Modelling Long-Term Trends in Significant Wave Height and its Potential Impacts on Ship Structural Loads

2013 ◽  
Author(s):  
Erik Vanem ◽  
Elzbieta M. Bitner-Gregersen
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Ocean Wave ◽  
Future Trends ◽  
Significant Wave ◽  
Long Term Trends ◽  
Ocean Wave Climate ◽  
The Impact

This paper presents the results from a statistical model for significant wave height in space and time. In particular, various model alternatives were applied to extract long-term temporal trends towards the year 2100. Future projections of the North Atlantic ocean wave climate based on two of these alternatives are presented, i.e. an extrapolated linear trend and trends based on regression on atmospheric levels of CO2 and assuming future emission scenarios proposed by IPCC. It is further explored how such future trends can be related to the structural load calculations of ships. It will be demonstrated how the estimated future trends can be incorporated in joint environmental models to yield updated environmental contour lines that take possible changes in the ocean wave climate into account. In this way, the impact of climate change on the wave climate can be accounted for in stress and loads calculations and hence in the structural dimensioning of ships and offshore installations. The proposed approach is illustrated by an example showing the potential impact of the estimated long-term trends in the wave climate on the wave-induced structural loads of an oil tanker. Results indicate that the impact may be far from negligible, and that this may need to be considered in the future when performing loads calculations.

Time Series Analysis of Significant Wave Height Data for Identification of Trends in the Ocean Wave Climate

2013 ◽  
Author(s):  
Erik Vanem ◽  
Sam-Erik Walker
Keyword(s):  
Time Series ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Ocean Wave ◽  
Significant Wave ◽  
Long Time ◽  
Long Term Trends ◽  
Ocean Wave Climate

Reliable return period estimates of sea state parameters such as the significant wave height is of great importance in marine structural design and ocean engineering. Hence, time series of significant wave height have been extensively studied in recent years. However, with the possibility of an ongoing change in the global climate, this might influence the ocean wave climate as well and it would be of great interest to analyze long time series to see if any long-term trends can be detected. In this paper, long time series of significant wave height stemming from the ERA-40 reanalysis project, containing 6-hourly data over a period of more than 44 years are investigated with the purpose of identifying long term trends. Different time series analysis methods are employed, i.e. seasonal ARIMA, multiple linear regression, the Theil-Sen estimator and generalized additive models, and the results are discussed. These results are then compared to previous studies; in particular results are compared to a recent study where a spatio-temporal stochastic model was applied to the same data. However, in the current analysis, the spatial dimension has been reduced and spatial minima, mean and maxima have been analysed for temporal trends. Overall, increasing trends in the wave climate have been identified by most of the modelling approaches explored in the paper, although some of the trends are not statistically significant at the 95% level. Based on the results presented in this paper, it may be argued that there is evidence of a roughening trend in the recent ocean wave climate, and more detailed analyses of individual months and seasons indicate that these trends might be mostly due to trends during the winter months.

Monthly Variations of Global Wave Climate due to Global Warming

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
Muhammad Zikra ◽  
Noriaki Hashimoto ◽  
Kodama Mitsuyasu ◽  
Kriyo Sambodho
Keyword(s):  
Global Warming ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Ocean Wave ◽  
Climate Data ◽  
Significant Wave ◽  
Wide Range ◽  
Wind Climate ◽  
Ocean Wave Climate

Over recent years, ocean wave climate change due to global warming has attracted a lot of attention not only coastal and offshore engineer but also stakeholders in the marine industry. There is a wide range of application in ocean environment that require information on ocean wave climate data, such as ships design, design of offshore platforms and coastal structures or naval industry. In this research, monthly variation in significant wave height is studied using MRI-AGCM3.2 wind climate data for 25 year period from 1979-2003. The 25 year significant wave height simulation derived from JMA/MRI-AGCM wind climate data. The JMA/MRI-AGCM climate data were input into WAM model. The results showed that the monthly variability of significant wave height in the Northern Hemisphere is greater than in the Southern Hemisphere. Meanwhile, most of the equatorial regions are in calm condition all year. 

scholarly journals Variations in Winter Ocean Wave Climate in the Japan Sea under the Global Warming Condition

2019 ◽  
Vol 7 (5) ◽  
pp. 150 ◽  
Author(s):  
Kenji Taniguchi
Keyword(s):  
Global Warming ◽  
Wave Height ◽  
Significant Wave Height ◽  
Japan Sea ◽  
Wave Climate ◽  
Ocean Wave ◽  
Significant Wave ◽  
The Japan Sea ◽  
Ocean Wave Climate ◽  
Daily Wave

Future variations in the ocean wave climate caused by global warming could affect various coastal issues. Using a third-generation wave model, this study produced projections of the ocean wave climate for winter around Japan, focusing on the Japan Sea side. Wave simulation forcing (sea surface wind) was generated through five different global warming experiments. More than half the future wave projections showed an increasing tendency of the climatological mean significant wave height during winter. However, the maximum significant wave height did not show any clear tendency in future variation. The top 1% of significant wave heights and mean wave periods showed apparent increases in frequencies of higher/longer waves in three out of the five future projections. Frequency distributions of significant wave height, mean wave period, mean wavelength and wave direction showed various future variations (reduction of small ocean waves, increasing frequency of waves from the west). There are large uncertainties in future variations of wave climate in the Japan Sea, but the high probability of variations in daily wave climate is recognized, based on the future wave projections. Variations in daily wave climate are important because they could affect the topography and environment of the coast through long-term repetitive actions.

Seasonally Variation of Significant Wave Height for 25 Year Period Based on JMA/MRI-AGCM3.2 Wind Climate Data

2017 ◽  
Vol 862 ◽  
pp. 67-71
Author(s):  
Muhammad Zikra ◽  
Noriaki Hashimoto ◽  
Kodama Mitsuyasu ◽  
Trika Pitana ◽  
Silvianita
Keyword(s):  
Global Warming ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Ocean Wave ◽  
Climate Data ◽  
Significant Wave ◽  
Wave Data ◽  
Wind Climate ◽  
Ocean Wave Climate

The global ocean wave climate has long been of interest to the ocean engineering community because of the need for accurate operational wave data for applications such as vessel design, design of offshore and coastal structures or naval operations. Recently, there has been a major interest in wave climate changes as a result of global warming. Therefore, studies on predicting the effect of global warming on ocean wave climate are required. The objectives of this study are to analyze the accuracy and variability of global significant wave height hindcast for the 25 year period 1979-2003. This study describes the 25 year global significant wave height simulation derived from the Japan Meteorology Agency/Meteorology Research Institute (JMA/MRI)-AGCM3.2 wind climate data. The wind climate data were input into ocean wave model WAM with a global grid of spacing 1o in latitude by 1o in longitude. In situ wind and wave data sets from National Data Buoy Center (NDBC)-National Oceanic and Atmospheric Administration (NOAA) database were used to evaluate the hindcast accuracy. The validation showed good agreement both wind and waves data. The wave hindcast analysis show that the seasonal variability of significant wave height in the Northern Hemisphere is greater than in the Southern Hemisphere. Meanwhile, most of the equatorial regions are in calm condition all year.

Wave Power Statistics for Sea States

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Dag Myrhaug ◽  
Bernt J. Leira ◽  
Håvard Holm
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Bivariate Distribution ◽  
Wave Power ◽  
Power Devices ◽  
Characteristic Wave ◽  
Significant Wave ◽  
Wave Power Potential

This paper provides a bivariate distribution of wave power and significant wave height, as well as a bivariate distribution of wave power and a characteristic wave period for sea states, and the statistical aspects of wave power for sea states are discussed. This is relevant for, e.g., making assessments of wave power devices and their potential for converting energy from waves. The results can be applied to compare systematically the wave power potential at different locations based on long term statistical description of the wave climate.

scholarly journals Wave Analysis for Offshore Aquaculture Projects: A Case Study for the Eastern Mediterranean Sea

Climate ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 2
Author(s):  
Flora E. Karathanasi ◽  
Takvor H. Soukissian ◽  
Daniel R. Hayes
Keyword(s):  
Mediterranean Sea ◽  
Wave Height ◽  
Significant Wave Height ◽  
Eastern Mediterranean ◽  
Wave Climate ◽  
Eastern Mediterranean Sea ◽  
Significant Wave ◽  
Offshore Aquaculture

The investigation of wave climate is of primary concern for the successful implementation of offshore aquaculture systems as waves can cause significant loads on them. Up until now, site selection and design (or selection) of offshore cage system structures on extended sea areas do not seem to follow any specific guidelines. This paper presents a novel methodology for the identification of favorable sites for offshore aquaculture development in an extended sea area based on two important technical factors: (i) the detailed characterization of the wave climate, and (ii) the water depth. Long-term statistics of the significant wave height, peak wave period, and wave steepness are estimated on an annual and monthly temporal scale, along with variability measures. Extreme value analysis is applied to estimate the design values and associated return periods of the significant wave height; structures should be designed based on this data, to avoid partial or total failure. The Eastern Mediterranean Sea is selected as a case study, and long-term time series of wave spectral parameters from the ERA5 dataset are utilized. Based on the obtained results, the most favorable areas for offshore aquaculture installations have been identified.

Measuring Global Ocean Wave Skewness by Retracking RA-2 Envisat Waveforms

2007 ◽  
Vol 24 (6) ◽  
pp. 1102-1116 ◽  
Author(s):  
J. Gómez-Enri ◽  
C. P. Gommenginger ◽  
M. A. Srokosz ◽  
P. G. Challenor ◽  
J. Benveniste
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Likelihood Estimation ◽  
Ocean Waves ◽  
Ocean Wave ◽  
Global Ocean ◽  
Radar Altimeter ◽  
Significant Wave ◽  
Linear And Nonlinear ◽  
The Impact

For early satellite altimeters, the retrieval of geophysical information (e.g., range, significant wave height) from altimeter ocean waveforms was performed on board the satellite, but this was restricted by computational constraints that limited how much processing could be performed. Today, ground-based retracking of averaged waveforms transmitted to the earth is less restrictive, especially with respect to assumptions about the statistics of ocean waves. In this paper, a theoretical maximum likelihood estimation (MLE) ocean waveform retracker is applied tothe Envisat Radar Altimeter system (RA-2) 18-Hz averaged waveforms under both linear (Gaussian) and nonlinear ocean wave statistics assumptions, to determine whether ocean wave skewness can be sensibly retrieved from Envisat RA-2 waveforms. Results from the MLE retracker used in nonlinear mode provide the first estimates of global ocean wave skewness based on RA-2 Envisat averaged waveforms. These results show for the first time geographically coherent skewness fields and confirm the notion that large values of skewness occur primarily in regions of large significant wave height. Results from the MLE retracker run in linear and nonlinear modes are compared with each other and with the RA-2 Level 2 Sensor Geophysical Data Records (SGDR) products to evaluate the impact of retrieving skewness on other geophysical parameters. Good agreement is obtained between the linear and nonlinear MLE results for both significant wave height and epoch (range), except in areas of high-wave-height conditions.

scholarly journals Wave climatology in the Arkona Basin, the Baltic Sea

2011 ◽  
Vol 8 (6) ◽  
pp. 2237-2270 ◽  
Author(s):  
T. Soomere ◽  
R. Weisse ◽  
A. Behrens
Keyword(s):  
Baltic Sea ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Extreme Wave ◽  
The Baltic Sea ◽  
Significant Wave ◽  
Wave Heights ◽  
The Baltic

Abstract. The basic features of the wave climate in the South-Eastern Baltic Sea are studied based on available long-term measurements and simulations. The analysis of average, typical and extreme wave conditions, frequency of occurrence of different wave parameters, variations in wave heights from weekly to decadal scales, etc., is performed based on waverider measurements at the Darss Sill since 1991. The measured climatology is compared against numerical simulations with the WAM wave model driven by downscaled reanalysis of wind fields for 1958–2002 and by adjusted geostrophic winds for 1970–2007. The wave climate in this region is typical for semi-enclosed basins of the Baltic Sea. The maximum wave heights are about half of those in the Baltic Proper. The overall reliably recorded maximum significant wave height HS =4.46 m occurred during a severe S-SW storm in 1993 when the 10-min average wind speed reached 28 m s−1. The long-term average significant wave height (0.75 m) shows modest interannual (about 12 % of the long-term mean) and substantial seasonal variation. The wave periods are mostly concentrated in a narrow range of 2.5–4 s and their distribution is almost constant over decades. The role of remote swell is very small. The annual wave properties show large interannual variability but no long-term trends in average and extreme wave heights can be observed.

scholarly journals STATISTICAL MODELLING OF LONG-TERM WAVE CLIMATES

1986 ◽  
Vol 1 (20) ◽  
pp. 4 ◽  
Author(s):  
Richard Burrows ◽  
Barham A. Salih
Keyword(s):  
Data Base ◽  
Wave Height ◽  
Significant Wave Height ◽  
Joint Probability ◽  
Statistical Modelling ◽  
Wave Climate ◽  
Statistical Properties ◽  
Significant Wave ◽  
Wave Data

The paper discusses the long-term statistical properties of ocean and coastal wave climates derived from the analysis of instrumental wave data. The aim of the work reported has been to determine the theoretical distributions, from those commonly used in analysis of wave data, which best describe the joint probability of significant wave height, Hs, and mean zero-upcrossing period, Tz. A method of modelling the wave climate in this manner has been developed utilizing parametric means of specification. The data base used in the study covers records from 18 sites around the British Isles.

Wave Power Statistics for Sea States

2009 ◽  
Author(s):  
Dag Myrhaug ◽  
Bernt J. Leira ◽  
Ha˚vard Holm
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Bivariate Distribution ◽  
Wave Power ◽  
Power Devices ◽  
Significant Wave ◽  
Wave Power Potential

The paper provides a bivariate distribution of wave power and significant wave height, and the statistical aspects of wave power for sea states are discussed. This is relevant for e.g. making assessments of wave power devices and their potential for converting energy from waves. The results can be applied to compare systematically the wave power potential at different locations based on long term statistical description of the wave climate.

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