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Waves critically modulate the air‐sea fluxes, and upper‐ocean thermodynamics in a Tropical Cyclone (TC) system. This study improves the modeling of TC intensification by incorporating non‐breaking wave‐induced turbulence and sea spray from breaking waves into an atmosphere‐ocean‐wave coupled model. Notably, wind forecast error decreased by around 10% prior to TCs' peak intensity. The positive feedback of sea spray along with compensatory negative feedback from non‐breaking waves, overall enhanced TCs' intensity. These breaking and non‐breaking wave‐coupled processes consistently cool sea surface temperature, resulting in improvement of the modeled SST. Observed improvements in full‐year TC cases ranging from Categories I to IV in this study suggest that an accurate characterization of ocean wave‐coupled processes is crucial for improving TCs' intensity forecasts and advancing our understanding of severe weather events in both, the atmosphere and ocean. Plain Language Summary: Tropical Cyclones (TCs), such as hurricanes and typhoons, are destructive natural disasters that can cause extensive damage. Our study focused on understanding the role of ocean waves and related processes in TCs. Through numerical modeling, we found that ocean waves, specifically breaking and non‐breaking waves, have a substantial influence on TCs' intensity. Breaking waves contribute positively through the production of sea spray droplets, while non‐breaking wave‐induced turbulence has a compensatory negative effect, resulting in an enhancement in TCs' intensity. Incorporating both wave mechanisms into the models improved the accuracy of TCs' intensity and their underlying sea surface temperature. By highlighting the importance of ocean wave‐coupled physics, we aim to enhance our understanding of TCs and improve disaster preparedness to mitigate their impacts on coastal communities. Key Points: Full‐year regional hindcast of Tropical Cyclones (TCs) at the North West AustraliaInclusion of wave‐coupled processes improves TCs modeling, by reducing forecast errors and enhancing rapid intensification simulationsSea spray increases TC development while nonbreaking wave turbulence has the opposite effect with the first process dominating [ABSTRACT FROM AUTHOR]

When a wave breaks, it produces bubbles whose sizes depend on the breaking severity. This paper attempts to estimate wave breaking dissipation through a passive acoustic method. Initially, regular waves were forced to break in a flume. The breaking energy loss (severity) and the underwater acoustic noise were recorded. Two kinds of thresholds, in terms of sound wave amplitude and the ratio of sound wave height to period, respectively, were used together to identify the sound waves generated by newly formed bubbles. The frequencies of these sound waves are connected with the bubble sizes. Thus, a relationship between the mean bubble radius and the breaking severity was established and found to be linear. This laboratory relationship was then applied to Lake George data to study the breaking dissipation rate across the spectrum. An average acoustic spectral density threshold was proposed to identify breaking events from acoustic records in the field. The sound waves associated with bubble formation were selected by means of the same two kinds of threshold as used in the laboratory. Thus, the mean bubble radius of each breaking event was obtained and translated into the breaking severity. The values of experimental dissipation were compared with previous relevant results obtained through different methods as well as the wave breaking dissipation source terms ST6 (WAVEWATCH-III model) and are in good agreement with both of them. [ABSTRACT FROM AUTHOR]

Waves and sea ice form a closely coupled system: waves govern sea ice through stress, floe break‐up, and wave‐induced currents, while sea ice affects waves through attenuation and reflection. Wave‐induced sea ice break‐up is particularly important as it can regulate air‐sea interaction and consequently also regulate the growth and melt of sea ice. This coupled nature is complex and generally, especially at the large scale, neglected in modeling of the polar climate system. Here, we explore a novel way of coupling through wave‐induced ice break‐up, and conduct a case study for the Antarctic summer of 2019/2020. Our modeling approach builds upon previous investigations as follows: (a) sea ice takes a binary form, either "broken" or "unbroken," (b) waves may break sea ice, transitioning it from unbroken to broken, (c) a threshold separating breaking and nonbreaking wave fields is used to identify when this occurs, (c) two modes of attenuation for waves in ice (dependent upon the ice state), representing the observed on/off switch in wave attenuation. By characterizing wave attenuation and sea ice break‐up as described above, we achieve two‐way wave‐sea ice coupling, thereby allowing wave‐sea ice feedbacks. This model is limited to the ice‐melt season as refreeze is not represented here. We demonstrate that our model can simulate both the wavefield in and the evolution of the Marginal Ice Zone. Our results show the validity of empirically derived wave‐induced sea ice break‐up threshold, and substantiate that waves have a critical influence on the morphology of the Marginal Ice Zone. Plain Language Summary: The interactions between waves and sea ice are complex and, when represented in numerical models, often over‐simplified or even neglected. For example, waves act very differently in regions covered by small ice floes or broken ice compared to those covered by an unbroken cover of very large ice floes. Wave dissipation can differ by orders of magnitude, but wave‐forecast models usually try to find some "effective" parameters for their attenuation modules valid on average in both environments. Even more, sufficiently large waves can break the ice, thereby changing the behavior of waves in this region. Sea ice forms a crucial barrier between air and sea, and understanding when and how it breaks is crucial to understanding polar regions. Here, we introduce and test a simple yet effective model of wave‐ice interaction. Our results show that waves have a critical influence on evolution of sea ice, and are essential to understanding polar regions. Key Points: A new model of wave‐sea ice interaction, with coupling achieved through wave‐induced sea ice break‐up based on a nondimensional thresholdThe model is able to capture the position of the unbroken sea ice front and individual break‐up eventsThe ability of this simple wave model indicates that waves may have a critical influence on Marginal Ice Zone morphology [ABSTRACT FROM AUTHOR]

The CO2 gas transfer velocity ( K CO 2 ) at air–sea interface is usually parameterized with the wind speed, but to a great extent it is defined by waves and wave breaking. To investigate the direct relationship between K CO 2 and waves, laboratory experiments are conducted in a wind-wave flume. Three types of waves are forced in the flume: modulational wave trains generated by a wave maker, wind waves with 10-m wind speed ranging from 4.5 to 15.5 m s−1, and (mechanically generated) modulational wave trains coupled with superimposed wind force. The wave height and wave orbital velocity are found to be well correlated with K CO 2 whereas wind speed alone cannot adequately describe K CO 2 . To reconcile the measurements, nondimensional equations are established in which gas transfer velocity is expressed as a main function of wave parameters and an additional secondary factor to account for influence of the wind. [ABSTRACT FROM AUTHOR]

Laboratory experiments were performed to investigate the effects of a coflowing current field on the spectral shape of water waves. The results indicate that refraction is the main factor in modulating wave height and overall wave energy. Although the structure of the current field varies considerably, some current-induced patterns in the wave spectrum are observed. In high frequencies, the energy cascading generated by nonlinear interactions is suppressed, and the development of a spectral tail is disturbed, as a consequence of the detuning of the four-wave resonance conditions. Furthermore, the presence of currents slows the downshifting of the spectral peak. The suppression of the high-frequency energy under the influence of currents is more prominent as the spectral steepness increases. The energy suppression is also more accentuated and long-standing along the fetch when the directional spreading of waves is sufficiently broad. This result indicates that the current-induced detuning of resonant conditions is more effective when exact resonances are the primary mechanism of nonlinear interactions than when quasi resonances prevail (directionally narrow cases). Additionally, the directional analysis shows that the highly variable currents broaden the directional spreading of waves. The broadening is suggested to be related to random refraction and scattering of wave rays. The random disturbance of wavenumbers alters the nonlinear interaction conditions and weakens the energy exchanges among wave components, which is expressed in the suppression of the high-frequency energy. [ABSTRACT FROM AUTHOR]

Progression of nonlinear wave groups to breaking was studied numerically and experimentally. Evolution of such wave group parameters as a function of distance to breaking and modulation depth-the height ratio of the highest and the lowest waves in the group-was described. Numerical model results demonstrated good agreement with experimental results in describing the behavior of the distance to breaking and modulation depth as functions of initial wave steepness. It was shown that energy loss appears to be a function of the modulation depth at the breaking onset. Energy loss grows with modulation depth up to a certain threshold of the latter. It was also shown that breaking probability for wave groups with modulation depth below 2.2 is very low. [ABSTRACT FROM AUTHOR]

New parameterizations for the spectral dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observations of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is nonzero only when a nondimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short-wave dissipation is introduced to represent the dissipation of short waves due to longer breaking waves. A reduction of the wind-wave generation of short waves is meant to account for the momentum flux absorbed by longer waves. These parameterizations are combined and calibrated with the discrete interaction approximation for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but, overall, the parameterizations probably yield the most accurate estimates of wave parameters to date. Perspectives for further improvement are also given. [ABSTRACT FROM AUTHOR]

This paper is dedicated to wave-induced turbulence unrelated to wave breaking. The existence of such turbulence has been foreshadowed in a number of experimental, theoretical, and numerical studies. The current study presents direct measurements of this turbulence. The laboratory experiment was conducted by means of particle image velocimetry, which allowed estimates of wavenumber velocity spectra beneath monochromatic nonbreaking unforced waves. Observed spectra intermittently exhibited the Kolmogorov interval associated with the presence of isotropic turbulence. The magnitudes of the energy dissipation rates due to this turbulence in the particular case of 1.5-Hz deep-water waves were quantified as a function of the surface wave amplitude. The presence of such turbulence, previously not accounted for, can affect the physics of the wave energy dissipation, the subsurface boundary layer, and the ocean mixing in a significant way. [ABSTRACT FROM AUTHOR]

Nearly all of the momentum transferred from wind to waves comes about through wave-induced pressure acting on the slopes of waves: known as form drag. Direct field measurements of the wave-induced pressure in airflow over water waves are difficult and consequently rare. Those that have been reported are for deep water conditions and conditions in which the level of forcing, measured by the ratio of wind speed to the speed of the dominant (spectral peak) waves, is quite weak, U10/cc < 3. The data reported here were obtained over a large shallow lake during the Australian Shallow Water Experiment (AUSWEX). The propagation speeds of the dominant waves were limited by depth and the waves were correspondingly steep. This wider range of forcing and concomitant wave steepness revealed some new aspects of the rate of wave amplification by wind, the so-called wind input source function, in the energy balance equation for wind-driven water waves. It was found that the exponential growth rate parameter (fractional energy increase per radian) depended on the slope of the waves, ak, vanishing as ak → 0. For very strong forcing a condition of "full separation" occurs, where the airflow detaches from the crests and reattaches on the windward face leaving a separation zone over the leeward face and the troughs. In a sense, the outer flow does not "see" the troughs and the resulting wave-induced pressure perturbation is much reduced, leading to a reduction in the wind input source function relative to that obtained by extrapolation from more benign conditions. The source function parameterized on wave steepness and degree of separation is shown to be in agreement with previous field and laboratory data obtained in conditions of much weaker forcing and wave steepness. The strongly forced steady-state conditions of AUSWEX have enabled the authors to define a generalized wind input source function that is suitable for a wide range of conditions. [ABSTRACT FROM AUTHOR]

Computational Fluid Dynamics (CFD) is used to numerically simulate the viscous air-water flow around a thin rigid floating plate subjected to surface waves, with the aim to improve the understanding of dissipative mechanisms in drifting and non-drifting conditions. CFD model is validated by comparing the obtained results against previously published data of Nelli et al. (2017). It is shown that the energy of the waves is dissipated by the water flow over both upper and lower surfaces of the plate. The dissipation increases as a function of steepness of incoming waves. On the upper surface of the non-drifting plate, overwash contributes to dissipation of the energy of steep waves, while this effect is slightly smaller when the plate is moving freely. Simple equations are used for estimating the overwash height and energy fluxes, which are found to be in fair agreement with the present CFD simulations. The energy dissipation due to the shear stresses under the surface of the plate is seen to be higher when the body is drifting in the longitudinal direction. Equations for the energy dissipation under the plate are also formulated, and are observed to follow the results of the present CFD simulations. • Water wave interaction with drifting and non-drifting rigid thin plates is modeled using a CFD model. • Energy is shown to be dissipated on the upper and lower surfaces of the plate. • Steeper waves are shown found to dissipated up to 20% of the energy of incoming wave. • Parameterisations are developed to compute energy dissipation, which are found to be accurate. [ABSTRACT FROM AUTHOR]

The identification of quiescent periods in oceans and regional waters is an important task that ensures safer operations in the marine environment. If such identification is done through a probabilistic approach on a geographical scale, it can be used for quick planning of search and rescue operations. This paper aims to present a simple equation that can be universally used for calculating the waiting time for a desired quiescent period to emerge. This is achieved through monitoring various low-run waves occurring in different sea states. The related data is numerically generated using a high fidelity code that permits the fully nonlinear solution of water waves propagating in a computational domain under nonlinear conditions set for the upper layer of the fluid. The probability distributions of quiescent runs are found and then formulated using a modified geometric distribution function. This function is identified by one parameter. The subtraction of this parameter from unity is equivalent to the probability of two successive low waves. This parameter is observed to decrease with an increase in the wave height threshold and is found to be nearly insensitive to variables representing sea states. An equation is established for calculating the parameter used in the calculation of quiescent period probabilities. The probability curves of quiescent runs constructed using a geometric distribution function are observed to be in fair agreement with those found in the numerical data. The suggested method for calculating quiescent period probabilities is straightforward and can be easily used to compute the waiting time for desired quiescent periods on a geographical scale. • Low-run events of different directional sea states are identified. • The probability of quiescent periods is monitored. • A simple method is developed that provides the probability of quiescent runs. • The method is very easy to use and can provide the waiting time for a desired quiescent period to occur on a geographical scale, which can be used for detailed planning of search and rescue operations in a targeted region. [ABSTRACT FROM AUTHOR]

We have investigated the dispersion of tracer particles by numerically simulating ensemble nonlinear gravity waves on the surface of an infinitely deep fluid. Using the concepts of passive Lagrangian markers and insights from weak wave turbulence theory, we validated fundamental predictions for particle kinematics associated with scaling laws and probability density functions. These results improve the understanding of wave-driven transport phenomena that depart far from equilibrium and the development of the high-fidelity models of transport processes in geophysical systems. • Dispersion of particles by nonlinear water waves has been investigated numerically. • Predictions of the Weak Wave Turbulence Theory have been confirmed. • The self-similarity form for Probability Density Function has been validated. [ABSTRACT FROM AUTHOR]

Breathers are exact solutions of the uni-directional nonlinear Schrödinger equation (NLS) andare known to describe the spatio-temporal dynamics of rogue waves in the context ofmodulation instability. We report observations of slanted localized envelope soliton andbreather dynamics in a directional water wave basin. The water surface displacement hasbeen stereo-reconstructed using a marker-net, deployed at the center of the basin, and twosynchronized high-speed cameras. The results are in very good agreement with thehyperbolic 2D+1 NLS predictions and confirm that short-crested as well as oblique localizedwaves can be indeed described by a simplified nonlinear hydrodynamic framework. [ABSTRACT FROM AUTHOR]