Variational Wave Research Articles

Spatial Variability of Surface Waves and Nearshore Currents Induced by Hurricane Harvey along the Southern Texas Coast

Extreme weather events such as hurricanes are expected to become more severe with the human-induced increase in average global temperatures, exacerbating the risk of major damage. Efforts to predict these events typically require detailed hydrodynamic data that are difficult to collect in the field. Here, nearshore data collected with three ADCP moorings were used to describe the hydrodynamics induced by Hurricane Harvey along the southern Texas coast. Wave spectra and nearshore current variations were analyzed along the hurricane’s trajectory and compared to other offshore locations. The results indicate that winds intensified along the coast as Harvey approached the Port Aransas coastline. Southerly wind stresses of ~−0.9 Nm−2 generated ~2 ms−1 depth-averaged flows towards the southwest close to landfall in the north, while flows of ~1 ms−1 and <1 ms−1 were measured in the center and the south of the study site, respectively. The hydrodynamics induced by the hurricane were compared to those induced by an intense synoptic-scale cold front (CF). Both events generated southward-directed alongshore wind stresses of similar magnitudes (τy ~−0.4 Nm−2) that caused similar depth-averaged flows (0.5 to 0.7 ms−1) and wave energy conditions (Hs of ~4 m) in the south. Harvey caused extremely energetic conditions close to landfall in the north compared to the CF; depth-averaged flows and Hs of 2 ms−1 and 10 m were induced by Harvey, as opposed to 0.6 ms−1 and 4 m by the CF, respectively. While intense currents (>1 ms−1) and waves (Hs > 4 m) lasted for less than a day during Harvey, these persisted a few days longer during the CF. This study highlights the relevant role of synoptic-scale cold fronts in modulating the nearshore hydrodynamics, which occur more frequently than tropical cyclones in the northwestern Gulf of Mexico.

Airborne Observations of Shoaling and Breaking Internal Waves

AbstractInternal waves (IW) are crucial contributors to the transport of sediment, heat, and nutrients in coastal areas. While IW have been extensively studied using point measurements, their spatial variability is less well understood. In this paper we present a unique set of high‐resolution infrared imagery collected from a helicopter, hovering over very energetic shoaling and breaking IW. We compute surface velocities by tracking the evolution of thermal structures at the ocean surface and find horizontal velocity gradients with magnitudes that are more than 100 times the Coriolis frequency. Under the assumption of no vertical shear we determine vertical velocities from the obtained horizontal divergence estimates and identify areas of the wave undergoing breaking. The spatial variability of the internal wave occurs on scales from a few to a few hundred meters. These results highlight the need to collect spatio‐temporal observations of the evolution of IW in coastal areas.

Short-term effect of sea defense on shoreline and wave variability in Elmina Bay, Ghana

Short-term effect of sea defense on shoreline and wave variability in Elmina Bay, Ghana

What produces and what controls the spatial-temporal structuring of the magnetospheric chorus waves that create the pulsating aurora: An unsolved problem in need of new measurements

In this Perspective article discussing solved and unsolved problems in space physics, the focus is on the unsolved problem of the spatial-temporal variability of the magnetospheric plasma waves that produce the spatial-temporal atmospheric luminosity of the pulsating aurora. In particular the outstanding issue of what causes the spatial-temporal variations of the chorus-wave intensities is highlighted: Two great unknowns are (1) how does it work and (2) what are the controlling factors. The point is made that the whistler-mode chorus waves that produce the pulsating aurora are the same chorus waves that energize the Earth’s electron radiation belt. Hence, beyond not understanding the cause of pulsating aurora there is (1) a lack of understanding of the magnetosphere-ionosphere system behavior and (2) a lack of understanding of how the electron radiation belt is energized. It is noted that the pulsating aurora is perhaps the most-obvious example of an “emergent phenomena” in the magnetosphere-ionosphere-thermosphere system, and so perhaps the clearest indication that the magnetosphere-ionosphere-thermosphere system is a truly “complex system”, not just a complicated system. Future needs for solving this unsolved problem are discussed: the most-critical need is argued to be gaining an ability to measure cold-electron structuring in the equatorial magnetosphere.

Projected climate variability of internal waves in the Andaman Sea

The Andaman Sea, in the northeast Indian Ocean, is renowned for large-amplitude internal waves. Here, we use a global climate model (CanESM5) to investigate the long-term variability of internal waves in the Andaman Sea under a range of shared socioeconomic pathway (SSP) scenarios. SSPs are future societal development pathways related to emissions and land use scenarios. We project that mean values of depth-averaged stratification will increase by approximately 6% (SSP1-2.6), 7% (SSP2-4.5), and 12% (SSP5-8.5) between 1871-1900 and 2081-2100. Simulating changes in internal tides between the present (2015-2024) and the end-century (2091-2100), we find that the increase in stratification will enhance internal tide generation by approximately 4 to 8%. We project that the propagation of internal tides into the Andaman Sea and the Bay of Bengal will increase by 8 to 18% and 4 to 19%, respectively, under different SSP scenarios. Such changes in internal tides under global warming will have implications for primary production and ecosystem health not only in the Andaman Sea but also in the Bay of Bengal.

On wave impact pressure variability

The variability of the largest wave impacts, where nominally identical waves produce significantly different pressures, is widely known. However, the mechanisms are not well understood. Here we provide a review and investigation of factors affecting the variability of wave impact pressures on steep walls, quantifying the range of parameters that have been used in the literature. We then present two investigations: (i) Setup 1 on the effect of structure slope and (ii) Setup 2 on the effects of kinematics variability on pressure variability. Firstly, wave impacts arising from about 250 focused wave groups interacting with three values of wall steepness (vertical, 10° to the vertical, and 27° to the vertical) showed that steeper walls resulted in larger impact loads, the largest of which were experienced higher up the wall. The maximum pressure data was seen to be a good fit to the Gumbel model for the vertical wall but closer to the log-Normal distribution for the 10° wall. Parameter estimates for those distributions revealed a systematic variation which could potentially be used to predict maximum impact pressures at intermediate wall angles and locations. The pressure wave arising from the impact was seen to be of highly variable speed, for the 10° wall it was estimated to be about 10 m/s at the 1:25 model scale, decreasing for the 27° wall. In the second investigation, which provided kinematics data using particle tracking velocimetry, rapidly varying velocities close to the impact location were observed, with maximum values at impact being a reasonable fit to the Weibull distribution. Findings indicate that though the water surface may appear to be calm, residual sub-surface velocities undoubtedly play some role in the variability of the subsequent wave impact pressures. • Impact pressure probability distributions deduced for different wall geometries. • Parameter estimates for the probability distributions revealed a systematic variation. • Wave kinematics probability distribution obtained from particle tracking velocimetry. • Coefficient of variation of wave kinematics higher than that of impact pressures.

Rytov variance of plane and spherical waves, and scintillation index in weak to strong underwater turbulence

As a means of distinguishing the weak and strong irradiance fluctuations of optical beam propagation in turbulence, Rytov perturbation approximation and its later extension make it possible to characterize the transition between turbulence regimes. The closed-form expression of Rytov variance is derived for both plane and spherical waves propagating in underwater turbulence. Scintillation index of plane and spherical waves are also investigated depending on the Rytov variance in weak-moderate-strong underwater turbulence regimes. Moreover, the variation of signal-to-noise ratio (SNR) for an optical wireless communication system operating in underwater turbulent medium is analyzed. Results are presented for various underwater parameters. We believe that researchers may benefit from our results to find the optimum design (e.g. aperture size) and performance (e.g. SNR, bit-error-rate) parameters for an optical wireless communication systems operating in wide range underwater turbulent medium.

Swell and wind-sea partitioning of HF radar directional spectra

ABSTRACT Partitioning is a process used to separate wind-sea and swell contributions in an ocean wave directional spectrum to simplify, and hence make more useful, the interpretation of the spectrum for users of wave data. HF radar systems can measure the wave spectrum over regions of the coastal ocean from the coast to over 100 km offshore with good spatial and temporal resolution depending on the operating frequency and bandwidth. Such systems can measure hundreds of directional spectra across the field of view of the radar, so there is very strong motivation to reduce the dimensionality of the data set for practical applications using partitioning. For similar reasons partitioning methods are increasingly being used for wave model and satellite-measured spectra. A partitioning method, which extends the method of Waters J, Wyatt LR, Wolf J, Hines A. [2013. Data assimilation of partitioned HF radar wave data into Wavewatch III. Ocean Model. 72:17–31.] for HF radar data, is described, assessed using buoy data and used to demonstrate the spatial variability of both swell and wind waves in three coastal regions. The results are very encouraging. HF radar systems could therefore provide very useful data for wave model and satellite partitioning validations in coastal waters where model and satellite measurements are most challenged by wave-current interactions, coastal topography and bathymetry.

Impact of the ENSO phenomenon on wave variability in the Pacific Ocean for wind sea and swell waves

Using wave data from 1960 to 1990 from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis ERA-40 dataset and the ERA-5 reanalysis dataset (1990–2018), this paper presents a comprehensive study on the spatial and temporal variability of wind sea wave height (Hw), swell wave height (Hsw) and mixed significant wave height (Hs) in the Pacific during the warm (El Niño) and cold (La Niña) ENSO phases. The main findings show that During DJF, the Hsw is dominated by strong winds and large waves from extratropical cyclones in the North Pacific, especially from 1960 to 1990. However, from 1990–2018 these maximum values extend into the subtropical crest of the Pacific Ocean and the southeast trade winds increase during La Niña. The annual cycle of Hw, Hsw and Hs for specific points located from the west center toward the east center along the equatorial Pacific for the analyzed decades show a strong transition in the locations of the maximum and minimum values during the year. In this sense, the eastern point is more highly influenced by the swell systems that flow from the northwest and southwest of the southern hemisphere associated with the intensification of winds during the occurrence of La Niña. It is therefore not possible to determine a single period of maximum and minimum values. During the decades of 1990–2018, the difference in swell wave height during La Niña compared to El Niño increased throughout the year compared to 1960–1990. During the 1960–1990 period, the maximum values were detected in JJA for both El Niño and La Niña in an area that extends from Perú and ends toward the eastern center of the Colombian Pacific Basin.

Short timescale variability in large-amplitude internal waves on the western Portuguese shelf

Timescales in the ocean can range from the transient turbulence to the long-term climate scales. Quantifying its changes involves establishing meaningful background states, but that can be challenging if an extensive array of wave phenomena is masking the ocean's variability. Internal Waves (IWs) are a fundamental part of these wave phenomena, which are now widely acknowledged as major contributors in ocean dynamics. In this study we use satellite imagery from Synthetic Aperture Radars (SAR) and moored temperature records to assess the variability scales and magnitudes of coastal IW systems propagating onshore off the western Portuguese shelf. The data shows significant variability in timescales of just a few days, and hence within the waves' typical propagation lifespan. A regional ocean circulation model is used together with linear theory to assess how mesoscale variability is contributing to the observed variability patterns observed in the IWs in the SAR and in situ data. According to linear theory, the IW variability is mostly owing to variable mesoscale currents, which off the Portuguese coast typically result from geostrophic flows, eddies and upwelling dynamics. IW variability owing to changes in stratification is found to amount to about half of that in background flows, but their effect can go unnoticed within the largest contributions from mesoscale currents. One extreme event is highlighted in which IWs from consecutive tidal cycles could possibly decouple from (i.e. not traceable back to) their originating tides in just a few days and hence within their typical lifespans.

Solitary waves of the generalized Radhakrishnan-Kundu-Lakshmanan equation with four powers of nonlinearity

The complex Radhakrishnan-Kundu-Lakshmanan equation having polynomial law of nonlinearity with four powers is considered. The Cauchy problem for this partial differential equation cannot be solved by the inverse scattering transform and the exact solutions of this equation is looked for taking into account the traveling wave variables. The overdetermined system of nonlinear ordinary differential equations for the real and imaginary parts of the ordinary differential equation obtained is presented. The compatibility conditions are obtained. First integral of the nonlinear differential equation is found. It is shown that there exist periodic solutions of the mathematical model. Solitary wave solutions of the complex Radhakrishnan-Kundu-Lakshmanan equation are given in the form of implicit functions using the direct and special methods.

Mindfulness-Based Student Training Improves Vascular Variability Associated With Sustained Reductions in Physiological Stress Response.

In today's fast-paced society, chronic stress has become an increasing problem, as it can lead to psycho-physiological health problems. University students are also faced with stress due to the demands of many courses and exams. The positive effects of mindfulness-based stress reduction (MBSR) on stress management and self-regulation have already been studied. We have developed a new mindfulness intervention tailored for students—the Mindfulness-Based Student Training (MBST). In this study, we present longitudinal results of the MBST evaluation. Biosignal analysis methods, including pulse wave variability (PWV), heart rate variability, and respiratory activity, were used to assess participants' state of autonomic regulation during the 12-week intervention and at follow-up. The progress of the intervention group (IGR, N = 31) up to 3 months after the end of MBST was compared with that of a control group (CON, N = 34). In addition, the long-term effect for IGR up to 1 year after intervention was examined. The analysis showed significant positive changes in PWV exclusively for IGR. This positive effect, particularly on vascular function, persists 1 year after the end of MBST. These results suggest a physiologically reduced stress level in MBST participants and a beneficial preventive health care program for University students.

Advanced Model of Spatiotemporal Mining-Induced Kinematic Excitation for Multiple-Support Bridges Based on the Regional Seismicity Characteristics

In the paper, an advanced model of spatiotemporal mining-induced kinematic excitation (SMIKE) for multiple-support bridges exposed to mining-induced seismicity is proposed. The uniqueness of this model results from the possibility of its application in any region of mining activity, as it is based on empirical regression functions characterizing such regions. In the model, the loss of coherency resulting from the scattering of waves in the heterogeneous ground, the wave-passage effect originating in different arrival times of waves to consecutive supports, and the site-response effect depending on the local soil conditions are taken into account. The loss of coherency of mining-induced seismic waves is obtained by applying a random field generator based on a spatial correlation function to produce time histories of accelerations on consecutive structure supports based on an originally recorded shock. The deterministic approach is used to account for temporal wave variability. The proposed SMIKE model is applied to assess the dynamic performance of a five-span bridge under a mining-induced shock recorded in the Upper Silesian Coal Basin (USCB), Poland. The first model’s parameter (space scale parameter) is identified on the basis of regression curves defined for the USCB region. The estimation of the second parameter (the mean apparent wave passage velocity) is based on discrete experimental data acquired via the vibroseis excitation registered in the in situ experiment. The impact of the model application on the dynamic performance of the bridge is assessed by comparing the dynamic response levels under SMIKE excitations, classic uniform excitations, and the “traveling wave” model—accounting only for the wave passage effect. The influence of wave velocity occurs to be crucial, modifying (either amplifying or reducing, depending on the location of the analyzed point) the dynamic response level up to a factor of two. The introduction of the space scale parameter changes the results by 20% in relation to the outcomes obtained for the “traveling” wave only.

The Characteristics and Variability of Intraseasonal Coastal Kelvin Waves in the Bay of Bengal under Hindcast Conditions and the RCP8.5 Scenario

Abstract The characteristics and variability of intraseasonal internal coastal Kelvin waves (CKWs) along the Bay of Bengal (BoB) waveguide are investigated in the context of global warming by employing a regional ocean model. The analyzed period covers 120 years from 1980 to 2099, which includes the historical scenario and the RCP8.5 scenario. CKW information is successfully extracted from the temperature anomalies along the pycnocline by applying a newly developed methodology. The analysis reveals that intraseasonal CKWs in the BoB are highly in accordance with the intraseasonal zonal wind stress in the western equatorial Indian Ocean; the downwelling CKW lags the equatorial intraseasonal westerly winds, and the upwelling CKW lags the equatorial intraseasonal easterly winds. The CKWs significantly affect subsurface characteristics at the eastern BoB boundary, and the weakening of CKWs near the Irrawaddy Delta tip is a general feature occurring in the subsurface. With respect to the long-term scale, the occurrence of significant CKWs is predicted to be more frequent in the future under the high emissions pathway. Remarkably, the monthly climatology of CKWs varies over time; unlike the first two 30-yr analyzed periods, significant CKWs are predicted to mainly occur around August during the last two 30-yr periods due to the corresponding variabilities in the equatorial wind field, suggesting that the BoB characteristics may greatly deviate from the current climatological state.

Identification of Solid-State Wave Gyroscopes Resonator Mechanical Errors in the Mode of Free Run-out of Standing Waves

To improve the accuracy of the output signals of solid-state wave integrating gyroscopes, various options for algorithms to identify mechanical errors of their resonators in the mode of occasionally switched mode of standing waves free run-out are considered. The measured physical parameters selected are: multi-frequency, Q factor and multi-potency, viscosity axes and stiffness axes of gyroscope resonators. Most algorithms are designed for methods of resonator mechanical errors production control and include the following stages: swinging a standing wave in the selected angular direction; circuit cut off of its active excitation; signal recording and analysis within two axes of measuring device; identification of mathematical model parameters for standing waves, recorded in their slowly changing amplitudes. Additionally, to search for stiffness axes, a technique with adjustable gyroscope resonator rotation axis is given. As a mathematical basis for the derivation and justification of the proposed identification algorithms, the necessary theoretical dependencies are given, explaining the processes of formation and processing the internal measuring signals in solid-state wave gyroscopes. As a practical testing of the most common identification technique, a laboratory study of one technological specimen of a quartz hemispherical gyroscope resonator was performed. To measure its free oscillations, a measuring system of the balancing stand was used, with measurement error up to 1% and a means of analog signals measurment, with an error of 0.05% when measuring a DC voltage of 10V. The experiment carried out showed the effective use of electrode excitation lines of standing wave for four angles {0°, 22.5°, 45°, 67.5°}. At the same time, the measurement time at each angular position was 60 seconds, and the sampling frequency of a separate measuring channel was 33,333 Hz. Herewith, each value of the wave variables was identified at 340 periods of resonant oscillations.

A global ensemble of ocean wave climate statistics from contemporary wave reanalysis and hindcasts

There are numerous global ocean wave reanalysis and hindcast products currently being distributed and used across different scientific fields. However, there is not a consistent dataset that can sample across all existing products based on a standardized framework. Here, we present and describe the first coordinated multi-product ensemble of present-day global wave fields available to date. This dataset, produced through the Coordinated Ocean Wave Climate Project (COWCLIP) phase 2, includes general and extreme statistics of significant wave height (Hs), mean wave period (Tm) and mean wave direction (θm) computed across 1980–2014, at different frequency resolutions (monthly, seasonally, and annually). This coordinated global ensemble has been derived from fourteen state-of-the-science global wave products obtained from different atmospheric reanalysis forcing and downscaling methods. This data set has been processed, under a specific framework for consistency and quality, following standard Data Reference Syntax, Directory Structures and Metadata specifications. This new comprehensive dataset provides support to future broad-scale analysis of historical wave climatology and variability as well as coastal risk and vulnerability assessments across offshore and coastal engineering applications.

Wave resource spatial and temporal variability dependence on WEC size

As the wave energy sector grows and looks to the Blue Economy for commercialization opportunities, there is a distinct and pressing need to clearly understand and quantify the coupled impacts of wave energy converter (WEC) size and wave resource characteristics on the annual energy production, spatial variability and temporal variability. Utilizing generic frequency domain representations of the Oscilla Power Triton WEC and spectral wave conditions at PacWave (Oregon), Los Angeles (California) and WETS (Hawaii), a series of interesting results emerge. Firstly, the ‘optimal’ WEC size, from an energy standpoint, is fundamentally dependent on the frequency distribution of the incoming wave variance density spectrum. Secondly, and from a seasonality perspective, the seasonal WEC energy generation doesn’t necessarily follow the seasonal distribution of gross wave power. Finally, from an hourly power variability perspective, a reduction in WEC size generally decreases variability. However, for each of the locations investigated, there appears to be a WEC size threshold; a threshold where further reducing WEC size results in increased power variability.

RETRACTED: On an efficient approach to solutions of a perturbed nonlinear Schrödinger's equation

The main objective of this paper is to retrieve the analytical solutions for a perturbed nonlinear Schrödinger’s equation. These achievements are obtained by following the basic steps of an efficient approach. The method we have used for the model is a completely novel and powerful technique that has not been used for the model so far. The basic common idea of the method is to convert the structure of the equation from a partial differential equation to an ordinary one using a new soliton wave variable. During the implementation of these methods, a variety of explicit solutions for different structures are extracted. For the sake of better understanding the dynamics of the solutions, several diagrams related to the introduced solutions are also plotted. We conclude that the employed method is an efficient tool for solving partial differential equations that paves the way to solve other practical models in the field. The software used in this article is Wolfram Mathematica.

Approach to T wave Variability

Approach to T wave Variability

The canine T wave: a retrospective analysis on qualitative and quantitative T wave variables obtained in 129 healthy dogs and proposed reference intervals

Introduction/objectiveThe T wave is a poorly characterized electrocardiographic variable in small animals. Therefore, this study aimed to describe T wave features in a large population of healthy dogs. Animals, materials, and methodsMedical records were reviewed to identify healthy dogs ≥one-year-olds that underwent an electrocardiogram. T wave qualitative (morphology, polarity, and concordance between R and T waves) and quantitative (duration, amplitude, mean electrical axis, ratio between T and R waves amplitudes, interval from the peak to the end of the T wave, and ratio between the duration of the latter interval and that of the QT) variables were evaluated. Continuous and categorical variables were compared between dogs of distinct sex, body weight (BW), age and somatotype using the Mann–Whitney U test and χ2 test, respectively. Spearman's correlation coefficients between quantitative variables and age and BW were calculated. Reference intervals of quantitative variables were determined in the overall population. ResultsOne hundred and twenty-nine dogs were enrolled. Concerning morphology, the asymmetrical (slow/fast) pattern occurred more frequently than the symmetrical and biphasic ones. Concerning polarity, positive T waves occurred more frequently than negative and neutral ones. T and R waves were predominantly concordant. No meaningful differences were found when comparing qualitative and quantitative variables between dogs of distinct sex, BW, age and somatotype. No significant correlations were found between quantitative variables and age and BW. Reference intervals of quantitative variables are provided. ConclusionsCanine T wave features were addressed and statistically reliable reference intervals made available for clinical use.