Wave breaking represents one of the most interesting and challenging problems for fluid mechanics and physical oceanography. Over the last 15 years our understanding has undergone a dramatic leap ...forward, and wave breaking has emerged as a process whose physics is clarified and quantified. Ocean wave breaking plays the primary role in the air-sea exchange of momentum, mass and heat, and it is of significant importance for ocean remote sensing, coastal and ocean engineering, navigation and other practical applications. This book outlines the state of the art in our understanding of wave breaking and presents the main outstanding problems. It is a valuable resource for anyone interested in this topic: researchers, modellers, forecasters, engineers and graduate students in physical oceanography, meteorology and ocean engineering.
The Wave Climate of the Southern Ocean Young, Ian R.; Fontaine, Emmanuel; Liu, Qingxiang ...
Journal of physical oceanography,
05/2020, Letnik:
50, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Abstract
The wave climate of the Southern Ocean is investigated using a combined dataset from 33 years of altimeter data, in situ buoy measurements at five locations, and numerical wave model ...hindcasts. The analysis defines the seasonal variation in wind speed and significant wave height, as well as wind speed and significant wave height for a 1-in-100-year return period. The buoy data include an individual wave with a trough to crest height of 26.4 m and suggest that waves in excess of 30 m would occur in the region. The extremely long fetches, persistent westerly winds, and procession of low pressure systems that traverse the region generate wave spectra that are unique. These spectra are unimodal but with peak frequencies that propagate much faster than the local wind. This situation results in a unique energy balance in which waves at the spectra peak grow as a result of nonlinear transfer without any input from the local wind.
Indonesia is an archipelago country with great potential for marine renewable energy, particularly for wave energy. This study will provide a wave energy assessment of Indonesia over a 6.5-year ...period (2011–2017) with resolution about 5.5 km. This assessment is based on data generated with a two-way nested high-resolution wave model WAVEWATCH III with observation-based physics (ST6). Three grids have been generated, namely a ‘high resolution’ of 3 arc-minute (0.05°) grid is nested inside a 12 arc-minute (0.2°) grid which is nested within a 0.5° global grid. Validations against altimeters and buoys show good agreement with the model. Mean wave energy has been classified based on meteorological seasons and it is found that the most energetic months are June, July, August for all areas of south, southwest and west of Indonesia where it can exceed 30 kW/m. In some locations wave energy is available throughout the entire year, that is in the south of Jawa island, Bali island and West Nusa Tenggara while in the region of west Sumatera, promising wave energy is available during the time from March to November. In addition, within the Indonesian Archipelago the monthly variations are about 5 kW/m and relatively small in terms of absolute values but this region is large relative to the mean wave power energy.
•Wave energy assessment for Indonesian archipelago with spatial resolution of 0.05°.•Based on a dynamically downscaled wave model with observation-based physics (ST6).•Mean wave power in excess of 30 kW/m was found for season June to August.•10% of mean wave power exceeds 40 kW/m with the top-one percent up to 60 kW/m.
•New nonlinear wind input source term.•Negative wind input for adverse winds.•New wave breaking and whitecapping dissipation source term.•New swell attenuation source term.
Measurements collected ...during the AUSWEX field campaign, at Lake George (Australia), resulted in new insights into the processes of wind wave interaction and whitecapping dissipation, and consequently new parameterizations of the input and dissipation source terms. The new nonlinear wind input term developed accounts for dependence of the growth on wave steepness, airflow separation, and for negative growth rate under adverse winds. The new dissipation terms feature the inherent breaking term, a cumulative dissipation term and a term due to production of turbulence by waves, which is particularly relevant for decaying seas and for swell. The latter is consistent with the observed decay rate of ocean swell. This paper describes these source terms implemented in WAVEWATCH III ®and evaluates the performance against existing source terms in academic duration-limited tests, against buoy measurements for windsea-dominated conditions, under conditions of extreme wind forcing (Hurricane Katrina), and against altimeter data in global hindcasts. Results show agreement by means of growth curves as well as integral and spectral parameters in the simulations and hindcast.
R/V Lance serendipitously encountered an energetic wave event around 77°N, 26°E on 2 May 2010. Onboard GPS records, interpreted as the surface wave signal, show the largest waves recorded in the ...Arctic region with ice cover. Comparing the measurements with a spectral wave model indicated three phases of interaction: (1) wave blocking by ice, (2) strong attenuation of wave energy and fracturing of ice by wave forcing, and (3) uninhibited propagation of the peak waves and an extension of allowed waves to higher frequencies (above the peak). Wave properties during fracturing of ice cover indicated increased groupiness. Wave‐ice interaction presented binary behavior: there was zero transmission in unbroken ice and total transmission in fractured ice. The fractured ice front traveled at some fraction of the wave group speed. Findings do not motivate new dissipation schemes for wave models, though they do indicate the need for two‐way, wave‐ice coupling.
Key Points
Largest waves measured under ice cover in the Arctic
High‐resolution, coupled wave‐ice models are required for accurate predictions
Nonlinearly enhanced waves may lead to initial ice breakup
Twenty years (1996–2015) of satellite observations were used to study the climatology and trends of oceanic winds and waves in the Arctic Ocean in the summer season (August–September). The ...Atlantic-side seas, exposed to the open ocean, host more energetic waves than those on the Pacific side. Trend analysis shows a clear spatial (regional) and temporal (interannual) variability in wave height and wind speed. Waves in the Chukchi Sea, Beaufort Sea (near the northern Alaska), and Laptev Sea have been increasing at a rate of 0.1–0.3 m decade−1, found to be statistically significant at the 90% level. The trend of waves in the Greenland and Barents Seas, on the contrary, is weak and not statistically significant. In the Barents and Kara Seas, winds and waves initially increased between 1996 and 2006 and later decreased. Large-scale atmospheric circulations such as the Arctic Oscillation and Arctic dipole anomaly have a clear impact on the variation of winds and waves in the Atlantic sector. Comparison between altimeter observations and ERA-Interim shows that the reanalysis winds are on average 1.6 m s−1 lower in the Arctic Ocean, which translates to a low bias of significant wave height (−0.27 m) in the reanalysis wave data.
In spite of massive efforts directed to development of climate models over recent decades, accurate climate simulations and prediction remain a grand challenge. Large sea surface temperature model ...bias is one of the key indicators of the problem, among others. Qiao and his team suggested the concept of surface wave‐induced turbulence and elaborated the way for such coupling, through turbulent processes at both sides of the air‐ocean interface. These are the wave mixing in the ocean and wave modulation of air‐sea fluxes. This wave‐ocean coupled approach led to essential improvements of performance of ocean circulation and climate models, essentially introducing the next generation of large‐scale air‐sea interaction models. This Commentary reviews three recent JGR publications where the Qiao theory was implemented. The first paper (Huang & Qiao, 2021; https://doi.org/10.1029/2020JC016839) reported that the momentum gain by the ocean could be larger than the wind stress input, due to the ocean waves. The second paper (Chen et al., 2022; https://doi.org/10.1029/2021JC018360) demonstrated that, also due to waves, the drag coefficients in the atmospheric boundary layer have a spatial asymmetry during tropical cyclones. The third paper (Zhao et al., 2022; https://doi.org/10.1029/2022JC019015), based on combination of wave‐coupled effects on both sides of air‐sea interface, demonstrates their impact on simulation of tropical cyclone intensity. All papers are based on unique in situ measurements and their data analysis. The Commentary is further used as an opportunity to outline and review the current state of the small‐large scale coupling topic with respect to ocean, weather and climate modeling.
Plain Language Summary
Understanding the nature of climate change and predicting its trends have been one of the highest priorities for scientific communities and of great importance for the public. Climate simulations, however, have been facing challenges which persist for decades, and apparently mean that some of the physical processes in their description are missing. A large set of such processes rest with the coupled nature of small‐ and large‐scale air‐sea interaction phenomena. Since the spatio‐temporal scales of surface waves, around 100 m and 10 s, are too far from those in the climate system, that is, thousands to tens thousands kilometers and years to decades, their coupling have never been incorporated by climate models due to lack of understanding of physics of such interactions and computing capabilities. Recent publications indicate that surface waves can both change the upper ocean through non‐breaking wave‐induced mixing and, on the atmospheric side, air‐sea fluxes through modulating the interface of ocean and atmosphere. As a result, ocean and climate predictions can be essentially improved by considering surface waves in climate models. The Commentary mainly discusses three recent papers dedicated to this topic.
Key Points
This Commentary reviews three recent JGR publications dedicated to wave‐coupled approaches to large‐scale air‐sea systems
This wave‐ocean coupled approach led to essential improvements of performance of ocean circulation and climate models
The Commentary is further used as an opportunity to outline and review the current state of the small‐large scale coupling topic
Abstract
The observation-based source terms available in the third-generation wave model WAVEWATCH III (i.e., the ST6 package for parameterizations of wind input, wave breaking, and swell dissipation ...terms) are recalibrated and verified against a series of academic and realistic simulations, including the fetch/duration-limited test, a Lake Michigan hindcast, and a 1-yr global hindcast. The updated ST6 not only performs well in predicting commonly used bulk wave parameters (e.g., significant wave height and wave period) but also yields a clearly improved estimation of high-frequency energy level (in terms of saturation spectrum and mean square slope). In the duration-limited test, we investigate the modeled wave spectrum in a detailed way by introducing spectral metrics for the tail and the peak of the omnidirectional wave spectrum and for the directionality of the two-dimensional frequency–direction spectrum. The omnidirectional frequency spectrum
E
(
f
) from the recalibrated ST6 shows a clear transition behavior from a power law of approximately
f
−4
to a power law of about
f
−5
, comparable to previous field studies. Different solvers for nonlinear wave interactions are applied with ST6, including the Discrete Interaction Approximation (DIA), the more expensive Generalized Multiple DIA (GMD), and the very expensive exact solutions using the Webb–Resio–Tracy method (WRT). The GMD-simulated
E
(
f
) is in excellent agreement with that from WRT. Nonetheless, we find the peak of
E
(
f
) modeled by the GMD and WRT appears too narrow. It is also shown that in the 1-yr global hindcast, the DIA-based model overestimates the low-frequency wave energy (wave period
T
> 16 s) by 90%. Such model errors are reduced significantly by the GMD to ~20%.
The surface waves investigation and monitoring (SWIM) instrument onboard the China-France Oceanography Satellite (CFOSAT) can retrieve directional wave spectra with a wavelength range of 70-500 m. ...This study aims to validate the partitioned integrated wave parameters (PIWPs) from SWIM, including partitioned significant wave height (PSWH), partitioned peak wave period (PPWP), and partitioned peak wave direction (PPWD), against those from National Data Buoy Center (NDBC) buoys. With quasi-simultaneous spectra from two NDBC buoys 13 km away from each other near Hawaii, the methods of comparing PIWPs from two sets of spectra were discussed first. After cross-assigning partitions according to the spectral distance, it is found that wrong cross-assignments lead to many outliers strongly impacting the estimate of error metrics. Three methods, namely comparing only the best-matched partition, changing the threshold of spectral distance during cross-assignment, and maximum likelihood estimation of root-mean-square error (RMSE) of PIWPs, were used to reduce the impact of potential wrong cross-assignments. Using these methods, the SWIM PIWPs were validated against NDBC buoys. The results show that SWIM performs well at finding the spectral peaks of different partitions with the RMSE of PPWPs and PPWDs of 0.9 s and 20°, respectively, which can be a useful complement for other wave observations. However, the accuracy of PSWH from SWIM is not that good at this stage, probably because the high noise level in the spectra impacts the result of the partitioning algorithm. Further improvement is needed to obtain better PSWH information.
Accurate quantification of air-sea gas transfer velocity is critical for our understanding of air-sea CO2 gas fluxes, global carbon budget and climate responses. CO2 transfer velocity is ...predominantly subject to constraints of wave-related dynamic processes at the ocean surface layer but is typically parameterized with wind speed. This study proposes and compares two parameterizations which accommodate dimensionless wave terms. The validations are conducted using both laboratory and field measurements of CO2 transfer and wave statistics. A scaling of bubble-mediated gas transfer is implemented into the formula that is linked to wave breaking probability. The improved parameterizations are capable of collapsing combined laboratory and field data sets which comprise diversified conditions of wind, wave and wave breaking.
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