A Bayesian hierarchical spatio-temporal model for significant wave height in the North Atlantic

2011 ◽  
Vol 26 (5) ◽  
pp. 609-632 ◽  
Author(s):  
Erik Vanem ◽  
Arne Bang Huseby ◽  
Bent Natvig
Keyword(s):  
Wave Height ◽  
North Atlantic ◽  
Significant Wave Height ◽  
Bayesian Hierarchical ◽  
Significant Wave ◽  
The North ◽  
Temporal Model ◽  
The North Atlantic ◽  
Spatio Temporal

scholarly journals Variability of the Winter Wind Waves and Swell in the North Atlantic and North Pacific as Revealed by the Voluntary Observing Ship Data

2006 ◽  
Vol 19 (21) ◽  
pp. 5667-5685 ◽  
Author(s):  
Sergey K. Gulev ◽  
Vika Grigorieva
Keyword(s):  
Interannual Variability ◽  
Wave Height ◽  
North Atlantic ◽  
North Pacific ◽  
Significant Wave Height ◽  
Wind Wave ◽  
Significant Wave ◽  
The North ◽  
The North Atlantic ◽  
Wind Sea

Abstract This paper analyses secular changes and interannual variability in the wind wave, swell, and significant wave height (SWH) characteristics over the North Atlantic and North Pacific on the basis of wind wave climatology derived from the visual wave observations of voluntary observing ship (VOS) officers. These data are available from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS) collection of surface meteorological observations for 1958–2002, but require much more complicated preprocessing than standard meteorological variables such as sea level pressure, temperature, and wind. Visual VOS data allow for separate analysis of changes in wind sea and swell, as well as in significant wave height, which has been derived from wind sea and swell estimates. In both North Atlantic and North Pacific midlatitudes winter significant wave height shows a secular increase from 10 to 40 cm decade−1 during the last 45 yr. However, in the North Atlantic the patterns of trend changes for wind sea and swell are quite different from each other, showing opposite signs of changes in the northeast Atlantic. Trend patterns of wind sea, swell, and SWH in the North Pacific are more consistent with each other. Qualitatively the same conclusions hold for the analysis of interannual variability whose leading modes demonstrate noticeable differences for wind sea and swell. Statistical analysis shows that variability in wind sea is closely associated with the local wind speed, while swell changes can be driven by the variations in the cyclone counts, implying the importance of forcing frequency for the resulting changes in significant wave height. This mechanism of differences in variability patterns of wind sea and swell is likely more realistic than the northeastward propagation of swells from the regions from which the wind sea signal originates.

scholarly journals Assessment of the Storm Avoidance Effect on the Wave Climate along the Main North Atlantic Routes

2015 ◽  
Vol 69 (1) ◽  
pp. 127-144 ◽  
Author(s):  
Roberto Vettor ◽  
C. Guedes Soares
Keyword(s):  
Wave Height ◽  
North Atlantic ◽  
Significant Wave Height ◽  
Numerical Models ◽  
Wave Climate ◽  
Scatter Diagram ◽  
Significant Wave ◽  
The North ◽  
The Mean ◽  
The North Atlantic

The wave climate along the main transoceanic routes of the North Atlantic sub basin is determined using three different databases: two derived by numerical models in the HIPOCAS and ERA40 databases and one from Voluntary Observing Ships. For each route the distribution of the mean significant wave height along the path is computed as well as the specific scatter diagram. In addition an assessment of the relative wave heading probability is provided. The results highlight a bias in the visual observations especially in the summer and, more in general, for low sea states. The correction of this bias allows better understanding of rough weather avoidance by ships and to determine a storm avoidance correction.

Evolution of the Extreme Wave Region in the North Atlantic Using a 23 Year Hindcast

2015 ◽  
Author(s):  
Sonia Ponce de León ◽  
João H. Bettencourt ◽  
Joseph Brennan ◽  
Frederic Dias
Keyword(s):  
Wave Height ◽  
North Atlantic ◽  
Significant Wave Height ◽  
Extreme Values ◽  
Extreme Wave ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Significant Wave ◽  
The North ◽  
The North Atlantic

The IOWAGA data base for the North Atlantic region was used to identify the region where extreme values of significant wave height are more likely to occur. The IOWAGA database [1] was obtained from the WAVEWATCH III model [2] hindcast using the CFSR (Climate Forecast System Reanalysis) from NOAA [3,4]. The period of the study covers 1990 up to 2012 (23 years). The variability of the significant wave height was assessed by computing return periods for sea storms where the significant wave height exceeds a given threshold. The return periods of sea storms where the Hs exceeds extreme values for the north Atlantic region were computed allowing for the identification of the extreme wave regions which show that extreme waves are more likely to occur in the storm track regions of the tropical and extratropical north Atlantic cyclones.

A Bayesian-Hierarchical Space-Time Model for Significant Wave Height Data

2011 ◽  
Author(s):  
Erik Vanem ◽  
Arne Bang Huseby ◽  
Bent Natvig
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
North Atlantic Ocean ◽  
Space Time ◽  
Maritime Transportation ◽  
Time Model ◽  
Bayesian Hierarchical ◽  
Significant Wave ◽  
The North ◽  
Future Return

Bad weather and rough seas contribute significantly to the risk to maritime transportation. This stresses the importance of taking severe sea state conditions adequately into account, with due treatment of the uncertainties involved, in ship design and operation. Hence, there is a need for appropriate stochastic models describing the variability of sea states. This paper presents a Bayesian hierarchical space-time stochastic model for significant wave height. The model has been fitted by data for an area in the North Atlantic ocean and aims at describing the temporal and spatial variability of significant wave height in this area. It could also serve as foundation for further extensions used for long-term prediction of significant wave height and future return periods of extreme significant wave heights. The model will be outlined in this paper, and the results will be discussed. Furthermore, a discussion of possible model extensions will be presented.

Composite distribution of North Atlantic extreme wind waves inferred from satellite altimetry data

2020 ◽  
Author(s):  
Sonia Ponce de León ◽  
Joao Bettencourt
Keyword(s):  
Wave Height ◽  
North Atlantic ◽  
Significant Wave Height ◽  
Satellite Altimetry ◽  
Extratropical Cyclones ◽  
Altimetry Data ◽  
The North ◽  
The North Atlantic ◽  
Low Pressure Systems ◽  
Satellite Altimetry Data

<p>The north Atlantic Ocean is regularly traversed by extratropical cyclones and winter low pressure systems originated in the Western part of the basin that can potentially generate dangerous extreme sea states. The region where these extreme sea states occur is linked to the tracks of the low-pressure systems in the north Atlantic basin.</p><p>Extreme sea states are usually generated by storms that can traverse whole ocean basins and generate high-energy swells that can propagate for thousands of kilometers. Additionally, rogue waves are a recognized source of extreme waves that needs to be considered when designing for operation at sea.</p><p>This study aims at the spatial distribution of the mean and extreme wave significant wave height inside the extratropical cyclones. We studied the significant wave height distribution of extratropical cyclones using merged satellite altimetry data to produce composite maps of this sea state variable. Although there are large variations among individual cyclones, the compositing method allows obtaining general features. We find that the higher waves are in the south-eastern quadrant of the cyclone, due to the extended fetch mechanism. The highest wave heights are found during the 48h period when the cyclone’s strength is maximum.</p><p> </p>

scholarly journals Bayesian hierarchical modelling of North Atlantic windiness

2013 ◽  
Vol 13 (3) ◽  
pp. 545-557 ◽  
Author(s):  
E. Vanem ◽  
O. N. Breivik
Keyword(s):  
Climate Change ◽  
Wave Height ◽  
North Atlantic ◽  
Environmental Conditions ◽  
Significant Wave Height ◽  
Weather Conditions ◽  
Extreme Weather ◽  
Bayesian Hierarchical ◽  
Significant Wave

Abstract. Extreme weather conditions represent serious natural hazards to ship operations and may be the direct cause or contributing factor to maritime accidents. Such severe environmental conditions can be taken into account in ship design and operational windows can be defined that limits hazardous operations to less extreme conditions. Nevertheless, possible changes in the statistics of extreme weather conditions, possibly due to anthropogenic climate change, represent an additional hazard to ship operations that is less straightforward to account for in a consistent way. Obviously, there are large uncertainties as to how future climate change will affect the extreme weather conditions at sea and there is a need for stochastic models that can describe the variability in both space and time at various scales of the environmental conditions. Previously, Bayesian hierarchical space-time models have been developed to describe the variability and complex dependence structures of significant wave height in space and time. These models were found to perform reasonably well and provided some interesting results, in particular, pertaining to long-term trends in the wave climate. In this paper, a similar framework is applied to oceanic windiness and the spatial and temporal variability of the 10-m wind speed over an area in the North Atlantic ocean is investigated. When the results from the model for North Atlantic windiness is compared to the results for significant wave height over the same area, it is interesting to observe that whereas an increasing trend in significant wave height was identified, no statistically significant long-term trend was estimated in windiness. This may indicate that the increase in significant wave height is not due to an increase in locally generated wind waves, but rather to increased swell. This observation is also consistent with studies that have suggested a poleward shift of the main storm tracks.

Comparison of Bivariate Models of the Distribution of Significant Wave Height and Peak Wave Period

2007 ◽  
Author(s):  
Catarina S. Soares ◽  
C. Guedes Soares
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Bivariate Normal Distribution ◽  
Wave Period ◽  
Peak Period ◽  
Data Set ◽  
Significant Wave ◽  
The North ◽  
Bivariate Models ◽  
The North Sea

This paper presents the results of a comparison of the fit of three bivariate models to a set of 14 years of significant wave height and peak wave period data from the North Sea. One of the methods defines the joint distribution from a marginal distribution of significant wave height and a set of distributions of peak period conditional on significant wave height. Other method applies the Plackett model to the data and the third one applies the Box-Cox transformation to the data in order to make it approximately normal and then fits a bivariate normal distribution to the transformed data set. It is shown that all methods provide a good fit but each one have its own strengths and weaknesses, being the choice dependent on the data available and applications in mind.

Comparison Between a Fatigue Model for Voyage Planning and Measurements of a Container Vessel

2009 ◽  
Author(s):  
Wengang Mao ◽  
Jonas W. Ringsberg ◽  
Igor Rychlik ◽  
Gaute Storhaug
Keyword(s):  
Fatigue Damage ◽  
Wave Height ◽  
Significant Wave Height ◽  
Route Planning ◽  
Estimation Model ◽  
Ongoing Research ◽  
Significant Wave ◽  
The North ◽  
Fatigue Damage Accumulation ◽  
Fatigue Model

This paper presents results from an ongoing research project which aims at developing a numerical tool for route planning of container ships. The objective with the tool is to be able to schedule a route that causes minimum fatigue damage to a vessel before it leaves port. Therefore a new simple fatigue estimation model, only using encountered significant wave height, is proposed for predicting fatigue accumulation of a vessel during a voyage. The formulation of the model is developed based on narrow-band approximation. The significant response height hs, is shown to have a linear relationship with its encountered significant wave height Hs. The zero up-crossing response frequency fz, is represented as the corresponding encountered wave frequency and is expressed as a function of Hs. The capacity and accuracy of the model is illustrated by application on one container vessel’s fatigue damage accumulation, for different voyages, operating in the North Atlantic during 2008. For this vessel, all the necessary data needed in the fatigue model, and for verification of it, was obtained by measurements. The results from the proposed fatigue model are compared with the well-known and accurate rain-flow estimation. The conclusion is that the estimations made using the current fatigue model agree well with the rain-flow method for almost all of the voyages.

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