Ocean Swell: How Much Do We Know

2017 ◽  
Author(s):  
Alexander V. Babanin ◽  
Haoyu Jiang
Keyword(s):  
Wave Amplitude ◽  
Arrival Time ◽  
Frequency Dispersion ◽  
Nonlinear Effects ◽  
Joint Analysis ◽  
Wave Forecast ◽  
Model Predictions ◽  
Forecast Models ◽  
Maritime Operations ◽  
Definition Of

Swell waves are present in more than 80% of ocean seas, and provide significant adverse impact on maritime operations. Their prediction by wave-forecast models, however, is poor, both in terms of wave amplitude and, particularly, arrival time. The very definition of ocean swell is ambiguous: while it is usually perceived as former wind-generated waves, in fact it may reconnect with the local wind through nonlinear interactions. The paper will bring together an overview of the complex swell problem. The visible swell attenuation is driven by a number of dissipative and non-dissipative processes. The dissipative phenomena include interaction with turbulence on the water and air sides, with adverse winds or currents. Non-dissipative contributions to the gradual decline of wave amplitude come from frequency dispersion, directional spreading, refraction by currents, and lateral diffraction of wave energy. The interactions with local winds/waves can, on the contrary, cause swell growth. Swell arrival time is the least understood and the most uncertain problem. Joint analysis of buoy observations and model reanalysis shows that swell can be tens of hours early or late by comparison with model predictions. Linear and nonlinear effects which can contribute to such biases are discussed.

scholarly journals TSUNAMI PHASE SPEED REDUCTION DUE TO WATER COMPRESSIBILTY

2018 ◽  
pp. 9
Author(s):  
Ali Abdolali ◽  
James T. Kirby
Keyword(s):  
Arrival Time ◽  
Phase Speed ◽  
Propagation Speed ◽  
Frequency Dispersion ◽  
Wave Theory ◽  
Polar Coordinates ◽  
Ocean Bottom ◽  
Tsunami Propagation ◽  
Boussinesq Model ◽  
Tsunami Waves

Most existing tsunami propagation models consider the ocean to be an incompressible, homogenous medium. Recently, it has been shown that a number of physical features can slow the propagation speed of tsunami waves, including wave frequency dispersion, ocean bottom elasticity, water compressibility and thermal or salinity stratification. These physical effects are secondary to the leading order, shallow water or long wave behavior, but still play a quantifiable role in tsunami arrival time, especially at far distant locations. In this work, we have performed analytical and numerical investigations and have shown that consideration of those effects can actually improve the prediction of arrival time at distant stations, compared to incompressible forms of wave equations. We derive a modified Mild Slope Equation for Weakly Compressible fluid following the method proposed by Sammarco et al. (2013) and Abdolali et al. (2015) using linearized wave theory, and then describe comparable extensions to the Boussinesq model of Kirby et al. (2013). Both models account for water compressibility and compression of static water column to simulate tsunami waves. The mild slope model is formulated in plane Cartesian coordinates and is thus limited to medium propagation distances, while the Boussinesq model is formulated in spherical polar coordinates and is suitable for ocean scale simulations.

scholarly journals TSUNAMI GENERATION AND PROPAGATION

1972 ◽  
Vol 1 (13) ◽  
pp. 146
Author(s):  
Joseph L. Hammack ◽  
Frederic Raichlen
Keyword(s):  
Linear Theory ◽  
Source Region ◽  
Three Dimensional ◽  
Frequency Dispersion ◽  
Nonlinear Effects ◽  
Its Region ◽  
Experimental Results ◽  
Specific Class ◽  
Two Dimensional ◽  
Three Dimensional Models

A linear theory is presented for waves generated by an arbitrary bed deformation {in space and time) for a two-dimensional and a three -dimensional fluid domain of uniform depth. The resulting wave profile near the source is computed for both the two and three-dimensional models for a specific class of bed deformations; experimental results are presented for the two-dimensional model. The growth of nonlinear effects during wave propagation in an ocean of uniform depth and the corresponding limitations of the linear theory are investigated. A strategy is presented for determining wave behavior at large distances from the source where linear and nonlinear effects are of equal magnitude. The strategy is based on a matching technique which employs the linear theory in its region of applicability and an equation similar to that of Korteweg and deVries (KdV) in the region where nonlinearities are equal in magnitude to frequency dispersion. Comparison of the theoretical computations with the experimental results indicates that an equation of the KdV type is the proper model of wave behavior at large distances from the source region.

On Non-Propositional Aspects in Modelling Complex Systems

2010 ◽  
Vol 32 (1) ◽  
Author(s):  
Rafaela Hillerbrand
Keyword(s):  
Complex System ◽  
Complex Systems ◽  
Climate Modeling ◽  
Climate System ◽  
Practical Significance ◽  
Political Decision ◽  
Model Predictions ◽  
Epistemic Notion ◽  
Definition Of ◽  
Political Decision Making

AbstractThis paper aims to show that modeling complex systems inevitably involves non-propositional knowledge and thus the uncertainties associated with the corresponding model predictions cannot be fully quantified. This is exemplified by means of the climate system and climate modeling. The climate system is considered as a paradigm for a complex system, whereby the notion of complexity adopted in this paper is epistemic in nature and does not equate with the technical definition of a complex system as for example used within physics or complexity theory. The epistemic notion of complexity allows to view the climate system as complex with respect to some features, while simple with respect to others. This distinction is of practical significance for political decision making as it allows to treat some climate predictions as (fairly) certain, while acknowledging high uncertainties with others.

Nonlinear Effects in Resonantly Driven Surface Waves on Fluids

1972 ◽  
Vol 50 (19) ◽  
pp. 2235-2243
Author(s):  
F. L. Curzon ◽  
G. N. Ionides
Keyword(s):  
Surface Waves ◽  
Electric Fields ◽  
Driving Force ◽  
Wave Amplitude ◽  
Nonlinear Effects ◽  
Microwave Resonator ◽  
Electrode Geometry ◽  
Fluid Surface ◽  
Electric Stress ◽  
Time Periodic

The results presented in this paper show that fluid surface waves, resonantly driven by spatially nonuniform, time periodic electric fields, exhibit nonlinear effects when the wave amplitude ξ exceeds a significant fraction of the distance D between the driver electrode and the fluid surface. The phase difference between the surface wave and the driving force, as well as the dependence of wave amplitude on the electric stress are computed and compared with experimental results. For ξ/D exceeding ~0.7 (dependent on electrode geometry) the surface waves excited are unstable (also confirmed experimentally). The experiments are performed on surface waves on mercury contained in a cylindrical microwave resonator. Shifts in the microwave resonant frequency (caused by the surface waves) monitor the displacement of the fluid surface.

scholarly journals A note on tsunamis: their generation and propagation in an ocean of uniform depth

1973 ◽  
Vol 60 (4) ◽  
pp. 769-799 ◽  
Author(s):  
Joseph L. Hammack
Keyword(s):  
Linear Theory ◽  
Linear Approximation ◽  
Frequency Dispersion ◽  
Nonlinear Effects ◽  
Solid Boundary ◽  
Far Field ◽  
Bed Deformation ◽  
Downstream Region ◽  
Generation Region ◽  
Block Section

The waves generated in a two-dimensional fluid domain of infinite lateral extent and uniform depth by a deformation of the bounding solid boundary are investigated both theoretically and experimentally. An integral solution is developed for an arbitrary bed displacement (in space and time) on the basis of a linear approximation of the complete (nonlinear) description of wave motion. Experimental and theoretical results are presented for two specific deformations of the bed; the spatial variation of each bed displacement consists of a block section of the bed moving vertically either up or down while the time-displacement history of the block section is varied. The presentation of results is divided into two sections based on two regions of the fluid domain: a generation region in which the bed deformation occurs and a downstream region where the bed position remains stationary for all time. The applicability of the linear approximation in the generation region is investigated both theoretically and experimentally; results are presented which enable certain gross features of the primary wave leaving this region to be determined when the magnitudes of parameters which characterize the bed displacement are known. The results indicate that the primary restriction on the applicability of the linear theory during the bed deformation is that the total amplitude of the bed displacement must remain small compared with the uniform water depth; even this restriction can be relaxed for one type of bed motion.Wave behaviour in the downstream region of the fluid domain is discussed with emphasis on the gradual growth of nonlinear effects relative to frequency dispersion duringpropagationand the subsequent breakdown of the linear theory. A method is presented for finding the wave behaviour in the far field of the downstream region, where the effects of nonlinearities and frequency dispersion have become about equal. This method is based on the use of a model equation in the far field (which includes both linear and nonlinear effects in an approximate manner) first used by Peregrine (1966) and morerecently advocated by Ben jamin, Bona & Mahony (1972) as a preferable model to the more commonly used equation of Korteweg & de Vries (1895). An input-output approach is illustrated for the numerical solution of this equation where the input is computed from the linear theory in its region of applicability. Computations are presented and compared with experiment for the case of a positive bed displacement where the net volume of the generated wave is finite and positive; the results demonstrate the evolution of a train of solitary waves (solitons) ordered by amplitude followed by a dispersive train of oscillatory waves. The case of a negative bed displacement in which the net wave volume is finite and negative (and the initial wave is negative almost everywhere) is also investigated; the results suggest that only a dispersive train of waves evolves (no solitons) for this case.

Safe and Fuel-Efficient Voyage Planning for the Northeast Passage by Combining Reliable Ship Performance, Weather and Ice Forecast Models

2020 ◽  
Author(s):  
Zhiyuan Li ◽  
Jonas W. Ringsberg ◽  
Li Ding ◽  
Fransisco Rita ◽  
Nicolas Fournier ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Risk Mitigation ◽  
Forecast Model ◽  
Energy System ◽  
The Arctic ◽  
Operational Conditions ◽  
Energy System Model ◽  
Forecast Models ◽  
Maritime Operations ◽  
Ship Performance

Abstract The Northeast Passage in the Arctic between Europe and Asia offers a significantly shorter voyage compared to the Southern route through the Suez Canal. In 2017, the EU research project “Safe maritime operations under extreme conditions: the Arctic case (SEDNA)” was established to perform a comprehensive analysis of Arctic transit shipping and to promote technical solutions for this purpose. This paper is based on the deliverables of the SEDNA project. A voyage planning tool (VPT) for Arctic applications was developed to plan the optimal route regarding ship’s fuel consumption and safety. One of the most advanced metocean and ice forecast model is utilized to provide comprehensive environmental conditions that are synchronized and will be updated frequently during the voyage. The ship energy system model takes into account the various environmental variables as well as ship’s operational conditions to compute the ship performance in both open and ice infested waters. For Arctic operations, specific ice resistance models are implemented in the VPT, and a user has the options of either relying on icebreaker assistance or going for unassisted navigation in part of the entire Arctic passage. Case study voyages of different ship types, route options, staring time, home/destination ports are simulated to demonstrate how various optimal routes are planned and how the transit time and fuel consumption vary. This information is considered being crucial for ship owners for planning their voyages in advance. The continuously updated voyage information from the VPT is particularly helpful for the ship crew if there are specific ship operations and risk mitigation actions that need to be taken care of during the voyage. In addition, this study underlines that a safe and fuel-efficient Arctic passage requires viable voyage planning tools that combine reliable ship performance with weather and ice forecasts.

Integration of Hydro and Renewable Energy Resources in Energy Planning

2020 ◽  
Author(s):  
Lucero Cynthia Luciano De La Cruz ◽  
Cesar Celis
Keyword(s):  
Renewable Energy ◽  
Energy Transition ◽  
Forecast Model ◽  
Energy Resources ◽  
Energy Planning ◽  
Renewable Energy Resources ◽  
Short Term ◽  
Hydropower Plants ◽  
Forecast Models ◽  
Definition Of

Abstract Renewable energy is the energy obtained from resources inexhaustible in the long term. Furthermore, in some countries, non-conventional renewable energy includes solar, wind, biomass, geothermal and mini-hydropower. The definition of mini-hydropower plants varies depending on the country. As an example, in Peru and Canada, mini-hydropower plants have different installing capacities, below 20MW and 50MW, respectively. Accordingly, this work (i) discusses the Energy Balance and challenges that renewable energies have to face on their way to the energy transition, (ii) highlights the forecast models to generate renewable energy in short-term energy planning. The historical data about the renewable energy resources and the energy produced have been obtained by COES. The R studio software was used for statistical analysis of renewable resources and electricity generation. Also, a forecast model was developed using a neural network to forecast renewable energy generation. The results show a strong correlation between hydro resources and non-conventional renewable energy resources. Finally, the data obtained from the renewable generation forecast model were used as input to carry out a short-term dispatch model using GAMS software to determine the forecast of daily marginal cost in SEIN.

scholarly journals Generation of Plasma Flows and Filamentation of Magnetic Fields in the Solar Atmosphere

1993 ◽  
Vol 141 ◽  
pp. 549-553
Author(s):  
Margarita Ryutova
Keyword(s):  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Acoustic Streaming ◽  
Nonlinear Effects ◽  
General Definition ◽  
Solar Magnetic Fields ◽  
Plasma Flows ◽  
Magnetic Structures ◽  
Definition Of

AbstractNonlinear effects in dynamics of solar magnetic fields which, in particular, determine the evolution of solar magnetic structures and their lifetimes, are discussed. By some analogy with the effects of acoustic streaming in usual hydrodynamics the general definition of these effects as “magneto acoustic streaming” is proposed.

Characteristics of Leading Tsunami Waves Generated in Three Recent Tsunami Events

2014 ◽  
Vol 08 (03) ◽  
pp. 1440001 ◽  
Author(s):  
Chao An ◽  
Philip L.-F. Liu
Keyword(s):  
Water Depth ◽  
Wave Amplitude ◽  
Propagation Speed ◽  
Frequency Dispersion ◽  
Wave Period ◽  
Wave Crest ◽  
Haida Gwaii ◽  
Tsunami Waves ◽  
Wave Nonlinearity ◽  
Chile Tsunami

In this paper, the time series of ocean water surface elevation, recorded by Deep-ocean Assessment and Recording of Tsunamis (DART) sensors in the Pacific Ocean, during three recent tsunami events — 2010 Chile tsunami, 2011 Tohoku tsunami, and 2012 Haida Gwaii tsunami — are analyzed. The characteristics of leading tsunami waves are examined in terms of their propagation speed, wave period and wave amplitude so as to determine the importance of wave nonlinearity and frequency dispersion. Using the estimated arrival time of leading waves at each DART station and the distance from each station to the epicenter of the corresponding earthquake, the averaged propagation speed of leading waves for each event is calculated. It is found that the wave propagation speed for 2010 Chile tsunami is roughly 190 m/s, and is slightly slower than that of 2011 Tohoku and 2012 Haida Gwaii tsunamis, 210 m/s for both events. Two time scales associated with the leading waves are introduced: the duration of leading wave crest and the leading wave period obtained from a wavelet analysis. The results show that the leading wave crest duration is roughly 15–20 min and the wave period is roughly 25–30 min at most of DART stations for all the three events. The wave nonlinearity and frequency dispersion parameters, being defined as the wave amplitude to water depth ratio and the square of water depth to wavelength ratio, respectively, are calculated for the leading waves. The parameter for wave nonlinearity is found to be smaller than 4.0 × 10-4, while the parameter for frequency dispersion is smaller than 0.02 at all stations for all the three events. Finally, the cumulative effects of nonlinearity and frequency dispersion for the leading waves are investigated. It is found that the distances between the epicenter and all DART stations in each event are much smaller than those required for the nonlinearity and/or frequency dispersive effects to become significant.

Geodetic deformation rates and driving processes in metropolitan France and neighboring Western Europe

2020 ◽  
Author(s):  
Stephane Mazzotti ◽  
Juliette Grosset ◽  
Christine Masson ◽  
Philippe Vernant
Keyword(s):  
Plate Tectonics ◽  
Western Europe ◽  
Western Alps ◽  
Joint Analysis ◽  
Normal Extension ◽  
Isostatic Adjustment ◽  
Definition Of ◽  
A Minor ◽  
Aquitaine Basin ◽  
Rhone Valley

<p>We constrain present-day deformation rates and styles in metropolitan France and neighboring Western Europe using a dataset of ca. 1200 GNSS horizontal and vertical velocities from continuous and semi-continuous stations. The characterization and correction of network-scale common-mode noise, combined with two independent network analysis technics allow the resolution of very small horizontal velocities (resp. strain rates) with a 95% confidence ca. 0.1–0.2 mm/yr (resp. ca. 1 x 10<sup>-9</sup> yr<sup>-9</sup>) on a spatial scale of 100–200 km. The resulting velocity and strain rate fields show regional coherent patterns that can be associated with features that have been previously identified (e.g., orogen-normal extension in the Pyrenees and Western Alps), but also with new deformation patterns such as North-South shortening in northeastern France - southwestern Germany north of the Alpine Front (Vosges - Rhine Graben - Black Forest). A joint analysis of these new geodetic data with seismicity and focal mechanism catalogs allows the definition of regional seismo-tectonic models that can be compared with the numerous models of deformation processes proposed for Western Europe, from plate tectonics to erosion or Glacial Isostatic Adjustment. We show that plate and micro-plate tectonics play a minor (probably negligible) role in present-day deformation in metropolitan France and that alternative non-tectonic processes must be considered to better understand the origin of recent moderate earthquakes such as the March 2019 Ml=4.9 Montendre earthquake in the Aquitaine Basin or the Nov. 2019 Mw=4.8 Teil earthquake in the Rhone Valley.</p>

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