewable Energy | Year: 2013

Lanzarote (Canary Islands, Spain) is a UNESCO Biosphere Reserve (since 1993) located in the Atlantic Ocean. The island is aiming to change its energy production model in order to reduce its dependence on external, fossil-fuel-based energy sources. The local authorities hope to develop an energy production model based on clean, renewable sources, such as wave energy converters (WECs). This study analyses the island's wave energy resources using a 51-year series of data obtained from numerical modelling (hindcast and forecast). The spatial distribution of wave power is analysed using data from nine points around the island. Significant resources (average wave power exceeding 30 kW/m and average annual wave energy of more than 270 MW h/m) are found to the north of the island, as well as to the west and the east (average wave power 25-30 kW/m). Considerable seasonal variability is found, with winters being rather high-energetic and summers quite mild. Variability coefficients are computed in order to select the best locations for WECs; the composition of the resource at each location is examined in terms of sea states in order to evaluate the suitability of WEC installation. Finally, three sites with similar conditions, all located on the north side of the island, are selected as the best candidates for WEC deployment. © 2013 Elsevier Ltd.


Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio dels Recursos Costaners | Del Campo A.,Tecnalia | Espino M.,Polytechnic University of Catalonia | And 4 more authors.
Journal of Marine Systems | Year: 2013

The inclusion of water renewal behaviour in the risk assessment of water pollution for Bilbao harbour (located within the Nervión estuary, southeastern Bay of Biscay) is analysed. Several parameterisations of water renewal (integral and local perspectives), obtained from the numerical evolution analysis of a Eulerian tracer, were used. The local characterisation of water renewal confirmed a strong horizontal spatial variability. In addition, vertical variability on water renewal patterns, due to the 3-dimensional structure of the flow was also appreciated. For the period analysed (August 2008) the water renewal was less effective at the surface, than in deeper waters, because marine breezes counteracted water renewal at the surface, during the observed period. The incidence of this vertical variability, on harbour environmental management, was analysed in implementing a recently developed methodology to evaluate the risk of water pollution. Since this methodology takes into account water renewal, the values of risk of water pollution in Bilbao harbour differed considerably, as a function of the renewal pattern at the surface or within deeper waters. In conclusion, it was found that the water renewal should be parameterised properly, in order to improve environmental management strategies in semi-enclosed water bodies in coastal areas. The findings permitted knowledge to be gained on water renewal behaviour within Bilbao harbour, advancing the framework for the environmental management of harbour waters. © 2011 Elsevier B.V.


Casas-Prat M.,Polytechnic University of Catalonia | Casas-Prat M.,Center Internacional dInvestigacio dels Recursos Costaners | Sierra J.P.,Polytechnic University of Catalonia | Sierra J.P.,Center Internacional dInvestigacio dels Recursos Costaners
Climatic Change | Year: 2012

The effects of climate change are currently a red-hot issue in the scientific community. However, little attention has been paid to the effects of climate change on the wave climate and, in particular, on wave directionality. In this study, we developed a methodology of trend analysis and extrapolation of mean wave climate. We used the parameters of a typical wave rose: frequencies of wave height intervals and directional sectors. The trend over time was estimated by means of linear regression analysis after applying a transformation according to the nature of the (compositional) data. Then, the wave climate was extrapolated up to 2050 assuming the same previously estimated trend and part of the uncertainty was assessed with the bootstrapping technique. Additionally, to get an idea of the magnitude of the consequences of the identified trends, we carried out an impact assessment, in terms of coastal morphodynamics and harbour operability, comparing the present situation with the extrapolation. To assess the impact on coastal morphodynamics, we compared the gradients of long-shore sediment transport to evaluate possible changes in beach retreat/accretion tendency, and to assess harbour operability, we studied the possible impact on harbour agitation in three port case studies. This study was carried out on the Catalan coast (NW Mediterranean Sea) and was based on 40 nodes of 44 years of wave hindcast data. The main impacts on the wave climate were found to be a reduction in the waves coming from the north and northeast and an increase in events coming from the south. This apparently significant change in directionality could result in changes in the prevailing dynamic pattern along more than 70 % of the Catalan coast (e. g. some apparently stable beaches could become erosive) although these results have associated a large uncertainty and are not statistically significant. On the other hand, harbour agitation is expected to increase with statistical significance (by up to 18 % on average) because the studied ports, like most of Catalonia's ports, are oriented towards the south-southwest. © 2012 The Author(s).

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