Carlo Brandini

Remocean System for the Detection of the Reflected Waves from the Costa Concordia Ship Wreck

This paper presents the validation of the Remocean X-band wave radar as a tool for sea state monitoring in coastal zones, by processing the data collected and processed by the radar platform installed at the port of Giglio Island. In particular, the effectiveness of the sea wave height reconstruction has been tested during the storm on November 27, 2012, by focusing on the analysis of the spectral slope and the statistical properties of the ocean waves. A further proof of the effectiveness of the system has been shown by comparing both the estimated sea state parameters and 2-D directional spectrum with the benchmark forecasting models WaveWatchIII (WW3) and Simulating Wave Nearshore (SWAN).

Evaluation of empirical and semi-analytical chlorophyll algorithms in the Ligurian and North Tyrrhenian Seas

Abstract. The estimation of chlorophyll concentration in marine waters is fundamental for a number of scientific and practical purposes. Standard ocean color algorithms applicable to moderate resolution imaging spectroradiometer (MODIS) imagery, such as OC3M and MedOC3, are known to overestimate chlorophyll concentration ([CHL]) in Mediterranean oligotrophic waters. The performances of these algorithms are currently evaluated together with two relatively new algorithms, OC5 and SAM_LT, which make use of more of the spectral information of MODIS data. This evaluation exercise has been carried out using in situ data collected in the North Tyrrhenian and Ligurian Seas during three recent oceanographic campaigns. The four algorithms perform differently in Case 1 and Case 2 waters defined following global and local classification criteria. In particular, the mentioned [CHL] overestimation of OC3M and MedOC3 is not evident for typical Case 1 waters; this overestimation is instead significant in intermediate and Case 2 waters. OC5 and SAM_LT are less sensitive to this problem, and are generally more accurate in Case 2 waters. These results are finally interpreted and discussed in light of a possible operational utilization of the [CHL] estimation methods.

Plastic Debris Occurrence, Convergence Areas and Fin Whales Feeding Ground in the Mediterranean Marine Protected Area Pelagos Sanctuary: A Modeling Approach

The Mediterranean Sea is greatly affected by marine litter. In this area, research on the impact of plastic debris (including microplastics) on biota, particularly large filter-feeding species such as the fin whale (Balaenoptera physalus), is still in its infancy. We investigated the possible overlap between microplastic, mesoplastic and macrolitter accumulation areas and the fin whale feeding grounds in in a pelagic Specially Protected Area of Mediterranean Importance (SPAMI): the Pelagos Sanctuary. Models of ocean circulation and fin whale potential habitat were merged to compare marine litter accumulation with the presence of whales. Additionally, field data on microplastics, mesoplastics and macrolitter abundance and cetacean presence were simultaneously collected. The resulting data were compared, as a multi-layer, with the simulated distribution of plastic concentration and the whale habitat model. These data showed a high occurrence of microplastics (mean: 0.082 items/m2, STD ± 0.079 items/m2) spatial distribution agreed with our modelling results. Areas with high microplastic density significantly overlapped with areas of high macroplastic density. The most abundant polymer detected in all the sampling sites was polyethylene (PE), suggesting fragmentation of larger packaging items as the primary source. To our knowledge, this is the first study in the Pelagos Sanctuary in which the simulated microplastic distribution has been confirmed by field observations. The overlap between the fin whale feeding habitat and the microplastic hot spots is an important contribution for risk assessment of fin whale exposure to microplastics.

X-Band Marine Radar System for High-Speed Navigation Purposes: A Test Case on a Cruise Ship

This letter deals with the investigation of the performance of the REMOCEAN wave-radar system for sea state monitoring, with a specific focus to the navigation purposes. In particular, we present the results of the processing of data collected by an X-band wave-radar installed on the Cruise Roma, during the voyage from Civitavecchia (Italy) to Barcelona (Spain) and return, on 9th and 10th March, 2012. The effectiveness of the REMOCEAN data processing is analyzed by comparing the estimated sea state parameters with the expectation provided by the operational forecasting runs of the WaveWatchIII spectral modeling.

Turbulent behaviour within a coastal boundary layer, observations and modelling at the Isola del Giglio

The hydrodynamics of coastal areas is characterized by the interaction among phenomena occurring at different spatial and temporal scales, such as the interaction of a large-scale ocean current with the local bathymetry and coastline, and local forcing conditions. In order to take into account all relevant phenomena, the study of the hydrodynamics of coastal zones requires a high-spatial and temporal resolution for both observations and simulation of local currents. This resolution can be obtained by using X-band radar, which allows simultaneous measurement of waves and currents in a range of 1–3xa0miles from the coastline, as well as high-resolution numerical models implemented in the area and configured through multiple nesting techniques in order to reach resolutions comparable to such coastal observations. Such an integrated monitoring system was implemented at the Isola del Giglio in 2012, after the accident of the Costa Concordia ship. Results can be used as a cross-validation of data produced independently by radar observations and numerical models. In addition, results give some important insights on the dynamics of the coastal boundary layer, both for what concerns the attenuation in the profile of the depth-averaged velocities which typically occur in turbulent boundary layers, as well as for the production, detachment and evolution of vorticity produced by the interaction of large-scale ocean currents with the coastline and the subsequent time evolution of such boundary layer. This transition between large-scale regional currents and the coastal boundary layer is often neglected in regional forecasting systems, but it has an important role in the ocean turbulence processes.

Extensive analysis of potentialities and limitations of a maximum cross-correlation technique for surface circulation by using realistic ocean model simulations

As shown in the literature, ocean surface circulation can be estimated from sequential satellite imagery by using the maximum cross-correlation (MCC) technique. This approach is very promising since it offers the potential to acquire synoptic-scale coverage of the surface currents on a quasi-continuous temporal basis. However, MCC has also many limits due, for example, to cloud cover or the assumption that Sea Surface Temperature (SST) or other surface parameters from satellite imagery are considered as conservative passive tracers. Also, since MCC can detect only advective flows, it might not work properly in shallow water, where local heating and cooling, upwelling and other small-scale processes have a strong influence. Another limitation of the MCC technique is the impossibility of detecting currents moving along surface temperature fronts. The accuracy and reliability of MCC can be analysed by comparing the estimated velocities with those measured by in situ instrumentation, but the low number of experimental measurements does not allow a systematic statistical study of the potentials and limitations of the method. Instead, an extensive analysis of these features can be done by applying the MCC to synthetic imagery obtained from a realistic numerical ocean model that takes into account most physical phenomena. In this paper a multi-window (MW-) MCC technique is proposed, and its application to synthetic imagery obtained by a regional high-resolution implementation of the Regional Ocean Modeling System (ROMS) is discussed. An application of the MW-MCC algorithm to a real case and a comparison with experimental measurements are then shown.

Diffracted waves from the aground Costa Concordia cruise and detected by the Remocean system

REMOCEAN is a remote sensing system for the wave and current monitoring, based on a nautical X-Band radar, usually deployed for navigation and ship traffic control. Here, we present the results obtained by the analysis of the data collected by the Remocean system, installed in the port of Giglio Island, during the storm of the 27 November 2012. For this test case, the effectiveness of the Remocean wave height reconstruction has been evaluated by analyzing the spectral slope and the statistical properties of the ocean waves and comparing them with independent measures provided by a buoy installed in the proximity the `Costa Concordia shipwreck.

Sampling strategies based on the Singular Value Decomposition for ocean analysis and forecast

In this article we discuss some possible optimal sampling strategies for a simplified ocean model, used as a preliminary tool to understand the observation needs for real analysis and forecasting systems. Indeed, observations are mostly useful for improving the reliability of forecasting models, which require upstream an analysis model in which Data Assimilation techniques are used. In addition, observation networks and in particular in-situ networks are expensive and require careful positioning of a limited number of observation instruments. As in other literature studies, the Singular Value Decomposition has been adopted, which has many advantages, especially when we dispose of a variational assimilation method like the 4D-Var, also because the calculation of Singular Vectors and Singular Values is linked to the availability of tangent linear and adjoint models. SVD has been adopted here as a method for identifying areas where maximum error growth occurs, within which sampling gives particular advantages. However, a SVD-based sampling strategy may not be unique, and we need to introduce other criteria, based on the correlation between points, since the information observed on neighbouring points can be redundant. The criteria adopted are easily replicable in practical applications, and require rather standard studies to obtain prior information (for example, climatological and correlation studies), to be carried out in order to properly design observation networks.

Application of multi-window maximum cross-correlation to the mediterranean sea circulation by using MODIS data

In a previous study an improved Maximum Cross-Correlation technique, called Multi-Window Maximum Cross-Correlation (MW-MCC), was proposed, and applied to noise-free synthetic images in order to show its potential and limits in oceanographic applications. In this work, instead, the application of MW-MCC to high resolution MODIS images, and its capability to provide useful and realistic results for ocean currents, is studied. When applied to real satellite images, the MW-MCC is subject to cloud cover and image quality problems. As a consequence the number of useful MODIS images is greatly reduced. However, for every MODIS image, multiple spec-tral bands are available, and it is possible to apply the MW-MCC algorithm to the same scene as many times as the number of these bands, increasing the possibility of finding valid current vectors. Moreover, the comparison among the results from different spectral bands allows to verify both the consistency of the computed current vectors and the validity of using a spectral band as a good tracer for the ocean circulation. Due to the lack of systematic current measurements in the area considered, it has been not possible to perform an ex-tensive error analysis of the MW-MCC results, although a case study of a comparison between HF radar measurements and MW-MCC data is shown. Moreover, some comparison between numerical ocean model simulations and MW-MCC results are also shown. The coherence of the resulting circulation flow, the high number of current vectors found, the agreement among different spectral bands, and conformity with the currents measured by the HF radars or simulated by hydrodynamic models show the validity of the technique.

Impacts of Ocean Dynamics, Climate Change and Human Pressure on the East African Coast: The Case of Maputo

Coastal erosion and loss of coastal environments are worldwide phenomena. These typical processes occur on different spatial and temporal scales, from river basins to coastlines, and from the ocean-atmosphere system to the global climate scale. All climate change scenarios foresee an increase in the global mean sea level in the next century, from a few tens of centimeters to over a meter. However, these scenarios are not sufficient to explain the accelerating erosion that already occurs today. In coastal areas, such change appears to be linked not only to sea level rise as a direct cause, but also to changing climatic conditions (changes in the rain distribution, winds, sea waves, etc.) and to increased human pressure on land (excessive use of weirs and dams along watercourses, loss of coastal dunes and areas of protective vegetation such as mangroves, etc.). The case of Maputo is quite informative, as none of the known effects of climate change is the main cause of the significant erosion processes that occur there today. Rather, this erosion is attributable to an altered balance between the contributions of sediment from neighboring river basins and to certain effects of coastal dynamics.