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1
Girleanu, Alina, Florin Onea, and Eugen Rusu. "Assessment of the Wind Energy Potential along the Romanian Coastal Zone." Inventions 6, no. 2 (June 4, 2021): 41. http://dx.doi.org/10.3390/inventions6020041.
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The present work aims to provide a comprehensive picture of the wind energy potential that characterizes the Romanian coastal environment using in situ measurements and reanalysis of wind data (ERA5) that cover a 42–year time interval (1979–2020). A total of 16 reference points (both land and offshore) equally distributed along the Romanian sector are used to evaluate the local wind energy potential, targeting in this way several sites where a renewable wind project could be established. Compared to the in situ measurements (land points), the ERA5 dataset underestimates the wind speed by at least 11.57%, this value increasing as we approach the coastline. From the analysis of the spatial maps, it is likely that the wind speed steadily increases from onshore to offshore, with a sharp variation near the coastline being reported. Furthermore, the assessment of some state-of-the-art offshore wind turbines was conducted using 12 systems defined by rated capacity ranging from 2 to 10 MW. Some scenarios were proposed to identify sustainable offshore wind projects to be implemented in the Romanian coastal zone based on these results.
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Jangir, Pramod Kumar, Kevin C. Ewans, and Ian R. Young. "On the Functionality of Radar and Laser Ocean Wave Sensors." Journal of Marine Science and Engineering 10, no. 9 (September 6, 2022): 1260. http://dx.doi.org/10.3390/jmse10091260.
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Ocean wave design criteria are required for the design of offshore platforms and floating systems, which are derived using in situ measurements. However, there is uncertainty regarding the performance of the instruments used for the in situ measurements. The main instruments used by the offshore industry are the Datawell Directional Waverider buoy and Rosemount WaveRadar, with Laser instruments also having been used for specific studies. Recent reports indicate measurements from these three instruments differ in the order of 10% but given the quite disparate nature of the measurements made by these instruments, it is far from clear what the source of this difference is. This paper investigates the wave measurement principles of Radar and Laser instruments using linear wave field simulations to better understand how the instruments perform. The Radar and Laser simulations include modeling electromagnetic signal beam reflections from water surfaces of an area equal to their footprint sizes, considering their beam characteristics and antenna pattern. The study confirms that the Radar underestimates spectral levels at frequencies above 0.5 Hz due to its significantly larger footprint at the water sea surface compared to the Laser (5.25 m vs. 0.15 m). The Laser performs well for almost the entire frequency range for all the cases considered.
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Remmers, Tiny, Fiona Cawkwell, Cian Desmond, Jimmy Murphy, and Eirini Politi. "The Potential of Advanced Scatterometer (ASCAT) 12.5 km Coastal Observations for Offshore Wind Farm Site Selection in Irish Waters." Energies 12, no. 2 (January 9, 2019): 206. http://dx.doi.org/10.3390/en12020206.
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The offshore wind industry has seen unprecedented growth over the last few years. In line with this growth, there has been a push towards more exposed sites, farther from shore, in deeper water with consequent increased investor risk. There is therefore a growing need for accurate, reliable, met-ocean data to identify suitable sites, and from which to base preliminary design and investment decisions. This study investigates the potential of hyper-temporal satellite remote sensing Advanced Scatterometer (ASCAT) data in generating information necessary for the optimal site selection of offshore renewable energy infrastructure, and hence providing a cost-effective alternative to traditional techniques, such as in situ data from public or private entities and modelled data. Five years of the ASCAT 12.5 km wind product were validated against in situ weather buoys and showed a strong correlation with a Pearson coefficient of 0.95, when the in situ measurements were extrapolated with the log law. Temporal variations depicted by the ASCAT wind data followed the same inter-seasonal and intra-annual variations as the in situ measurements. A small diurnal bias of 0.12 m s−1 was observed between the descending swath (10:00 to 12:00) and the ascending swath (20:30 to 22:30), indicating that Ireland’s offshore wind speeds are slightly stronger in the daytime, especially in the nearshore areas. Seasonal maps showed that the highest spatial variability in offshore wind speeds are exhibited in winter and summer. The mean wind speed extrapolated at 80 m above sea level showed that Ireland’s mean offshore wind speeds at hub height ranged between 9.6 m s−1 and 12.3 m s−1. To best represent the offshore wind resource and its spatial distribution, an operational frequency map and a maximum yield frequency map were produced based on the ASCAT wind product in an offshore zone between 20 km and 200 km from the coast. The operational frequency indicates the percentage of time during which the observed local wind speed is between cut-in (3 m/s) and cut-out (25 m/s) for a standard turbine. The operational frequency map shows that the frequency of the wind speed within the cut-in and cut-off range of wind turbines was between 92.4% and 97.2%, while the maximum yield frequency map showed that between 40.6% and 59.5% of the wind speed frequency was included in the wind turbine rated power range. The results showed that the hyper-temporal ASCAT 12.5 km wind speed product (five consecutive years, two observations daily per satellite, two satellites) is representative of wind speeds measured by in situ measurements in Irish waters, and that its ability to depict temporal and spatial variability can assist in the decision-making process for offshore wind farm site selection in Ireland.
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Sultan, Nabil, and Sara Lafuerza. "In situ equilibrium pore-water pressures derived from partial piezoprobe dissipation tests in marine sediments." Canadian Geotechnical Journal 50, no. 12 (December 2013): 1294–305. http://dx.doi.org/10.1139/cgj-2013-0062.
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Excess pore-water pressure has a significant effect on submarine slope stability and sediment deformation, and therefore its in situ equilibrium measurement is crucial in carrying out accurate slope stability assessments and accurately deriving geotechnical design parameters. In situ equilibrium pore-water pressure is usually obtained from pore pressure decay during piezocone tests. However, submarine shelves and slopes are often characterized by the existence of low-permeability (fine-grained) sediments involving long dissipation tests that are an important issue for offshore operational costs. Consequently, short-term and (or) partial dissipation tests are usually performed and in situ equilibrium pore-water pressures are predicted from partial measurements. Using a modified cavity expansion approach, this paper aims to predict for four different sites the in situ equilibrium pore-water pressures. Comparisons between predicted and observed in situ equilibrium pore-water pressures allowed the development of a guide to evaluate the minimum time required to perform short-term dissipation tests for a given marine sediment. The main finding of this Note is that the second derivative of the pore pressure, u, versus the logarithm of time, t, ∂2u/∂ln(t)2 must be positive to calculate accurately the in situ equilibrium pore-water pressures from partial measurements.
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Mizuta, Darien Danielle, and Gary H. Wikfors. "Depth Selection and In Situ Validation for Offshore Mussel Aquaculture in Northeast United States Federal Waters." Journal of Marine Science and Engineering 7, no. 9 (August 29, 2019): 293. http://dx.doi.org/10.3390/jmse7090293.
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As mariculture progresses offshore in the US Exclusive Economic Zone, technical and ecological challenges need to be overcome, such as the choice of suitable sites that favor the production of target species. The offshore culture of blue mussels, Mytilus edulis, is performed with submerged longlines and mussels need to withstand more motion than on coastal sites. Temperature affects the ability of the byssus to adhere to farming rope, while chlorophyll concentration provides an estimation of food availability. Together, these are important factors in predicting the suitability of offshore mussel farms. To identify suitable depth of submersion for mussel ropes in New England federal waters, historical oceanographic data of temperature and chlorophyll a from 2005 to 2012 were used. The results suggest that mussel ropes were submerged during summer to a minimum depth of 15 m in northern and a 20-m depth in southern areas of New England where temperature is at a species-optimum and phytoplankton biomass is abundant. For the site offshore Massachusetts, in situ biodeposition measurements validated predicted depth, confirming satisfactory mussel performance. Promising local areas have shallow thermoclines, such as offshore Long Island, Cape Ann and New Hampshire. Recommended depths can be adjusted to future temperature increases associated with climate change.
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Calore, Daniele, and Nicola Fraticelli. "State of the Art Offshore In Situ Monitoring of Microplastic." Microplastics 1, no. 4 (November 2, 2022): 640–50. http://dx.doi.org/10.3390/microplastics1040044.
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Microplastics make up a significant amount of the overall quantity of plastic debris that is present in seawater. However, their detection and monitoring at sea is cost-inefficient and challenging; typically, it consists of water sampling with special manta nets, followed by long (i.e., weeks) laboratory analysis to obtain valid results. The analysis of the state-of-the-art technologies capable of monitoring/detecting microplastics in the sea (typically in coastal areas) presented in this paper shows that there are currently no specific tools to obtain quick measurements. The classic multiparametric probes are useless and the contribution of their relative chemical–physical parameters to determine the presence of microplastics in water is insignificant. The evolution in the last decade of hardware and software tools for capturing hologram images and related post-processing seems to be one of the most effective methods available currently for the rapid detection of microplastics in seawater. In particular, some results of monitoring campaigns carried out in the Adriatic Sea using this type of technology are reported. The acquired data are analyzed and discussed, highlighting their strengths and weaknesses, with indications of the possible methodologies that could be used to improve these systems.
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Saviano, Simona, Anastasia Angela Biancardi, Florian Kokoszka, Marco Uttieri, Enrico Zambianchi, Luis Alberto Cusati, Andrea Pedroncini, and Daniela Cianelli. "HF Radar Wind Direction: Multiannual Analysis Using Model and HF Network." Remote Sensing 15, no. 12 (June 8, 2023): 2991. http://dx.doi.org/10.3390/rs15122991.
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HF radar systems have the potential to measure the wind direction, in addition to surface currents and wave fields. However, studies on HF radar for wind direction determination are rare in the scientific literature. Starting with the results presented in Saviano et al. (2021), we here expand on the reliability of the multiannual wind direction data retrieved over two periods, from May 2008 to December 2010 and from January to December 2012, by a network of three SeaSonde high-frequency (HF) radars operating in the Gulf of Naples (Central Tyrrhenian Sea, Western Mediterranean Sea). This study focuses on the measurements obtained by each antenna over three range cells along a coast–offshore transect, pointing to any potential geographically dependent measurement. The scarcity of offshore wind measurements requires the use of model-generated data for comparative purposes. The data here used are obtained from the Mediterranean Wind–Wave Model, which provides indications for both wave and wind parameters, and the ERA5@2km wind dataset obtained by dynamically downscaling ERA5 reanalysis. These data are first compared with in situ data and subsequently with HF-retrieved wind direction measurements. The analysis of the overall performance of the HF radar network in the Gulf of Naples confirms that the HF radar wind data show the best agreement when the wind speed exceeds a 5 m/s threshold, ensuring a sufficiently energetic surface wave field to be measured. The results obtained in the study suggest the necessity of wind measurements in offshore areas to validate the HF radar wind measurements and to improve the extraction algorithms. The present work opens up further investigations on the applications of wind data from SeaSonde HF radars as potential monitoring platforms, both in coastal and offshore areas.
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Zhang, Hong, Xiaolei Liu, Anduo Chen, Weijia Li, Yang Lu, and Xingsen Guo. "Design and Application of an In Situ Test Device for Rheological Characteristic Measurements of Liquefied Submarine Sediments." Journal of Marine Science and Engineering 9, no. 6 (June 9, 2021): 639. http://dx.doi.org/10.3390/jmse9060639.
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Liquefied submarine sediments can easily lead to submarine landslides and turbidity currents, and cause serious damage to offshore engineering facilities. Understanding the rheological characteristics of liquefied sediments is critical for improving our knowledge of the prevention of submarine geo-hazards and the evolution of submarine topography. In this study, an in situ test device was developed to measure the rheological properties of liquefied sediments. The test principle is the shear column theory. The device was tested in the subaqueous Yellow River delta, and the test results indicated that liquefied sediments can be regarded as “non-Newtonian fluids with shear thinning characteristics”. Furthermore, a laboratory rheological test was conducted as a contrast experiment to qualitatively verify the accuracy of the in situ test data. Through the comparison of experiments, it was proved that the use of the in situ device in this paper is suitable and reliable for the measurement of the rheological characteristics of liquefied submarine sediments. Considering the fact that liquefaction may occur in deeper water (>5 m), a work pattern for the device in the offshore area is given. This novel device provides a new way to test the undrained shear strength of liquefied sediments in submarine engineering.
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Platis, Andreas, Marie Hundhausen, Astrid Lampert, Stefan Emeis, and Jens Bange. "The Role of Atmospheric Stability and Turbulence in Offshore Wind-Farm Wakes in the German Bight." Boundary-Layer Meteorology 182, no. 3 (October 10, 2021): 441–69. http://dx.doi.org/10.1007/s10546-021-00668-4.
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AbstractAirborne meteorological in situ measurements as well as stationary measurements at the offshore masts FINO1 and FINO3 in the German Bight are evaluated in order to examine the hypothesis that the wake dissipation downstream of large offshore wind farms depends on atmospheric stability. A long-term study of the mast data for the years 2016 and 2017 demonstrates a clear dependence of stability on the wind direction. Stable conditions are predominantly expected during southerly winds coming from the land. The analysis of various stability and turbulence criteria shows that the lapse rate is the most robust parameter for stability classification in the German Bight, but further implies that stability depends on the measurement height. A near-surface (0 to 30 m), predominantly convective, layer is present and more stable conditions are found aloft (55 to 95 m). Combing the stability data with the airborne measurements of the offshore wind-farm wakes reveals the trend of a correlation between longer wake lengths and an increase in the initial wind-speed deficit downwind of a wind farm with stronger thermal stability. However, the stability correlation criteria with the wake length downstream of the four investigated wind farms, Godewind, Amrumbank West, Meerwind Süd/Ost, and Nordsee Ost, contain large variance. It is assumed that the observed scattering is due to the influence of the wind-farm architecture and temperature inversions around hub height. These, however, are crucial for the classification of stability and illustrate the complexity of a clear stability metric.
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Volker, P. J. H., J. Badger, A. N. Hahmann, and S. Ott. "The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF." Geoscientific Model Development Discussions 8, no. 4 (April 29, 2015): 3481–522. http://dx.doi.org/10.5194/gmdd-8-3481-2015.
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Abstract. We describe the theoretical basis, implementation and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP), uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.
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Gandoin, Rémi, and Jorge Garza. "Underestimation of strong wind speeds offshore in ERA5: evidence, discussion and correction." Wind Energy Science 9, no. 8 (August 19, 2024): 1727–45. http://dx.doi.org/10.5194/wes-9-1727-2024.
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Abstract. Offshore wind power plants have become an important element of the European electrical grid. Studies of metocean site conditions (wind, sea state, currents, water levels) form a key input to the design of these large infrastructure projects. Such studies rely heavily on reanalysis datasets which provide decades-long model time series over large areas. In turn, these time series are used for assessing wind, water levels and wave conditions and are thereby key inputs to design activities such as calculations of fatigue loads and extreme loads and platform elevations. In this article, we address a known deficiency of one these reanalysis datasets, ERA5, namely that it underestimates strong wind speeds offshore. If left uncorrected, this poses a design risk (high and extreme wind, waves and water level conditions are underestimated). Firstly, comparisons are made against CFSR/CFSv2 reanalyses as well as high-quality wind-energy-specific in situ measurements from floating lidar systems. Then, the ERA5 surface drag formulation and its sea state dependency are analysed in detail, the conditions of the bias identified, and a correction method is suggested. The article concludes with proposing practical and simple ways to incorporate publicly available, high-quality wind energy measurement datasets in air–sea interaction studies alongside legacy measurements such as met buoys.
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Volker, P. J. H., J. Badger, A. N. Hahmann, and S. Ott. "The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF." Geoscientific Model Development 8, no. 11 (November 18, 2015): 3715–31. http://dx.doi.org/10.5194/gmd-8-3715-2015.
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Abstract. We describe the theoretical basis, implementation, and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP), uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated for a neutral atmospheric boundary layer against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements, and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.
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Kardakaris, Kimon, Ifigeneia Boufidi, and Takvor Soukissian. "Offshore Wind and Wave Energy Complementarity in the Greek Seas Based on ERA5 Data." Atmosphere 12, no. 10 (October 18, 2021): 1360. http://dx.doi.org/10.3390/atmos12101360.
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In this work, 20 years (2000–2019) of ERA5 wave and wind data are analyzed and evaluated for the Greek Seas by means of in-situ measurements derived from the POSEIDON marine monitoring system. Four different statistical measures were used at six locations, where in-situ wind and wave measurements are available from oceanographic buoys. Furthermore, the ERA5 wind and wave datasets were utilized for the estimation of the available wind and wave energy potential for the Greek Seas, as well as for the assessment of complementarity and synergy between the two resources. In this respect, an event-based approach was adopted. The spatial distribution of the available wind and wave energy potential resembles qualitatively and quantitatively the distributions derived from other reanalysis datasets. Locations with high synergy and complementarity indices were identified taking into account water depth. Finally, taking into consideration a particular offshore wind turbine power curve and the power matrix of the PELAMIS wave energy converter, the estimation of the combined energy potential on a mean annual basis is performed.
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Han, Wei-Chung, Yi-Wei Lu, and Sheng-Chung Lo. "Seismic prediction of soil distribution for the Chang-Bin offshore wind farm in the Taiwan Strait." Interpretation 8, no. 4 (August 31, 2020): T727—T737. http://dx.doi.org/10.1190/int-2020-0020.1.
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Direct soil measurements are limited to borehole locations and are therefore sparse in the oceans. To effectively characterize the soil distributions for the Chang-Bin offshore wind farm, which is an area with the greatest wind energy potential in the Taiwan Strait, we have developed a workflow to predict the soil distribution in the subsurface based on integrated analysis of seismic data and borehole data. First, we characterize the key seismic units and their seismic response in order to understand the regional stratigraphy. Then, we correlate the soil types to each stratigraphic unit as the constraint for the input and quality control to train a neural network based on seismic multiattribute analysis. Finally, we develop a neural network that is suitable for soil prediction in the Chang-Bin offshore wind farm. Five seismic units identified from the seismic profiles reveal that the regional stratigraphy has been greatly affected by sea-level change and the sediment transportation process. Confirmed by independent in situ borehole data, the neural network is considered reliable up to 60 m below the seafloor, whereas decreased signal-to-noise ratios at greater depths lead to poorer prediction accuracy. Compared to previous studies that mainly are based on high-quality 3D seismic and well logging data, our method can predict the soil distribution by analyzing 2D seismic profiles and simplified soil layers alone. The prediction results reveal detailed lithologic variations that are tested by in situ borehole measurements. Therefore, we are confident that this approach could effectively obtain the soil distribution prediction and thus reduce the costs in offshore engineering applications.
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Khachatrian, Eduard, Patricia Asemann, Lihong Zhou, Yngve Birkelund, Igor Esau, and Benjamin Ricaud. "Exploring the Potential of Sentinel-1 Ocean Wind Field Product for Near-Surface Offshore Wind Assessment in the Norwegian Arctic." Atmosphere 15, no. 2 (January 24, 2024): 146. http://dx.doi.org/10.3390/atmos15020146.
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The exploitation of offshore wind resources is a crucial step towards a clean energy future. It requires an advanced approach for high-resolution wind resource evaluations. We explored the suitability of the Sentinel-1 Level-2 OCN ocean wind field (OWI) product for offshore wind resource assessments. The SAR data were compared to in situ observations and three reanalysis products: the global reanalysis ERA5 and two regional reanalyses CARRA and NORA3. This case study matches 238 scenes from 2022 for the Goliat station, an oil platform located 85 km northwest of Hammerfest in the Barents Sea, where a new offshore wind park has been proposed. The analysis showed that despite their unique limitations in spatial and temporal resolutions, all data sources have similar statistical properties (RMSE, correlation coefficient, and standard deviation). The Weibull parameters characterizing the wind speed distributions showed strong similarities between the Sentinel-1 and all reanalysis data. The Weibull parameters of the in situ measurements showed an underestimation of wind speed compared to all other sources. Comparing the full reanalysis datasets with the subsets matching the SAR scenes, only slight changes in Weibull parameters were found, indicating that, despite its low temporal resolution, the Sentinel-1 Level 2 OWI product can compete with the more commonly used reanalysis products in the estimation of offshore wind resources. Its high spatial resolution, which is unmatched by other methods, renders it especially valuable in offshore areas close to complex coastlines and in resolving weather events at a smaller scale.
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Lampert, Astrid, Konrad Bärfuss, Andreas Platis, Simon Siedersleben, Bughsin Djath, Beatriz Cañadillas, Robert Hunger, et al. "In situ airborne measurements of atmospheric and sea surface parameters related to offshore wind parks in the German Bight." Earth System Science Data 12, no. 2 (April 27, 2020): 935–46. http://dx.doi.org/10.5194/essd-12-935-2020.
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Abstract. Between 6 September 2016 and 15 October 2017, meteorological measurement flights were conducted above the German Bight in the framework of the project WIPAFF (Wind Park Far Field). The scope of the measurements was to study long-range wakes with an extent larger than 10 km behind entire wind parks, and to investigate the interaction of wind parks and the marine atmospheric boundary layer. The research aircraft Dornier 128 of the Technische Universität (TU) Braunschweig performed in total 41 measurement flights during different seasons and different stability conditions. The instrumentation consisted of a nose boom with sensors for measuring the wind vector, temperature and humidity, and additionally sensors for characterizing the water surface, a surface temperature sensor, a laser scanner and two cameras in the visible and infrared wavelength range. A detailed overview of the aircraft, sensors, data post-processing and flight patterns is provided here. Further, averaged profiles of atmospheric parameters illustrate the range of conditions. The potential use of the data set has been shown already by first publications. The data are publicly available in the world data centre PANGAEA (https://doi.org/10.1594/PANGAEA.902845; Bärfuss et al., 2019a).
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Yildirir, Victoria, Eugen Rusu, and Florin Onea. "Wind Energy Assessments in the Northern Romanian Coastal Environment Based on 20 Years of Data Coming from Different Sources." Sustainability 14, no. 7 (April 2, 2022): 4249. http://dx.doi.org/10.3390/su14074249.
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Based on the fact that the wind speed tends to increase as we go from onshore to offshore, the aim of this work is to perform an analysis of a Romanian coastal sector located near the Danube Delta. Over the course of 20 years (2001–2020), in situ observations and reanalysis data (ERA5 and MERRA-2) of the local wind conditions were evaluated from a meteorological and renewable point of view. This evaluation includes two onshore sites (Galati and Tulcea), one site located near the shoreline (Sulina) and also two offshore sites defined at 64 and 126 km from the coastline. From the comparison with in situ measurements, it was found that ERA5 shows a better agreement with the onshore sites, while for the Sulina site the MERRA-2 is more accurate. Additionally, it was highlighted that by using only four values per day of reanalysis data (00:06:12:18 UTC), the average wind speed is similar with the one from the hourly data. As for a wind turbine performance (hub height of 100 m), in the case of the onshore sites the downtime period is much higher during the night (up to 63%) compared to only 23% indicated by the offshore ones during the entire day.
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Li, Xinba, Panagiotis Mitsopoulos, Yue Yin, and Malaquias Peña. "SARAL-AltiKa Wind and Significant Wave Height for Offshore Wind Energy Applications in the New England Region." Remote Sensing 13, no. 1 (December 25, 2020): 57. http://dx.doi.org/10.3390/rs13010057.
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The SARAL-AltiKa dataset was evaluated for refined offshore wind energy resources assessment and potential metocean monitoring capability in the Southern New England region. Surface wind speed and Significant Wave Height (Hs) products were assessed with corresponding variables from buoy observations for 2014–2019. To increase the sample size, this study analyzed and applied an approach to collect data around the reference buoys beyond the satellite footprint at the expense of a bias increment. The study corroborated the accuracy of the SARAL-AltiKa measurements for the offshore area of interest and added details for stations closer to the coast compared with past studies. A proportional bias with underestimation of high values of Hs was found in coastal sites. Wind speed estimates on the other hand appear to be less sensitive to the closeness to the coast. The empirical relationship between wind strength and Hs in the buoy observations is reproduced to a large extent by the AltiKa measurements in locations where land contamination is minimal. The histograms of surface wind and Hs are well described by the Weibull distribution and the shape and scale parameters closely resemble those of the histograms of the collocated in situ observations. We use these results to extrapolate the winds to a target domain with no in situ observations for wind energy resource estimation.
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Dudley, John W., Arjan van der Linden, and Kok Gin Mah. "Predicting Accelerating Subsidence Above The Highly Compacting Luconia Carbonate Reservoirs, Offshore Sarawak Malaysia." SPE Reservoir Evaluation & Engineering 12, no. 01 (February 26, 2009): 104–15. http://dx.doi.org/10.2118/109190-pa.
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Summary Sarawak Shell Berhad has a number of offshore gas fields that produce from the Luconia carbonate formation, which can exhibit high-compressibility pore-collapse deformation. Recent accelerated subsidence has been observed at several of these fields, which extrapolates to final subsidence values well above previous estimates. This paper describes a geomechanical study involving core work to determine if the Luconia formation compressibility is sensitive to brine flow from the rising aquifer and a 3D geomechanical finite-element model developed to predict future subsidence and lateral movements for the F23 platform. Compaction tests were performed on the Luconia core from three different gas fields. Tests on twin plugs were conducted—one plug undergoing a standard uniaxial zero-lateral-strain compaction test, while its twin has several pore volumes of simulated-formation brine flowed through it (at virgin in-situ stress conditions) before the compaction loading. Four sets of compaction tests on twin plugs were completed. The higher-porosity samples showed characteristic pore-collapse behavior consistent with previous measurements on Luconia mouldic limestone core. No sensitivity to brine flow was observed. In-situ compaction logs in the field also do not show increased compressibility in sections flooded by the rising gas-water contact (GWC). The geomechanical model uses a relatively simple structural model comprised of four layers—two overburden formations, the Luconia carbonate and one underburden formation. A nonlinear deformation model for the Luconia formation captures the accelerating pore-collapse response observed in the core and in-situ compaction measurements. The model is calibrated to GPS-measured platform subsidence and is consistent with measured core- and field-compaction properties. The results predict that platform subsidence rates with depletion would level off, with a maximum subsidence of 18.5 ft +/- 1 ft at an abandonment pressure of 300 psi. Platform subsidence in the two years following the work continues to follow the predicted values. This work illustrates the importance of integrated geomechanical core testing, field-monitoring measurements, and modeling to accurately predict compaction and subsidence effects in highly compacting environments.
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Henkel, Maximilian, Wout Weijtjens, and Christof Devriendt. "Fatigue Stress Estimation for Submerged and Sub-Soil Welds of Offshore Wind Turbines on Monopiles Using Modal Expansion." Energies 14, no. 22 (November 12, 2021): 7576. http://dx.doi.org/10.3390/en14227576.
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The design of monopile foundations for offshore wind turbines is most often driven by fatigue. With the foundation price contributing to the total price of a turbine structure by more than 30%, wind farm operators seek to gain knowledge about the amount of consumed fatigue. Monitoring concepts are developed to uncover structural reserves coming from conservative designs in order to prolong the lifetime of a turbine. Amongst promising concepts is a wide array of methods using in-situ measurement data and extrapolating these results to desired locations below water surface and even seabed using models. The modal decomposition algorithm is used for this purpose. The algorithm obtains modal amplitudes from acceleration and strain measurements. In the subsequent expansion step these amplitudes are expanded to virtual measurements at arbitrary locations. The algorithm uses a reduced order model that can be obtained from either a FE model or measurements. In this work, operational modal analysis is applied to obtain the required stress and deflection shapes for optimal validation of the method. Furthermore, the measurements that are used as input for the algorithms are constrained to measurements from the dry part of the substructure. However, with subsoil measurement data available from a dedicated campaign, even validation for locations below mud-line is possible. After reconstructing strain history in arbitrary locations on the substructure, fatigue assessment over various environmental and operational conditions is carried out. The technique is found capable of estimating fatigue with high precision for locations above and below seabed.
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Di, Sheng Jie, Ming Yuan Wang, Zhi Gang Shan, and Hai Bo Jia. "Soil Liquefaction Evaluation of Offshore Site Based on In Situ Shear Wave Velocity Measurements." Applied Mechanics and Materials 405-408 (September 2013): 470–73. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.470.
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A procedure for evaluating liquefaction resistance of soils based on the shear wave velocity measurements is outlined in the paper. The procedure follows the general formal of the Seed-Idriss simplified procedure. In addition, it was developed following suggestions from industry, researchers, and practitioners. The procedure correctly predicts moderate to high liquefaction potential for over 95% of the liquefaction case histories. The case study for the site of offshore wind farm in Jiangsu province is provided to illustrate the application of the proposed procedure. The feature of the soils and the shear wave velocity in-situ tested in site are discussed and the liquefaction potential of the layer is evaluated. The application shows that the layers of the non-cohesive soils in the depths 3-11m may be liquefiable according to the procedure.
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Versteijlen, W. G., K. N. van Dalen, A. V. Metrikine, and L. Hamre. "Assessing the small-strain soil stiffness for offshore wind turbines based on in situ seismic measurements." Journal of Physics: Conference Series 524 (June 16, 2014): 012088. http://dx.doi.org/10.1088/1742-6596/524/1/012088.
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Shimizu, T., Y. Yamamoto, and N. Tenma. "Methane-Hydrate-Formation Processes in Methane/Water Bubbly Flows." SPE Journal 22, no. 03 (October 5, 2016): 746–55. http://dx.doi.org/10.2118/176156-pa.
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Summary Offshore natural-gas production from methane-hydrate (MH) reservoirs has received considerable attention. In this study, the offshore production method is briefly described, followed by the flow loop experiments performed to investigate the formation processes of MH in methane-in-water bubbly flows. Transient processes of phase transformation are characterized by phase paths, flow morphologies, pump heads, and in-situ particle-size measurements. It is realized that an MH slurry is generated by MH shells covering unconverted bubbles, whereas it can be transformed into a colloidal flow with fine crystalline particles under an intense turbulent shear. This study suggests that, in practice, the flow pattern under MH formation would be determined by the phase path and the flow velocity in the pipeline, which is one of the important factors considered in the evaluation of flow-assurance risks.
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Colgan, William, Agnes Wansing, Kenneth Mankoff, Mareen Lösing, John Hopper, Keith Louden, Jörg Ebbing, et al. "Greenland Geothermal Heat Flow Database and Map (Version 1)." Earth System Science Data 14, no. 5 (May 12, 2022): 2209–38. http://dx.doi.org/10.5194/essd-14-2209-2022.
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Abstract. We compile and analyze all available geothermal heat flow measurements collected in and around Greenland into a new database of 419 sites and generate an accompanying spatial map. This database includes 290 sites previously reported by the International Heat Flow Commission (IHFC), for which we now standardize measurement and metadata quality. This database also includes 129 new sites, which have not been previously reported by the IHFC. These new sites consist of 88 offshore measurements and 41 onshore measurements, of which 24 are subglacial. We employ machine learning to synthesize these in situ measurements into a gridded geothermal heat flow model that is consistent across both continental and marine areas in and around Greenland. This model has a native horizontal resolution of 55 km. In comparison to five existing Greenland geothermal heat flow models, our model has the lowest mean geothermal heat flow for Greenland onshore areas. Our modeled heat flow in central North Greenland is highly sensitive to whether the NGRIP (North GReenland Ice core Project) elevated heat flow anomaly is included in the training dataset. Our model's most distinctive spatial feature is pronounced low geothermal heat flow (< 40 mW m−2) across the North Atlantic Craton of southern Greenland. Crucially, our model does not show an area of elevated heat flow that might be interpreted as remnant from the Icelandic plume track. Finally, we discuss the substantial influence of paleoclimatic and other corrections on geothermal heat flow measurements in Greenland. The in situ measurement database and gridded heat flow model, as well as other supporting materials, are freely available from the GEUS Dataverse (https://doi.org/10.22008/FK2/F9P03L; Colgan and Wansing, 2021).
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Isaac, George A., Terry Bullock, Jennifer Beale, and Steven Beale. "Characterizing and Predicting Marine Fog Offshore Newfoundland and Labrador." Weather and Forecasting 35, no. 2 (February 17, 2020): 347–65. http://dx.doi.org/10.1175/waf-d-19-0085.1.
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Abstract As several review papers have concluded, marine fog is imperfectly characterized, and quantitative visibility forecasts are difficult to produce accurately. Some unique measurements have been made offshore Newfoundland and Labrador of the climatology of occurrence and the microphysical characteristics of marine, or open-ocean, fog. Based on measurements made at an offshore installation over 21 years, the percent of time with visibilities less than 0.5 n mi or approximately 1 km (1 n mi ≈ 1.85 km) reaches 45% in July, with a low of about 5% during the winter. The occurrence of fog is mainly due to warm air advection, with the highest frequency occurring with wind directions from over the warm Gulf Stream, and with air temperatures about 2°C warmer than the sea surface temperature. There is no diurnal variation in the frequency of occurrence of fog. The microphysical properties of the fog have been documented in the summer time frame, with over 550 h of in situ measurements made offshore with fog liquid water content greater than 0.005 g m−3. The fog droplet number concentration spectra peaks near 6 μm, with a secondary peak near 25–40 μm, which typically contains most of the liquid water content. The median droplet concentration is approximately 70–100 cm−3. The microphysical spectra have been used to develop a new NWP visibility parameterization scheme, and this scheme is compared with other parameterizations currently in use.
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Woo, Hye-Jin, and Kyung-Ae Park. "Inter-Comparisons of Daily Sea Surface Temperatures and In-Situ Temperatures in the Coastal Regions." Remote Sensing 12, no. 10 (May 16, 2020): 1592. http://dx.doi.org/10.3390/rs12101592.
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In this study, seven, global, blended, sea surface temperature (SST) analyses, including Operational SST and Sea Ice Analysis (OSTIA), Canadian Meteorological Centre (CMC) analysis, Optimum Interpolation SST (OISST), Remote Sensing System (REMSS) analysis, Multi-scale Ultra-high Resolution SST (MURSST), Merged Satellite and In situ Data Global Daily SST (MGDSST), and Geo-Polar Blended SST (Blended SST) were conducted. In-situ temperature measurements were used for the years 2014–2018, from 35 narrowly-spaced buoys distributed along the Korean Peninsula coast, to investigate how well the SST analyses represent the temperatures at the coastal regions. Contrary to the overall accuracy of the SSTs in the global ocean and offshore regions, the root-mean-square errors for the analyses were relatively large over 1.27 K. Specifically, all SST analyses resulted in warm biases over 0.31 K, which became quite distinctive in the western and the southwestern coastal regions. Investigation of the errors identified relationships with the coastal zones of vigorous tidal mixing, shallow bathymetry, and absence of microwave measurements. Overall, temporal wavelet coherency between in-situ measurements and SST products revealed high coherency of greater than 0.8 in periods longer than 180 days, however, low coherency (<0.5) in the period shorter than 10 days was observed. Inter-comparisons between the SST analyses illustrated clear spatial differences in the correlations at both the coastal regions, along the southwestern coast of the Korean Peninsula and in the frontal regions, and in the marginal seas of the Northwest Pacific. Overall, the results emphasized on the importance of using real-time in-situ measurements as much as possible, to overcome the increasing SST errors in coastal regions.
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Ye, Haijun, Junmin Li, Bo Li, Junliang Liu, Danling Tang, Wuyang Chen, Hongqiang Yang, et al. "Evaluation of CFOSAT Scatterometer Wind Data in Global Oceans." Remote Sensing 13, no. 10 (May 14, 2021): 1926. http://dx.doi.org/10.3390/rs13101926.
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The China-France Oceanography SATellite (CFOSAT), launched on 29 October 2018, is a joint mission developed by China and France. To evaluate the CFOSAT wind product, L2B swath data with a spatial resolution of 25 × 25 km were compared with in situ measurements between December 2018 and December 2020. The in situ measurements were collected from 217 buoys. All buoy winds were adjusted to 10 m height using a simple logarithmic correction method. The temporal and spatial separations between the CFOSAT and in situ measurements were restricted to less than 30 min and 0.25°. The results indicate that the CFOSAT wind retrievals agree well with the buoy measurements. The root mean square errors (RMSEs) of wind vectors were 1.39 m s−1 and 34.32° and negligible biases were found. In the near shore under rain-free conditions, the RMSEs were enhanced to 1.42 m s−1 and 33.43°. Similarly, the RMSEs were reduced to 1.16 m s−1 and 30.41° offshore after the rain effect was removed. After winds less than 4 m s−1 were removed, the RMSE of wind directions was reduced to 19.69°. The effects of significant wave height, air-sea temperature difference, sea surface temperature, atmospheric pressure and ocean surface current on the wind residuals were assessed. The performance of wind retrievals under the passage of tropical cyclones was evaluated. The evaluation results show that the CFOSAT wind retrievals satisfy the accuracy requirements of scientific research, although some improvements are needed to enhance the performance.
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Delauney, L., C. Compère, and M. Lehaitre. "Biofouling protection for marine environmental sensors." Ocean Science 6, no. 2 (May 18, 2010): 503–11. http://dx.doi.org/10.5194/os-6-503-2010.
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Abstract. These days, many marine autonomous environment monitoring networks are set up in the world. These systems take advantage of existing superstructures such as offshore platforms, lightships, piers, breakwaters or are placed on specially designed buoys or underwater oceanographic structures. These systems commonly use various sensors to measure parameters such as dissolved oxygen, turbidity, conductivity, pH or fluorescence. Emphasis has to be put on the long term quality of measurements, yet sensors may face very short-term biofouling effects. Biofouling can disrupt the quality of the measurements, sometimes in less than a week. Many techniques to prevent biofouling on instrumentation are listed and studied by researchers and manufacturers. Very few of them are implemented on instruments and of those very few have been tested in situ on oceanographic sensors for deployment of at least one or two months. This paper presents a review of techniques used to protect against biofouling of in situ sensors and gives a short list and description of promising techniques.
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Delauney, L., C. Compère, and M. Lehaitre. "Biofouling protection for marine environmental sensors." Ocean Science Discussions 6, no. 3 (December 7, 2009): 2993–3018. http://dx.doi.org/10.5194/osd-6-2993-2009.
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Abstract. These days, many marine autonomous environment monitoring networks are set up in the world. These systems take advantage of existing superstructures such as offshore platforms, lightships, piers, breakwaters or are placed on specially designed buoys or underwater oceanographic structures. These systems commonly use various sensors to measure parameters such as dissolved oxygen, turbidity, conductivity, pH or fluorescence. Emphasis has to be put on the long term quality of measurements, yet sensors may face very short-term biofouling effects. Biofouling can disrupt the quality of the measurements, sometimes in less than a week. Many techniques to prevent biofouling on instrumentation are listed and studied by researchers and manufacturers. Very few of them are implemented on instruments and of those very few have been tested in situ on oceanographic sensors for deployment of at least one or two months. This paper presents a review of techniques used to protect against biofouling of in situ sensors and will give a short list and description of promising techniques.
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Macini, Paolo, and Ezio Mesini. "Measuring Reservoir Compaction Through Radioactive Marker Technique." Journal of Energy Resources Technology 124, no. 4 (November 20, 2002): 269–75. http://dx.doi.org/10.1115/1.1506700.
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Radioactive Marker Technique (RMT), an in-situ method to measure reservoir rock compaction and to evaluate uniaxial compressibility coefficients Cm, is examined here. Recent field applications seems to confirm that RMT-derived Cm’s match with sufficient precision with those calculated from land subsidence observed over the field by means of geodetic surveys, but are not always in good agreement with those derived from lab measurements. In particular, here is reported an application of RMT in the Italian Adriatic offshore, which highlights the discrepancies of Cm’s measurements from lab and RMT. At present, these discrepancies aren’t thoroughly understood, so, from an applicative standpoint, it is still necessary to perform a critical comparison and integration between both set of data.
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Hauge, Vera Louise, and Odd Kolbjørnsen. "Bayesian inversion of gravimetric data and assessment of CO2 dissolution in the Utsira Formation." Interpretation 3, no. 2 (May 1, 2015): SP1—SP10. http://dx.doi.org/10.1190/int-2014-0193.1.
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Offshore gravimetric monitoring has been introduced as a complement to seismic monitoring of fields with moving fluids. The Sleipner field in the North Sea is a fully operational carbon capture and storage facility, where [Formula: see text] is injected for storage. Gravimetric measurements are one of the geophysical monitoring methods applied, and the data have been used to estimate the in situ density and dissolution of the [Formula: see text]. We defined a Bayesian inversion of gravimetric data, and we used this to analyze gravimetric data at Sleipner field. In our approach, we included spatial uncertainty in the model and performed a Bayesian analysis of the in situ [Formula: see text] density and dissolution. We also analyzed the impact of mass changes due to gas production from the Ty Formation. Our estimates were comparable with published results.
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Hatfield, Daniel, Charlotte Bay Hasager, and Ioanna Karagali. "Vertical extrapolation of Advanced Scatterometer (ASCAT) ocean surface winds using machine-learning techniques." Wind Energy Science 8, no. 4 (April 28, 2023): 621–37. http://dx.doi.org/10.5194/wes-8-621-2023.
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Abstract. The increasing demand for wind energy offshore requires more hub-height-relevant wind information, while larger wind turbine sizes require measurements at greater heights. In situ measurements are harder to acquire at higher atmospheric levels; meanwhile the emergence of machine-learning applications has led to several studies demonstrating the improvement in accuracy for vertical wind extrapolation over conventional power-law and logarithmic-profile methods. Satellite wind retrievals supply multiple daily wind observations offshore, however only at 10 m height. The goal of this study is to develop and validate novel machine-learning methods using satellite wind observations and near-surface atmospheric measurements to extrapolate wind speeds to higher heights. A machine-learning model is trained on 12 years of collocated offshore wind measurements from a meteorological mast (FINO3) and space-borne wind observations from the Advanced Scatterometer (ASCAT). The model is extended vertically to predict the FINO3 vertical wind profile. Horizontally, it is validated against the NORwegian hindcast Archive (NORA3) mesoscale model reanalysis data. In both cases the model slightly over-predicts the wind speed with differences of 0.25 and 0.40 m s−1, respectively. An important feature in the model-training process is the air–sea temperature difference; thus satellite sea surface temperature observations were included in the horizontal extension of the model, resulting in 0.20 m s−1 differences with NORA3. A limiting factor when training machine-learning models with satellite observations is the small finite number of daily samples at discrete times; this can skew the training process to higher-/lower-wind-speed predictions depending on the average wind speed at the satellite observational times. Nonetheless, results shown in this proof-of-concept study demonstrate the limited applicability of using machine-learning techniques to extrapolate long-term satellite wind observations when enough samples are available.
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France, James L., Prudence Bateson, Pamela Dominutti, Grant Allen, Stephen Andrews, Stephane Bauguitte, Max Coleman, et al. "Facility level measurement of offshore oil and gas installations from a medium-sized airborne platform: method development for quantification and source identification of methane emissions." Atmospheric Measurement Techniques 14, no. 1 (January 5, 2021): 71–88. http://dx.doi.org/10.5194/amt-14-71-2021.
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Abstract. Emissions of methane (CH4) from offshore oil and gas installations are poorly ground-truthed, and quantification relies heavily on the use of emission factors and activity data. As part of the United Nations Climate & Clean Air Coalition (UN CCAC) objective to study and reduce short-lived climate pollutants (SLCPs), a Twin Otter aircraft was used to survey CH4 emissions from UK and Dutch offshore oil and gas installations. The aims of the surveys were to (i) identify installations that are significant CH4 emitters, (ii) separate installation emissions from other emissions using carbon-isotopic fingerprinting and other chemical proxies, (iii) estimate CH4 emission rates, and (iv) improve flux estimation (and sampling) methodologies for rapid quantification of major gas leaks. In this paper, we detail the instrument and aircraft set-up for two campaigns flown in the springs of 2018 and 2019 over the southern North Sea and describe the developments made in both the planning and sampling methodology to maximise the quality and value of the data collected. We present example data collected from both campaigns to demonstrate the challenges encountered during offshore surveys, focussing on the complex meteorology of the marine boundary layer and sampling discrete plumes from an airborne platform. The uncertainties of CH4 flux calculations from measurements under varying boundary layer conditions are considered, as well as recommendations for attribution of sources through either spot sampling for volatile organic compounds (VOCs) ∕ δ13CCH4 or using in situ instrumental data to determine C2H6–CH4 ratios. A series of recommendations for both planning and measurement techniques for future offshore work within marine boundary layers is provided.
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Armstrong, M. A., M. Ravasio, W. G. Versteijlen, D. J. Verschuur, A. V. Metrikine, and K. N. van Dalen. "Seismic inversion of soil damping and stiffness using multichannel analysis of surface wave measurements in the marine environment." Geophysical Journal International 221, no. 2 (February 14, 2020): 1439–49. http://dx.doi.org/10.1093/gji/ggaa080.
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SUMMARY Determination of soil material damping is known to be difficult and uncertain, especially in the offshore environment. Using an advanced inversion methodology based on multichannel spectral analysis, Scholte and Love wave measurements are used to characterize subsea soil from a North Sea site. After normalization, a determinant-based objective function is used in a genetic algorithm optimization to estimate the soil shear modulus. The inverted shear-modulus profile is comparable to previously published results for the same data, although a higher degree of certainty is achieved in the near-surface layers. The half-power bandwidth method is used for extracting the attenuation curve from the measurements and efficient reference data points are chosen based on wavelet compression. The material-damping ratio inversion is performed using a modified stochastic optimization algorithm. Accounting for measurement errors, the material-damping ratio profile is retrieved from the fundamental-mode Scholte wave with a high degree of certainty. Furthermore, a method is proposed for identifying the frequency dependence of the material-damping ratio from in situ measurements. No evidence for frequency dependence is found and the small-strain soil material-damping ratio at this site can be said to be frequency independent for the measured conditions.
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Sun, Miaojun, Zhigang Shan, Wei Wang, Shaopeng Zhang, Heyu Yu, Guangwei Cheng, and Xiaolei Liu. "Development of an Underwater Adaptive Penetration System for In Situ Monitoring of Marine Engineering Geology." Sensors 24, no. 17 (August 28, 2024): 5563. http://dx.doi.org/10.3390/s24175563.
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In recent years, offshore wind farms have frequently encountered engineering geological disasters such as seabed liquefaction and scouring. Consequently, in situ monitoring has become essential for the safe siting, construction, and operation of these installations. Current technologies are hampered by limitations in single-parameter monitoring and insufficient probe-penetration depth, hindering comprehensive multi-parameter dynamic monitoring of seabed sediments. To address these challenges, we propose a foldable multi-sensor probe and establish an underwater adaptive continuous penetration system capable of concurrently measuring seabed elevation changes and sediment pore water pressure profiles. The reliability of the equipment design is confirmed through static analysis of the frame structure and sealed cabin. Furthermore, laboratory tests validate the stability and accuracy of the electrical and mechanical sensor measurements. Preliminary tests conducted in a harbor environment demonstrate the system’s effectiveness.
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Filipot, J. F., P. Guimaraes, F. Leckler, J. Hortsmann, R. Carrasco, E. Leroy, N. Fady, et al. "La Jument lighthouse: a real-scale laboratory for the study of giant waves and their loading on marine structures." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2155 (August 19, 2019): 20190008. http://dx.doi.org/10.1098/rsta.2019.0008.
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This paper presents results from an experiment designed to improve the understanding of the relationship between extreme breaking waves and their mechanical loading on heritage offshore lighthouses. The experiment, conducted at La Jument, an iconic French offshore lighthouse, featured several records of wave, current and structure accelerations acquired during severe storm conditions, with individual waves as high as 24 m. Data analysis focuses on a storm event marked by a strong peak in the horizontal accelerations measured inside La Jument. Thanks to stereo-video wave measurements synchronized to the acceleration record we were able to identify and describe the breaking wave responsible for this intense loading. Our observations suggest that this giant wave (19 m high) had a crest elevation high enough to directly hit the lighthouse tower, above the substructure. This paper reveals the potential for conducting ambitious field experiments from offshore lighthouses in order to collect valuable storm waves and wave loading observations. This offers a possible second service life for these heritage structures as in situ laboratories dedicated to the study of the coastal hydrodynamics and its interaction with marine structures. This article is part of the theme issue ‘Environmental loading of heritage structures’.
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Stuyts, Bruno, Wout Weijtjens, Carlos Sastre Jurado, Christof Devriendt, and Anis Kheffache. "A Critical Review of Cone Penetration Test-Based Correlations for Estimating Small-Strain Shear Modulus in North Sea Soils." Geotechnics 4, no. 2 (June 14, 2024): 604–35. http://dx.doi.org/10.3390/geotechnics4020033.
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The geotechnical characterisation of offshore wind farm sites requires measurement or estimation of the small-strain shear stiffness Gmax of the subsoil. This parameter can be derived from shear wave velocity Vs measurements if the bulk density of the soil is known. Since direct measurements of Vs are generally not available at all foundation locations in a wind farm, correlations with cone penetration test (CPT) results are often used to determine location-specific stiffness parameters for foundation design. Existing correlations have mostly been calibrated to onshore datasets which may not contain the same soil types and stress conditions found in the North Sea. The distinct geological history of the North Sea necessitates a critical review of these existing CPT-based correlations. They are evaluated against an extensive database of in situ Vs measurements in the southern North Sea. The importance of modelling the stress-dependent nature of Vs is highlighted, and a novel stress-dependent model for Vs from CPT data, which leads to an improved fit, is presented. As the small-strain stiffness is used as an input to foundation response calculations, the model uncertainty of the correlation can introduce significant uncertainty into the resulting foundation response. This transformation uncertainty is quantified for each of the correlations evaluated in this study and shows important variations.
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Schmidt, Mark, Peter Linke, and Daniel Esser. "Recent Development in IR Sensor Technology for Monitoring Subsea Methane Discharge." Marine Technology Society Journal 47, no. 3 (May 1, 2013): 27–36. http://dx.doi.org/10.4031/mtsj.47.3.8.
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AbstractRecently developed methane sensors, based on infrared (IR) absorption technology, were successfully utilized for subsea methane release measurements. Long-term investigation of methane emissions (fluid flux determination) from natural methane seeps in the Hikurangi Margin offshore New Zealand were performed by using seafloor lander technology. Small centimeter-sized seep areas could be sampled at the seafloor by video-guided lander deployment. In situ sensor measurements of dissolved methane in seawater could be correlated with methane concentrations measured in discrete water samples after lander recovery. High backscatter flares determined by lander-based Acoustic Doppler Current Profiler (ADCP) measurement indicate bubble release from the seafloor. Highest methane concentrations determined by the IR sensor coincided with periods of high ADCP backscatter signals. The high fluid release cannot be correlated with tidal changes only. However, this correlation is possible with variability in spatial bubble release, sudden outbursts, and tidal changes in more quiescent seepage phases.A recently developed IR sensor (2,000 m depth-rated) with a detection limit for methane of about 1 ppm showed good linearity in the tested concentration range and an acceptable equilibration time of 10 min. The sensor was successfully operated offshore Santa Barbara by a small work-class ROV at a natural methane seep (Farrar Seep). High background methane concentration of 50 nmol L−1 was observed in the coastal water, which increases up to 560 nmol L−1 in dissolved methane plumes south of the seepage area. ROV- and lander-based sensor deployments have proven the applicability of IR sensor technology for the determination of subsea methane release rates and plume distribution. The wide concentration range, low detection limit, and its robust detection unit enable this technology for both subsea leak detection and oceanographic trace gas investigations.
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Wang, Bin, Shan Gao, Yan Qu, Haoyang Yin, and Zhenju Chuang. "Mechanism of Phase-Locked Ice Crushing against Offshore Structures." Journal of Marine Science and Engineering 11, no. 4 (April 20, 2023): 868. http://dx.doi.org/10.3390/jmse11040868.
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This paper addresses a detailed analysis of the ice–structure interaction process of the phase-locked ice crushing (PLC) against offshore structures. Directly measured ice load, structure response data, and in situ observation from the field measurements on the Molikpaq lighthouse and jacket platform were used in the study. This paper summarizes a new ductile damage-collapse (DDC) failure mechanism for the PLC process. The DDC mechanism shows that the ice failure is a discrete ductile crushing process rather than a ductile–brittle transition process. The analysis identifies that the ice has a failure length in PLC and this failure length plays an important role in understanding the interaction. It reveals that PLC can occur on most vertical-sided offshore structures when the velocity of the ice sheet falls within the range of the failure length divided by the natural period of the structure. This paper proposes that this relationship between ice failure length and the natural period of the structure can be used as one of the PLC occurrence conditions. The DDC failure mechanism provides a basis for another technical route to solve the PLC problem.
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Xu, Jingwei, Huanping Wu, Xiefei Zhi, Nikolay V. Koldunov, Xiuzhi Zhang, Ying Xu, Yangyang Zhang, Maohua Guo, Lisha Kong, and Klaus Fraedrich. "Validation of Multisource Altimeter SWH Measurements for Climate Data Analysis in China’s Offshore Waters." Remote Sensing 16, no. 12 (June 14, 2024): 2162. http://dx.doi.org/10.3390/rs16122162.
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Climate data derived from long-term, multisource altimeter significant wave height (SWH) measurements are more valuable than those obtained from a single altimeter source. Such data facilitate exploration of long-term air–sea momentum transfer and more comprehensive investigation of weather system dynamics processes over the ocean. Despite the deployment of the first satellite in the Chinese Haiyang-2 (HY-2) series more than 12 years ago, validation and integration of SWH data from China’s offshore waters, derived using Chinese altimeters, have been limited. This study constructed a high-resolution, long-term, multisource gridded SWH climate dataset using along-track data from the HY-2 series, CFOSAT, Jason-2, Jason-3, and Cryosat-2 altimeters. Validation against observations from 31 buoys covering China’s offshore waters indicated that the SWH variances from HY-2A, HY-2B, HY-2C, CFOSAT, and Jason-3 altimeters correlated well with observations, with a temporal correlation coefficient of approximately 0.95 (except HY-2A, correlation: 0.89). These SWH measurements generally showed a robust linear relationship with the buoy data. Additionally, cross-calibration between Jason-3 and the HY-2A, HY-2B, HY-2C, and CFOSAT altimeters also demonstrated a typically linear relationship for SWH > 6.0 m. Using this relationship, the SWH data were linearly corrected and integrated into a 10 d mean, long-term, multisource altimeter gridded SWH dataset. Compared with in situ observations, the merged 10 d mean SWHs are more accurate and closely match the observations, with temporal correlation coefficients improving from 0.87 to 0.90 and bias decreasing from 0.28 to 0.03 m. The merged gridded SWHs effectively represent the local spatial distribution of SWH. This study revealed the importance of observational data in the process of merging and recalibrating long-term multisource altimeter SWH datasets, particularly before their application in specific ocean regions.
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SOUKISSIAN, T. H., and A. M. PROSPATHOPOULOS. "The Errors-in-Variables approach for the validation of the WAM wave model in the Aegean Sea." Mediterranean Marine Science 7, no. 1 (June 1, 2006): 47. http://dx.doi.org/10.12681/mms.177.
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In previous studies, wave fi elds from the 3rd-generation wave model WAM-Cycle 4 have been validated by using in situ buoy measurements in the Aegean Sea within the framework of the POSEIDON project; however, limitations of the data sets, concerning mainly the short distance of the buoys from the shore and the short length of the data, render those validation studies incomplete. In this work, signifi cant wave height forecasts obtained from WAM-Cycle 4 wave model are validated by means of TOPEX/Poseidon (T/P) data in specifi c offshore locations in the central part of the North Aegean Sea. The linear structural relationship between the two data sets has been modelled by implementing the Error- In-Variables approach, assuming that both T/P data and WAM results are subjected to errors. The underestimation of signifi cant wave height from WAM, which has been concluded from the comparison with buoys at near-shore points, is also observed from the WAM-T/P comparison at offshore locations, thus being considered of general validity for the Aegean Sea. In addition, a correction relation for the WAM model results, based on the linear structural relationship, is proposed and applied.
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Saffer, D. M., P. B. Flemings, D. Boutt, M. L. Doan, T. Ito, L. McNeill, T. Byrne, et al. "In situ stress and pore pressure in the Kumano Forearc Basin, offshore SW Honshu from downhole measurements during riser drilling." Geochemistry, Geophysics, Geosystems 14, no. 5 (May 2013): 1454–70. http://dx.doi.org/10.1002/ggge.20051.
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Morgan, Eugene C., Maarten Vanneste, Isabelle Lecomte, Laurie G. Baise, Oddvar Longva, and Brian McAdoo. "Estimation of free gas saturation from seismic reflection surveys by the genetic algorithm inversion of a P-wave attenuation model." GEOPHYSICS 77, no. 4 (July 1, 2012): R175—R187. http://dx.doi.org/10.1190/geo2011-0291.1.
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Many previously proposed methods of estimating free gas saturation from seismic survey data rely on calibration to invasively collected, in situ measurements. Typically, such in situ measurements are used to parameterize or calibrate rock-physics models, which can then be applied to seismic data to achieve saturation estimates. We tested a technique for achieving estimates of the spatial distribution of gas saturation solely from shipboard seismic surveys. We estimated the quality factor from seismic reflection surveys using the spectral ratio method, and then inverted a mesoscopic-scale P-wave attenuation model to find the parameters that matched the modeled attenuation to our estimates of observed attenuation within the range of seismic frequencies. By using a genetic algorithm for this inversion, we not only searched efficiently for a global solution to the nonlinear set of equations that compose the model, but also constrain the search to a relatively broad set of realistic parameter values. Thus, our estimates do not rely on in situ measurements of these parameters, but on distributions of their possible values, many of which may be referenced from literature. We first tested this method at Blake Ridge, offshore North and South Carolina, where an approximately 400-m-deep gas-saturated zone underlies a field of methane hydrates. The extensive field work and subsequent studies at this site make it ideal for validating our method. We also demonstrated the applicability of our method to shallower deposits by presenting results from Finneidfjord, Norway, where the inversion of the P-wave attenuation model recognizes very small gas saturations.
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Taboada Urtuzuástegui, Víctor Manuel, Francisco Alonso Flores-López, Diego Cruz Roque, Procoro Barrera Nabor, Shuang Cindy Cao Cindy Cao, Kuat C. Gan, Vishal Dantal Dantal, et al. "DYNAMIC PROPERTIES OF SAND FOR EARTHQUAKE RESPONSE ANALYSIS IN THE BAY OF CAMPECHE." Revista de Ingeniería Sísmica, no. 109 (December 30, 2022): 69–91. http://dx.doi.org/10.18867/ris.109.615.
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The Bay of Campeche is located in a region of moderate to high seismic activity related to the active triple junction between the North American, Caribbean, and Cocos plate boundaries. Therefore, the fixed offshore platforms and subsea structures in the Bay of Campeche must be designed against earthquake loading. A database was developed of classification and index properties tests, in situ measurements of shear wave velocity (Vs) using downhole P-S suspension seismic velocity logging, in situ piezocone penetration tests, resonant column tests to characterize the shear modulus and material damping ratio at small shear strains (10−5 % to about 0.1 %), and strain-controlled cyclic direct simple shear tests to evaluate the decrease of shear modulus and the increase of material damping ratio at large shear strains (0.1 % to about 10 %) performed on sand from the Bay of Campeche, including sands with no carbonate content to 100 % carbonate content, retrieved from the seafloor to a penetration depth of 120 m below seafloor. The database was tailored specifically to develop empirical correlations for the Bay of Campeche sand to determine Vs when in situ measurements of Vs are not available and to develop numerical modeling to predict the variation of the normalized shear modulus (G/Gmax) and material damping ratio (D) as a function of shear strains (g) when dynamic test results are unavailable for all the sand layers. The equations developed to calculate Vs and the curves of G/Gmax-g and D-g of Bay of Campeche sands are recommended for preliminary or perhaps even final seismic site response evaluations.
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Taboada Urtuzuástegui, Víctor Manuel, Shuang Cindy Cao, Diego Cruz Roque, Francisco Alonso Flores-López, Prócoro Barrera, Kuat C. Gan, Vishal Dantal, Esteban Ernesto Espinosa Samudio, Sergio Dionicio Renovato Carrión, and Juan Manuel Hernández Durón. "DYNAMIC PROPERTIES OF CLAY FOR EARTHQUAKE RESPONSE ANALYSIS IN THE BAY OF CAMPECHE." Revista de Ingeniería Sísmica, no. 109 (December 30, 2022): 47–68. http://dx.doi.org/10.18867/ris.109.596.
Full textAbstract:
The Bay of Campeche is located in a region of moderate to high seismic activity related to the active triple junction between the North American, Caribbean, and Cocos plate boundaries. Therefore, the fixed offshore platforms and subsea structures in the Bay of Campeche must be designed against earthquake loading. A database was developed of classification and index properties tests, in situ measurements of shear wave velocity using downhole P-S suspension seismic velocity logging, in situ piezocone penetration tests, resonant column tests to characterize the shear modulus and material damping ratio at small shear strains (10−5 % to about 0.1 %), and strain-controlled cyclic direct simple shear tests to evaluate the decrease of shear modulus and the increase of material damping ratio at large shear strains (0.1 % to about 10 %) performed on clays from the Bay of Campeche, including clays with no carbonate content to 100 % carbonate content, retrieved from the seafloor to a penetration depth of 120 m below seafloor. The database was tailored specifically to develop empirical correlations for the Bay of Campeche clay to determine Vs when in situ measurements of Vs are not available and to develop numerical modeling to predict the variation of the normalized shear modulus (G/Gmax) and material damping ratio as a function of shear strains (g) when dynamic test results are unavailable for all the clay layers. The equations developed to calculate Vs and the curves of G/Gmax-g and D-g of Bay of Campeche clays are recommended for preliminary or perhaps even final seismic site response evaluations.
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Sanada, Yukihisa, Kenji Miyamoto, Hiroyasu Momma, Nobuyuki Miyazaki, Takamasa Nakasone, Junichiro Tahara, Shoichiro Baba, and Hiroki Furuyama. "Development of a Radiation Survey Device for a Multipurpose Unmanned Surface Vehicle." Marine Technology Society Journal 55, no. 5 (September 1, 2021): 222–30. http://dx.doi.org/10.4031/mtsj.55.5.19.
Full textAbstract:
Abstract Large quantities of volatile radionuclides were released into the atmosphere after the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. An inventory of these radionuclides in seafloor sediments is important for evaluating their environmental behavior and effects on aquatic organisms. We developed a dedicated radiation survey device that can be installed on a multipurpose unmanned surface vehicle called the Intelligent Boat for Oceanological Survey from Hama-dori (i-BoSH). Both the i-BoSH and dedicated radiation survey device were developed by a local consortium to survey places of heavy damage from the accident. The radiation survey device can measure radioactivity in-situ and collect eight sediment samples. The device also contains sensors to measure the relative distance between the i-BoSH and the seafloor as well as other fundamental seawater information such as temperature. A comprehensive test that included in-situ radiation measurements in sediment and collection of sediment core samples was conducted offshore from a radiocesium-contaminated fishing port in Fukushima. Consequently, the effectiveness of this device was confirmed via a successful operation at 12 sampling points with two cruises from the fishing port. Good correlations were observed between the laboratory and field measurement results of the sampled sediment cores and the in-situ radiation survey, respectively. Successful application of this device is expected to go beyond environmental surveys around the FDNPS to more general radiation monitoring around nuclear facilities and longer post-accident periods.
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Osadchiev, Alexander, Roman Sedakov, Alexandra Gordey, and Alexandra Barymova. "Internal Waves as a Source of Concentric Rings within Small River Plumes." Remote Sensing 13, no. 21 (October 24, 2021): 4275. http://dx.doi.org/10.3390/rs13214275.
Full textAbstract:
This study is focused on concentric rings, which are regularly observed by remote sensing of small river plumes located in different regions worldwide. We report new aerial observations of these features obtained by quadcopters and supported by synchronous in situ measurements, which were collected during the recent field survey at the Bzyb river plume in the eastern part of the Black Sea. Joint analysis of remote sensing imagery and in situ data suggest that the observed concentric rings are surface manifestations of high-frequency internal waves generated in the vicinity of the river mouth. The obtained results demonstrate that the propagation of these waves does not induce offshore material transport within the plume induced by shear instability, which was hypothesized in a recent numerical modeling study of this process. We provide an explanation for the appearance of misleading material features in the numerical simulations discussed above. Finally, we discuss directions for future research of high-frequency internal waves generated in small river plumes.
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Raileanu, Alina, Florin Onea, and Liliana Rusu. "Coastal protection of the Romanian nearshore throughout hybrid wave and offshore wind farms." E3S Web of Conferences 51 (2018): 01004. http://dx.doi.org/10.1051/e3scconf/20185101004.
Full textAbstract:
The objective of the present work is to estimate the influence of several hybrid wind and wave farm configurations on the wave conditions reported in the vicinity of the Saint George coastal area, in the Romanian nearshore of the Black Sea. Based on the wave data coming from a climatological database (ERA20C) and also on in situ measurements, it was possible to identify the most relevant wave patterns, which will be further considered for assessment. The numerical simulations were carried out with the SWAN (Simulating Waves Nearshore) wave model, which may provide a comprehensive picture of the wave transformation in the presence of the marine farms. Although the impact of the wind farm is not visible from the spatial maps, from the analysis of the values corresponding to the reference points, it was noticed that a maximum variation of 2% may occur for several wave parameters.
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Raileanu, Alina, Florin Onea, and Liliana Rusu. "Coastal protection of the Romanian nearshore throughout hybrid wave and offshore wind farms." E3S Web of Conferences 51 (2018): 01004. http://dx.doi.org/10.1051/e3sconf/20185101004.
Full textAbstract:
The objective of the present work is to estimate the influence of several hybrid wind and wave farm configurations on the wave conditions reported in the vicinity of the Saint George coastal area, in the Romanian nearshore of the Black Sea. Based on the wave data coming from a climatological database (ERA20C) and also on in situ measurements, it was possible to identify the most relevant wave patterns, which will be further considered for assessment. The numerical simulations were carried out with the SWAN (Simulating Waves Nearshore) wave model, which may provide a comprehensive picture of the wave transformation in the presence of the marine farms. Although the impact of the wind farm is not visible from the spatial maps, from the analysis of the values corresponding to the reference points, it was noticed that a maximum variation of 2% may occur for several wave parameters.
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Menon, Harilal B., Nutan Sangekar, Aneesh Lotliker, Krishnaswamy Krishna Moorthy, and Ponnumani Vethamony. "Aerosol optical thickness and spatial variability along coastal and offshore waters of the eastern Arabian Sea." ICES Journal of Marine Science 68, no. 4 (January 10, 2011): 745–50. http://dx.doi.org/10.1093/icesjms/fsq191.
Full textAbstract:
Abstract Menon, H. B., Sangekar, N., Lotliker, A., Krishna Moorthy, K., and Vethamony, P. 2011. Aerosol optical thickness and spatial variability along coastal and offshore waters of the eastern Arabian Sea. – ICES Journal of Marine Science, 68: 745–750. Data from the ocean-colour monitor (OCM) on board the Indian Remote Sensing Satellite P4 were used to analyse the spatial and temporal distribution of aerosol optical thickness (AOT) over the coastal and offshore waters of the eastern Arabian Sea. Zero water-leaving radiance from the near infrared (NIR) region was assumed for oceanic (open ocean) waters, because of the absorption of long-wave radiation by water molecules. As this assumption fails in coastal waters, it was necessary to correct for water-leaving radiance and sun glint to the NIR bands. The aerosol size-distribution parameter (α) was derived from a relationship between two NIR bands. The Ångström turbidity parameter (β) was obtained using an algorithm relating in situ hand-held, sun-photometer measurements and aerosol radiance (La) at 490 nm. The relationship between β and La (490) was derived with a sensitivity analysis, using a calibrated radiative transfer model. AOTs were retrieved for each pixel of 500 nm. The algorithm's performance was tested by comparing OCM-derived AOT values with in situ AOT and MODIS-derived values. Aerosol maps thus generated from January to December 2005 demonstrate the potential of this new retrieval method for producing AOT climatology from OCM data over coastal waters.