Analysis of wave energy distribution in the Gulf of Guinea based on reanalysis data from 1993 to 2019

Surface current velocities of mesoscale eddies have a unique annular structure, which can inevitably influence surface wave properties and energy distribution. Sensitivity experiments of ideal mesoscale eddies on waves were carried out by the Simulating WAves Nearshore (SWAN) wave model to investigate these influences. In addition, China–France Oceanography SATellite Surface Wave Investigation and Monitoring (CFOSAT-SWIM) observational data of a large warm-cored eddy in the South China Sea (SCS) during the period of October–November 2019 were used to validate the influence of mesoscale eddies on waves. The results illustrated that mesoscale eddies can alter wave properties (wave height, period, and steepness) by 20–30%. Moreover, wave direction could also be modified by 30°–40°. The current effect on waves (CEW) was more noticeable with strong currents and weak winds, and was governed by wave age and the ratio of wave group velocity to current velocity. Wave spectra clearly indicated that current-induced variability in wave energy distribution happens on a spatial scale of 5–90 km (i.e., the sub- and mesoscales). Through comparing the difference of wave energy on both sides of an eddy perpendicular to the wave propagation direction in an eddy, a simple way to trace the footprints of waves on eddies was devised.

Long-range horizontal and local vertical transport of biomass burning ozone precursors (i.e. carbon monoxide and nitrogen oxides) from Central Africa are simulated for June 2006. Twenty-kilometer resolution combined meteorological and chemical simulations examine transport pathways, spatial distribution, and quantities of ozone precursors and ozone. Results suggest that due to biomass burning, ozone mixing ratios increase by 28–33 parts per billion by volume in the lower troposphere (850 hecto-Pascals) over the Atlantic Ocean west of Central Africa during June. The inter-hemispheric transport of biomass burning emissions from Central Africa subsides over the Gulf of Guinea with a northward extent of approximately 2–5°N. In the lower troposphere, ozone mixing ratio increases decrease from 28 parts per billion by volume in the southern Gulf of Guinea to 2–3 parts per billion by volume on the Gulf of Guinea Coast. There is middle and upper tropospheric ozone enhancement of 6–12 parts per billion over the Equatorial Atlantic Ocean which is the result of convective detrainment of ozone precursors from deep convection on the Gulf of Guinea Coast followed by transport that propagates around a broad anticyclone. The model ozone produced by biomass burning emissions is less than the observed implying that lightning-induced nitrogen oxide emissions, which are not included in this simulation, are a significant tropospheric ozone source for the eastern Equatorial Atlantic Ocean.

Wave energy resources are abundant in both offshore and nearshore areas of the China’s seas. A reliable assessment of the wave energy resources must be performed before they can be exploited. First, for a water depth in offshore waters of China, a parameterized wave power density model that considers the effects of the water depth is introduced to improve the calculating accuracy of the wave power density. Second, wave heights and wind speeds on the surface of the China’s seas are retrieved from an AVISO multi-satellite altimeter data set for the period from 2009 to 2013. Three mean wave period inversion models are developed and used to calculate the wave energy period. Third, a practical application value for developing the wave energy is analyzed based on buoy data. Finally, the wave power density is then calculated using the wave field data. Using the distribution of wave power density, the energy level frequency, the time variability indexes, the total wave energy and the distribution of total wave energy density according to a wave state, the offshore wave energy in the China’s seas is assessed. The results show that the areas of abundant and stable wave energy are primarily located in the north-central part of the South China Sea, the Luzon Strait, southeast of Taiwan in the China’s seas; the wave power density values in these areas are approximately 14.0–18.5 kW/m. The wave energy in the China’s seas presents obvious seasonal variations and optimal seasons for a wave energy utilization are in winter and autumn. Except for very coastal waters, in other sea areas in the China’s seas, the energy is primarily from the wave state with 0.5 m ⩽ H s ⩽ 4 m, 4 s ⩽ T e ⩽ 10 s where H s is a significant wave height and T e is an energy period; within this wave state, the wave energy accounts for 80% above of the total wave energy. This characteristic is advantageous to designing wave energy convertors (WECs). The practical application value of the wave energy is higher which can be as an effective supplement for an energy consumption in some areas. The above results are consistent with the wave model which indicates fully that this new microwave remote sensing method altimeter is effective and feasible for the wave energy assessment.

Wave energy resources assessment is a very important process before the exploitation and utilization of the wave energy. At present, the existing wave energy assessment is focused on theoretical wave energy conditions for interesting areas. While the evaluation for exploitable wave energy conditions is scarcely ever performed. Generally speaking, the wave energy are non-exploitable under a high sea state and a lower sea state which must be ignored when assessing wave energy. Aiming at this situation, a case study of the East China Sea and the South China Sea is performed. First, a division basis between the theoretical wave energy and the exploitable wave energy is studied. Next, based on recent 20 a ERA-Interim wave field data, some indexes including the spatial and temporal distribution of wave power density, a wave energy exploitable ratio, a wave energy level, a wave energy stability, a total wave energy density, the seasonal variation of the total wave energy and a high sea condition frequency are calculated. And then the theoretical wave energy and the exploitable wave energy are compared each other; the distributions of the exploitable wave energy are assessed and a regional division for exploitable wave energy resources is carried out; the influence of the high sea state is evaluated. The results show that considering collapsing force of the high sea state and the utilization efficiency for wave energy, it is determined that the energy by wave with a significant wave height being not less 1 m or not greater than 4 m is the exploitable wave energy. Compared with the theoretical wave energy, the average wave power density, energy level, total wave energy density and total wave energy of the exploitable wave energy decrease obviously and the stability enhances somewhat. Pronounced differences between the theoretical wave energy and the exploitable wave energy are present. In the East China Sea and the South China Sea, the areas of an abundant and stable exploitable wave energy are primarily located in the north-central part of the South China Sea, the Luzon Strait, east of Taiwan, China and north of Ryukyu Islands; annual average exploitable wave power density values in these areas are approximately 10–15 kW/m; the exploitable coefficient of variation (COV) and seasonal variation (SV) values in these areas are less than 1.2 and 1, respectively. Some coastal areas of the Beibu Gulf, the Changjiang Estuary, the Hangzhou Bay and the Zhujiang Estuary are the poor areas of the wave energy. The areas of the high wave energy exploitable ratio is primarily in nearshore waters. The influence of the high sea state for the wave energy in nearshore waters is less than that in offshore waters. In the areas of the abundant wave energy, the influence of the high sea state for the wave energy is prominent and the utilization of wave energy is relatively difficult. The developed evaluation method may give some references for an exploitable wave energy assessment and is valuable for practical applications.

Prediction of wave energy distribution in coastal areas is necessary if an assessment of the likelihood of cliff collapse is to be undertaken. Use has been made of numerical modelling to predict relative wave heights along the chalk cliff coastline of East Sussex between Brighton and Eastbourne, UK. In this study, wave modelling has been undertaken using the University of Delaware REFDIF-1 software with a 100m mesh size to predict nearshore wave heights for boundary unit wave height conditions from a range of different incident directions. The results from this wave modelling have been combined with the frequency distribution of incident waves obtained from analysis of time series of 12 years of hindcast wave data in the English Channel, obtained from the UK Meteorological Office. The resulting distribution of nearshore wave heights is presented as a surrogate for the distribution of wave energy over the 12-year period. Some concern exists about the quality of the output data, in particular of the effect of the relatively coarse bathymetry grid used for the model. Some wave focusing is evident from the model output, caused by the presence of local shoals in the model grid, leading to a ‘banding’ effect in the model output. Some suggestions are made for the improvement of the modelling scheme, including the use of finer mesh size, bathymetric smoothing and the use of a spectral model such as REFDIF-S.

The Gulf of Guinea coast is a region endowed with petroleum resources and this has brought prominence to the region as major oil consumers and oil companies are found in the region. The region has become an alternative source of energy to the Middle East and demand for the region’s oil has continued to increase. Different countries make up the Gulf of Guinea with different colonial background, economic interest and levels of suspicion. This paper examines relations among these countries and its implication on their oil endowment and security. It suggests efforts that the Gulf of Guinea states can make to strengthen relations/cooperation among these states as this will enhance economic the development of the Gulf of Guinea coast.

Surface wave energy and dissipation are observed across the surf zone. Utilizing the concept of surface rollers, a new scaling is introduced to obtain the energy flux and dissipation related to rollers from Doppler velocities measured by a shore‐based X‐band marine radar. The dissipation of wave energy and hence the transformation of the incoming wave height (or energy) is derived using the coupled wave and roller energy balance equations. Results are compared to in‐situ wave measurements obtained from a wave rider buoy and two bottom mounted pressure wave gauges. A good performance in reproducing the significant wave height is found yielding an overall root‐mean‐square error of 0.22 m and a bias of −0.12 m. This is comparable to the skill of numerical wave models. In contrast to wave models, however, the radar observations of the wave and roller energy flux and dissipation neither require knowledge of the bathymetry nor the incident wave height. Along a 1.5 km long cross‐shore transect on a double‐barred, sandy beach in the southern North Sea, the highest dissipation rates are observed at the inner bar over a relatively short distance of less than 100 m. During the peak of a medium‐severe storm event with significant wave heights over 3 m, about 50% of the incident wave energy flux is dissipated at the outer bar.

The concentrations of natural radionuclides in the sediments along the Lagos coast and the Gulf of Guinea in South-western Nigeria were measured using gamma-ray spectrometry. The mean activity concentrations of40K,238U, and232Thwere found to vary, with values of 240.36 ± 129.90 Bqkg-1, 6.20 ± 1.08 Bqkg-1, and 4.26 ± 1.40 Bqkg-1 at the Lagos coast, and 432.50 ± 68.18 Bqkg-1, 10.76 ± 2.96 Bqkg-1, and 3.85 ± 1.82 Bqkg-1 at the Gulf of Guinea coast, respectively. The overall calculated mean of the indoor absorbed dose rates was 17.58 ± 5.66 nGyh-1, with a corresponding total annual effective dose of 0.11 ± 0.03 mSvy-1. To assess the radiological hazards associated with the presence of naturally occurring radioactive materials (NORM) in sediments, we calculated the representative level index (RLI), radium equivalent activity (Raeq), external hazard index (Hex), excess lifetime cancer risk (ELCR), and internal hazard index (Hin). These indices provide a way to evaluate potential health risks to humans, benthic ecosystems, and the marine environment. The overall estimated values for Raeq, Hex, Hin, RLI, and ELCR were 31.10 ± 12.32 Bqkg-1, 0.08 ± 0.03, 0.10 ± 0.04, 0.28 ± 0.09, and 0.07 ± 0.03 × 10-3, respectively. Principal Component Analysis (PCA) was used to link radionuclide distributions to sediment's particle size, and results reveal close association between sand and silt with elevated 232Th; and clay with enriched 40K and 238U concentrations respectively. The sediment values from the Lagos coast and the Gulf of Guinea fell below the safety limits set by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (e.g., 400Bqkg-1, 30Bqkg-1 and 35Bqkg-1), except at few stations that showed elevated 40K due to local geology. The values obtained for the hazard indices in sediment from the study area were similar to those found in other areas recognized for their low radiation levels. Therefore, it can be concluded that sediments from the Lagos coasts and Gulf of Guinea basins pose minimal potential health risks to humans, benthic ecosystems, and the environment, complying with established guidelines and regulations for permissible radiation exposure. The results of this study could serve as an important baseline for future epidemiological studies and monitoring initiatives in the region.

The interest in harnessing the wave energy resource has been reflected in a large number of assessments of this resource around the world. These are aimed at the installation of wave energy converters and thus contribute to the expansion of the energy matrix and the reduction of greenhouse gas emissions. The evaluations of the energy resources of the marine waves have been developed through characterizations that use data from measurements, and numerical simulations carried out near the coasts of various countries. There is scarce research on wave energy resources in places with an open ocean configuration like Peru Basin. We point out that wave energy in Peru Basin is intensive in quantity and direction to make the deployment of WECs profitable. This paper aims to assess wave energy resources in Peru Basin. A wave spectrum theory and numerical methods are used. High-quality data for 11 years were used. Wave energy is concentrated in a narrow band of wave heights and energy periods. Wave energy corresponds to high wave power. Wave power direction is strong about southwest.

The coastline of the African Gulf of Guinea hosts large river deltas, coastal wetlands and mangrove ecosystems. It is in places densely populated, with many capital megacities with millions of inhabitants such as Lagos, Abidjan and Accra situated at the coast. And population projections for these cities suggest a continued staggering increase in the coming decades. Also, many of the economic activities are located along the coastline. For example, Nigerian coastal areas are home to 85% of the nation industry and to more than 100 million people. On the other hand, the coastland retains pristine transitional environments formed during the Holocene, well recognized for the great biological richness and the high level of endemism. These pressures and foreseen growth make these lowly elevated coastal areas particularly vulnerable to relative sea-level rise (SLR).Regional or local impact studies of climate-change induced global sea-level rise are scarce and, when available, do not account for vertical land motion, i.e. land subsidence. Coastal land subsidence is critically under-quantified at global scale and the Gulf of Guinea region is no exception to this. Meanwhile, examples elsewhere in the World show coastal economic development and population growth can accelerate land subsidence to rates that are magnitudes larger than global SLR. With the fast-paced developments taking place along the Gulf of Guinea’s coastline, land subsidence poses an unknown but potentially large hazard to this region.Here, we present the first findings in our work to assess coastal subsidence in this fast-changing region of the World, through regional and local case studies and satellite assessments. By building on the recent advancements in global elevation data, we aim to update coastal elevation estimates and identify low lying hotspots with high vulnerability to relative SLR. Ultimately, we aim to project coastal elevation change for this important region and, in case of human-induced land subsidence, show how much relative SLR can potentially be avoided by changing to sustainable use of natural resources. Hence, we may be able to alter the fate of deltas, wetlands and coastal cities by quantifying and addressing land subsidence as early as in this fast growing region of the world.

According to earlier estimates, the Russian coasts have a high potential of wave and wind energy. At the same time, the use of several types of renewable energy sources (RES) allows us to overcome the inherent drawback–the inhomogeneity in time of the energy flow. Nowadays in Russia and abroad, the results of satellite observations, mathematical modeling and reanalysis data are widely used to assess the potential of wind and wave resources. The maps, the atlases, the databases and other information resources (both printed and electronic) are developed for use in the design, mathematical modeling of the power plants performance on the base of RES including hybrid ones. The paper presents the results of developing a Web Atlas of wave and wind energy for the coastal zone of the seas in the Russian Federation, demonstrates the methods for calculating wave and wind characteristics (SWAN spectral wave model), as well as data sources (wind speed reanalyses NCEP / CFSR and NCEP / CFSv2 for the periods 19792010 and 2011-2016). As the characteristics of the energy potential, mean annual values of the height of significant waves, length, period of waves, flux of wave energy, average specific power of the wind flow are calculated and analyzed. The tools for developing a Web Atlas prototype are discussed in detail. Web Atlas is based on the classical three-tier model which includes a storage subsystem (database server), a subsystem for analyzing and publishing data (directly a GIS server), and a Web application subsystem providing a user interface for interacting with data and mapping services (web server). The implementation of the Web Atlas has been carried out for the Black Sea waters. It is planned to further develop the atlas covering the coastal waters of all the seas of Russia.

The computer model COREEF was used to simulate variations in the zonation patterns of Caribbean reefs in relation to parameters that affect the magnitude and distribution of wave and light energy. We first developed a simulated standard reef by exposing a simplified profile of the reef at Discovery Bay, Jamaica, to the known wave and light energy conditions to establish a reference coralgal and sedimentological zonation pattern. We then varied 13 parameters related to the wave and light energy input, bathymetric setting, and gross morphology of this reef to determine the effects of each parameter on the zonation pattern. Analysis of the simulation results indicates that submerging the reef or altering the wave or light energy input to the reef produces the greatest modifications of the zonation pattern. Morphological structures that alter a reef's horizontal dimensions only minimally affect the zonation pattern, but those structures that alter a reef's vertical dimensions-particularly steep-sided, wave reflecting structures-can significantly modify the zonation of the structure itself and that of more leeward areas. The more seaward the location of a morphological structure, the more profoundly it can affect the overall reef zonation. If waves break at the reef crest, wave energy conditions in the back reef are greatly reduced and the bottom consists of lower wave energy zones than those found at the same depths in the fore reef. If waves do not break at the crest, the back reef is subjected to almost the same wave conditions that exist in the fore reef, and the zones tend to be similar. The zonation patterns of some existing reefs resemble those of our simulated reefs, but other zonation patterns cannot be reproduced accurately because our simulation experiments do not consider the interactions between multiple parameters found on many existing reefs.

Global efforts to reduce reliance on fossil fuels and greenhouse gas emissions increasingly emphasize the potential of marine energy as a renewable resource. This study analyzes the characteristics of significant wave height and estimates of wave energy and wave power in the northern waters of Central Java, Indonesia, during 2024. ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) were processed using Python to generate monthly maps of wave height and wave energy, daily time series of energy and power, and boxplots of monthly wave-energy distribution. The annual significant wave height ranged from 0.1 to 1.6 m, with the highest values occurring in December and March and the lowest in April and November. Monthly wave energy exceeded 1,200 J m⁻², while daily wave-energy density reached up to 3,000 J m⁻² and daily wave power peaked near 6 kW m⁻¹ during the west monsoon season. The highest variability occurred in March and December, reflecting the influence of monsoonal wind forcing. These findings demonstrate that the northern Central Java Sea has promising, relatively stable wave-energy potential, particularly during the west monsoon. They may contribute to Indonesia’s clean-energy transition, coastal resilience, and small-island electrification, in alignment with Sustainable Development Goals 7 and 13.

The West Africa monsoon precipitation of the ECMWF operational Seasonal Forecast System (SYS3) is evaluated at a lead time of 2–4 months in a 49-yr hindcast dataset, with special attention paid to the African Monsoon Multidisciplinary Analysis (AMMA) special observation period during 2006. In both the climatology and the year 2006 the SYS3 reproduces the progression of the West Africa monsoon but with a number of differences, most notably a southerly shift of the precipitation in the main monsoon months of July and August and the lack of preonset rainfall suppression and sudden onset jump. The model skill at predicting summer monsoon rainfall anomalies has increased in recent years indicating improvements in the ocean analysis since the 1990s. Examination of other model fields shows a widespread warm sea surface temperature (SST) bias exceeding 1.5 K in the Gulf of Guinea throughout the monsoon months in addition to a cold bias in the North Atlantic, which would both tend to enhance rainfall over the Gulf of Guinea coast at the expense of the monsoon rainfall over the Sahel. Seasonal forecasts were repeated for 2006 using the same release of the atmospheric forecast model forced by observed SSTs, and the monsoon rainfall reverts to its observed position, indicating the importance of the SST biases. A lack of stratocumulus off the west coast of Africa in SYS3 was hypothesized as a possible cause of the systematic rain and SST biases. Two more sets of ensembles were thus conducted with atmospheric model upgrades designed to tackle radiation, deep convection, and turbulence deficiencies. While these enhancements improve the simulation of stratocumulus significantly, it is found that the improvement in the warm SST bias is limited in scope to the southern cold tongue region. In contrast, the changes to the representation of convection cause an increase in surface downwelling shortwave radiation that, combined with latent heat flux changes associated with the wind stress field, increases the SST warm bias on and to the north of the equator. Thus, while the precipitation shortfall in the Sahel is reduced with the new physics, the overestimated rainfall of SYS3 in the coastal region is further enhanced, degrading the model systematic errors overall in the West Africa region. Finally, the difference in the systematic biases between the coupled and uncoupled systems was noted to be an impediment to the development of seamless forecasting systems.

Objectives/Scope Wave resource characterization is a critical step for wave energy converter deployment in the coastal ocean and relies on long-term, high-resolution wave datasets. This study presents a detailed modeling study of the wave resource along the U.S. West Coast (Washington, Oregon, and California), a coastal region that was identified with high wave energy potential in earlier studies. Methods, Procedures, Process The wave hindcast covers a 32-year period from 1979 to 2010 and is based on a multi-resolution, unstructured-grid SWAN model framework. Model configuration closely follows and meets the requirements recommended by the International Electrotechnical Commission Technical Specification (IEC TS) for wave energy resource assessment and characterization (Class 2 - feasibility study). The model domain covers the entire U.S. Exclusive Economic Zone (EEZ) in the West Coast and has a spatial resolution varying from ~300 m in the nearshore region (20 km from the shoreline) to ~2500 m within the EEZ and ~5000 m at the open boundary, which extends beyond the EEZ. The model was forced by hourly 2-D wave spectra produced by a two-way nested WaveWatch III model, which covers the global ocean domain and the broader U.S. West Coast region domain with spatial resolutions of 0.5 degree and 10 arc-minutes, respectively. Both wave models are forced by hourly, 0.5-degree wind forcing obtained from NCEP's Climate Forecast System Reanalysis (CFSR) product. Results, Observations, Conclusions The standard model output for the SWAN model includes 3-hourly output for the six IEC wave resource parameters (e.g., omnidirectional wave power) at each grid point and hourly 2-D spectra at more than 50 NDBC buoys. Extensive model validation was achieved by comparing the six model-predicted IEC parameters with those derived from field observations at representative NDBC buoys. The error statistics indicated the model's satisfactory performance. Further analyses were conducted to systematically evaluate the temporal and spatial distributions of wave energy potential and wave climate along the U.S. West Coast. Results suggest that Washington and Oregon coasts have similar nearshore wave resource, which is significantly higher than resources in Southern California. Strong seasonal variations are also observed, e.g., high wave energy tends to occur in the winter months. In summary, this study produced the first high-resolution, comprehensive dataset on wave energy distribution along the U.S. West Coast. Novel/Additive Information The results are being used by the National Renewable Energy Laboratory to update the MHK Atlas, which was originally derived from NOAA's 4-arc-minute WaveWatch III model output. In addition, the monthly averaged wave energy climatology dataset can be readily shared to support a variety of research and application efforts within the EEZ of the U.S. West Coast.