Strip segmentation of oceanic internal waves in SAR images based on TransUNet

The development of oceanic remote sensing artificial intelligence has made possible to obtain valuable information from amounts of massive data.Oceanic internal waves play a crucial role in oceanic activity.To obtain oceanic internal wave stripes from synthetic aperture radar(SAR)images,a stripe segmentation algorithm is proposed based on the TransUNet framework,which is a combination of U-Net and Transformer,which is also optimized.Through adjusting the number of Transformer layer,multi-layer perceptron(MLP)channel,and Dropout parameters,the influence of over-fitting on accuracy is significantly weakened,which is more conducive to segmenting lightweight oceanic internal waves.The results show that the optimized algorithm can accurately segment oceanic internal wave stripes.Moreover,the optimized algorithm can be trained on a microcomputer,thus reducing the research threshold.The proposed algorithm can also change the complexity of the model to adapt it to different date scales.Therefore,TransUNet has immense potential for segmenting oceanic internal waves.

INSTABILITY OF THE OCEANIC WAVES IN THE TROPICAL REGION

In this paper, the effects of the large-scale mean sea temperature fields of the tropical ocean and the zonal current field (southern equatorial current) have been comprehensively entered in consideration on the basis of Chao and Ji (1985), and Ji and Chao (1986), the equatorial oceanic waves of the tropical ocean have been discussed by use of linearized primitive equations, then, the significant influence of the climatic back- ground fields of the tropical ocean upon the oceanic waves of this region has been further testified. When very cold water appears in the tropical region, and the southern equatorial current is also relatively strong, the effect of the Rossby wave weakens, as a consequence, there are substitutive slow waves (i.e. thermal waves) which travel in opposite direction (eastward) to the Rossby wave. The characteristics of the slow wave are similar to those of Rossby waves, only the travelling direction is opposite. Under a certain environ- mental background field, the slow wave and the modified Rossby wave may be instable. With this conclu- sion, the mechanism of the occurrence, development and propagation of El Nino events has been studied. It is pointed out that the opposite travelling direction of the thermal wave and Rossby wave will bring re- pectively into action under different marine environmental background fields. The physical causes for that the abnormal warm water inclines to occur along the South American coast have also been explored in this paper.

On the Variability of Charleston South Carolina Winds, Atmospheric Temperatures, Water Levels, Waves and Precipitation

Atmospheric winds, air temperatures, water levels, precipitation and oceanic waves in the Charleston South Carolina (SC) coastal zone are evaluated for their intrinsic, internal variability over temporal scales ranging from hours to multi-decades. The purpose of this study was to bring together a plethora of atmospheric and coastal ocean state variable data in a specific locale, to assess temporal variabilities and possible relationships between variables. The questions addressed relate to the concepts of weather and climate. Data comprise the basis of this study. The overall distributions of atmospheric and coastal oceanic state variable variability, including wind speed, direction and kinematic distributions and state variable amplitudes over a variety of time scales are assessed. Annual variability is shown to be highly variable from year to year, making arithmetic means mathematically tractable but physically meaningless. Employing empirical and statistical methodologies, data analyses indicate the same number of intrinsic, internal modes of temporal variability in atmospheric temperatures, coastal wind and coastal water level time series, ranging from hours to days to weeks to seasons, sub-seasons, annual, multi-year, decades, and centennial time scales. This finding demonstrates that the atmosphere and coastal ocean in a southeastern U.S. coastal city are characterized by a set of similar frequency and amplitude modulated phenomena. Kinematic hodograph descriptors of atmospheric winds reveal coherent rotating and rectilinear particle motions. A mathematical statistics-based wind to wave-to-wave algorithm is developed and applied to offshore marine buoy data to create an hour-by-hour forecast capability from 1 to 24 hours;with confidence levels put forward. This affects a different approach to the conventional deterministic model forecasting of waves.

On generation source sites of internal waves in the Luzon Strait

This effort aims to determine the generation source sites in the Luzon Strait for energetic, long-crest, transbasin internal waves （IW） observed in the northern South China Sea （NSCS）. The roles of islands distributed on eastern side of the strait, Kuroshio, submarine ridges, shoaling thennocline, and strait configuration played in the IW generation are examined using the cruise data analysis, satellite data interpretation, and dynamical analysis. The islands and channels on eastern side of the strait are excluded from a list of possible IW source sites owing to their unmatched horizontal dimensions to the scale of IW crest line length, and the relative low Reynolds number. The Kuroshio has a potential to be a radiator for the long-crest IW disturbances, meanwhile, the Kurosbio west （east） wing absorbs the eastward （westward） propagating IW disturbance. Namely, the Kuroshio blockades the outside west-east propagating IW disturbances. The 3-D configuration of the Luzon Strait is characterized by a sudden, more than one order widening of the cross-section areas at the outlets on both sides, providing a favorable condition for IW type initial disturbance formation. In the Luzon Strait, the thermocline is featured by a westward shoaling all the year around, providing the dynamical conditions for the amplitude growth （declination） to the westward （eastward） propagating IW type disturbance. Thus, the west slope of western submarine ridge at the western outlet of the Luzon Strait is a high possibility source sites for energetic, long-crest, transbasin IWs in the NSCS. The interpretation results of satellite SAR images during a 13 a period from 1995 to 2007 provide the convincing evidence for the conclusions.

Dynamical analysis of mesoscale eddy-induced ocean internal waves using linear theories

This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar （SAR） observations of mesoscale eddies with diameter of several tens of kilometers to hundreds of kilometers show that the internal wave packets with wavelength of hundreds of meters to kilometer exist inside the mesoscale eddies. This coexistence phenomenon and inherent links between the two different scale processes are revealed in the solutions of governing equations and boundary conditions for the internal wave disturbance with a horizontally slowly variable amplitude in a cylindrical coordinate system. The theoretical solutions indicate that the instability of eddy current field provides the dynamical mechanism to internal wave generation. The derived dispersion relation indicates that the internal wave propagation is modified by the eddy current field structure. The energy equation of the internal waves clearly shows the internal wave energy increment comes from the eddy. The theoretical models are used to explain the observation of the mesoscale eddy-induced internal waves off the Norwegian coast. The two-dimensional waveform solution of the anticyclonic eddy-induced internal wave packet appears as ring-shaped curves, which contains the typical features of eddy stream lines. The comparison of theoretical solutions to the structure of the internal wave packets on SAR image shows a good agreement on the major features.

The first quantitative remote sensing of ocean internal waves by Chinese GF-3 SAR satellite

Quantitative analysis and retrieval is given by the State Key Laboratory of Satellite Ocean Environment Dynamics（SOED）,Second Institute of Oceanography（SIO）,State Oceanic Administration（SOA）,China,from the first batch of GF-3 synthetic aperture radar（SAR）data with ocean internal wave features in the Yellow Sea.

Spatial and temporal variation characteristics of ocean waves in the South China Sea during the boreal winter

The spatial and temporal variation characteristics of the waves in the South China Sea （SCS） in the boreal winter during the period of 1979/1980-2011/2012 have been investigated based on the European Centre for Medium-range Weather Forecasts interim （ERA-Interim） reanalysis dataset. The results show that the lead- ing mode of significant wave height anomalies （SWHA） in the SCS exhibits significant interannual variation and a decadal shift around the mid-1990s, and features a basin-wide pattern in the entire SCS with a center located in the west of the Luzon Strait. The decadal change from a weak regime to a strong regime is mainly associated with the enhancement of winter monsoon modulated by the Pacific decadal oscillation （PDO）. The interannual variation of the SWHA has a significant negative correlation with the E1 Nino Southern Oscillation （ENSO） in the same season and the preceding autumn. For a better understanding of the physi- cal mechanism between the SCS ocean waves and ENSO, further investigation is made by analyzing atmo- spheric circulation. The impact of the ENSO on the SWHA over the SCS is bridged by the East Asian winter monsoon and Pacific-East Asian teleconnection in the lower troposphere. During the E1 Nino （La Nino）, the anomalous Philippine Sea anticyclone （cyclone） dominates over the Western North Pacific, helps to weaken （enhance） East Asian winter monsoon and then emerges the negative （positive） SWHA in the SCS.

Effects of winds,tides and storm surges on ocean surface waves in the Sea of Japan

Ocean surface waves are strongly forced by high wind conditions associated with winter storms in the Sea of Japan. They are also modulated by tides and storm surges. The effects of the variability in surface wind forcing, tides and storm surges on the waves are investigated using a wave model, a high-resolution atmospheric mesoscale model and a hydrodynamic ocean circulation model. Five month-long wave model simulations are inducted to examine the sensitivity of ocean waves to various wind forcing fields, tides and storm surges during January 1997. Compared with observed mean wave parameters, results indicate that the high frequency variability in the surface wind filed has very great effect on wave simulation. Tides and storm surges have a significant impact on the waves in nearshores of the Tsushima-kaihyS, but not for other regions in the Sea of Japan. High spatial and temporal resolution and good quality surface wind products will be crucial for the prediction of surface waves in the JES and other marginal seas, especially near the coastal regions.

Instability of Two Interacting Quasi-Monochromatic Waves in Shallow Water

The nonlinear interactions of waves with a double-peaked power spectrum have been studied in shallow water. The starting point is the prototypical equation for nonlinear unidirectional waves in shallow water, i.e. the Korteweg de Vries equation. By means of a multiple-scale technique two defocusing coupled Nonlinear SchrCMinger equations are derived. It is found analytically that plane wave solutions of such a system are unstable for small perturbations, showing that the existence of a new energy exchange mechanism which can influence the behavior of ocean waves in shallow water.

Ocean internal waves interpreted as oscillation travelling waves in consideration of ocean dissipation

Most studies of the synthetic aperture radar remote sensing of ocean internal waves are based on the solitary wave solutions of the Korteweg-de Vries （KdV） equation, and the dissipative term in the KdV equation is not taken into account. However, the dissipative term is very important, both in the synthetic aperture radar images and in ocean models. In this paper, the traveling-wave structure to characterize the ocean internal wave phenomenon is modeled, the results of numerical experiments are advanced, and a theoretical hypothesis of the traveling wave to retrieve the ocean internal wave parameters in the synthetic aperture radar images is introduced.

The mixing mechanism in the formation of ocean shear waves

Based on the quasi-geostrophic vorticity equation, the present peper simulates the water mxing process in the formation Of ocean shear waves using large eddy simulation methods. From Lagrangian tracing, we study the ocean shear wave's changing from wave character to vortex character. The distance between tracer groups increases near the ocean shear wave area, and decreases between ocean shear waves. The tracers that are uniformally distributed in space do not retain the uniform character in the mixing process. The frequency shift of the perturbation waves is caused by their nonlinear interaction. The wave number ratio and phase lag of the initial perturbation waves affect the mixing process, but the results show little difference. The increase of the viscosity coefficient will restrain the mixing process.

Proof of Six-Wave Resonance Conditions of Ocean Surface Gravity Waves in Deep Water

A necessary big step up in the modern water wave theories and their widespread application in ocean engineering is how to obtain 6-wave resonance conditions and to prove it. In the light of the existing forms and characteristics of 3-wave, 4-wave and 5-wave resonance conditions, the 6-wave resonance conditions are proposed and proved for currently a maximum wave-wave resonance interactions of the ocean surface gravity waves in deep water, which will be indispensable to both the Kolmogorov spectrum of the corresponding universal wave turbulence and a synthetic 4-5-6-wave resonant model for the ocean surface gravity waves.

Impact of the Waves on the Sea Surface Roughness under Uniform Wind Conditions:Idealized Cases for Uniform Winds(Part I)

The effect of the surface gravity waves over sea surface roughness length (z0) is investigated from several idealized numerical experiments with the Wave-Watch-III (WW3) model. The WW3 model is combined with a simplified model to estimate z0, CD, u* and U10 as function of the sea state. The impacts related to the presence of the ocean waves over z0 are obtained from conditions of growing (young waves) and mature seas (old waves). The wave spectrum is obtained from WW3 model for each idealized simulation under uniform wind conditions. Uniform wind experiments range from 15 to 45 m/s. The simplified algorithm determines z0, CD, u* and U10 for cases of young waves, old waves and by the Charnock method. The results show that when the ocean is characterized by young waves, both z0 and CD (drag coefficient) increase while U10 is reduced. In Charnock case, the values of z0, CD and U10 have no dependence with the presence of gravity waves. Experiments using winds higher than 30 m/s result in young waves’ CD values higher than the CD value for old waves. Even for young waves CD values are high for cases of strong winds. The results also show that in experiments using winds higher than 30 m/s the dependence between CD and wave age becomes stronger, which is in accordance with other studies.

Nolinear waves and their barotropic stability in the tropical ocean and atmosphere

In this paper, the nonlinear waves and their barotropic stability in the tropical ocean and atmosphere are studied with the qualitative theory of the ordinary differential equation. The relationship is derived between the stability of nonlinear waves with different frequencies and the basic currents and their horizontal shear in the tropical ocean and atmosphere.

Modeling ocean wave propagation under sea ice covers

Operational ocean wave models need to work globally, yet current ocean wave models can only treat ice covered regions crudely. The purpose of this paper is to provide a brief overview of ice effects on wave propagation and different research methodology used in studying these effects. Based on its proximity to land or sea, sea ice can be classified as： landfast ice zone, shear zone, and the marginal ice zone. All ice covers attenuate wave energy. Only long swells can penetrate deep into an ice cover. Being closest to open water, wave propagation in the marginal ice zone is the most complex to model. The physical appearance of sea ice in the marginal ice zone varies. Grease ice, pancake ice, brash ice, floe aggregates, and continuous ice sheet may be found in this zone at different times and locations. These types of ice are formed under different thermalmechanical forcing. There are three classic models that describe wave propagation through an idealized ice cover： mass loading, thin elastic plate, and viscous layer models. From physi cal arguments we may conjecture that mass loading model is suitable for disjoint aggregates of ice floes much smaller than the wavelength, thin elastic plate model is suitable for a con tinuous ice sheet, and the viscous layer model is suitable for grease ice. For different sea ice types we may need different wave ice interaction models. A recently proposed viscoelas tic model is able to synthesize all three classic models into one. Under suitable limiting conditions it converges to the three previous models. The complete theoretical framework for evaluating wave propagation through various ice covers need to be implemented in the operational ocean wave models. In this review, we introduce the sea ice types, previous wave ice interaction models, wave attenuation mechanisms,the methods to calculate wave reflection and transmission between different ice covers, and the effect of ice floe breaking on shaping the sea ice morphology. Laboratory experiments, field measurements and numerical simulations supporting the fundamental research in waveice interaction models are discussed. We conclude with some outlook of future research needs in this field.

Information System for Ocean Wave Resources and Its Application to Wave Power Utilization

An information system for ocean wave resources and its application to wave power utilization are introduced. It can manage, analyze and process the data in the monthly report of ocean wave observation records of the State Ocean Administration, and can provide various kinds of curves and numerical characters of statistics. This system has been put into utility in Guangzhou Institute of Energy Conversion (GIEC), the Chinese Academy of Sciences since 1996. An application example is given of the investigation and analysis on ocean wave resource of the Nan Ao Island, Guangdong Province, where a 100 kW onshore OWC (oscillating water column) wave power station will be built. The wave power distribution is obtained in different wave directions for different wave periods. It is found that 70 percent of the wave power comes from the direction of ENE, and more than 95 percent of the wave power is related with direction E. The average wave power density is about 3 kW/m, and more than 80 percent of the wave power is distributed in the wave periods of 4 second to 5 second. Based on the analysis of wave resources, a site on the east coast of the island and a design width of 20 m for the 100 kW station are suggested.

The Assessment of Ocean Wave Energy Along the Coasts of Taiwan

The wave energy resource around the coasts of Taiwan is investigated with wave buoy data covering a 3-year period （2007-2009）. Eleven study sites within the region bounded by the 21.5^°N-25.5°N latitudes and 118°E-122°E longitudes are selected for analysis. The monthly moving-average filter is used to obtain the low-frequency trend based on the available hourly data. After quantifying the wave power and annual wave energy, the substantial resource is the result of Penghu buoy station, which is at the northeastern side of Penghu Island in the Taiwan Strait. it is investigated that the Penghu sea area is determined to be the optimal place for wave energy production according to its abundant resource of northeasterly monsoon waves, sheltering of the Taiwan Island, operation and maintenance in terms of seasonal conditions, and constructability of wave power devices.

Electromagnetic backscattering from one-dimensional drifting fractal sea surface Ⅰ：Wave–current coupled model

To study the electromagnetic backscattering from a one-dimensional drifting fractal sea surface,a fractal sea surface wave–current model is derived,based on the mechanism of wave–current interactions.The numerical results show the effect of the ocean current on the wave.Wave amplitude decreases,wavelength and kurtosis of wave height increase,spectrum intensity decreases and shifts towards lower frequencies when the current occurs parallel to the direction of the ocean wave.By comparison,wave amplitude increases,wavelength and kurtosis of wave height decrease,spectrum intensity increases and shifts towards higher frequencies if the current is in the opposite direction to the direction of ocean wave.The wave–current interaction effect of the ocean current is much stronger than that of the nonlinear wave–wave interaction.The kurtosis of the nonlinear fractal ocean surface is larger than that of linear fractal ocean surface.The effect of the current on skewness of the probability distribution function is negligible.Therefore,the ocean wave spectrum is notably changed by the surface current and the change should be detectable in the electromagnetic backscattering signal.

Critical State Sedimentation Line of Soft Marine Clays

The compression behavior responsible for unity sensitivity is very valuable in quantitative assessment of the effects of soil structure on the compression behavior of soft marine sediments. However, the quantitative assessment of such effects is not possible because of unavailability of the formula for the compression curve of marine sediments responsible for unit sensitivity. In this study, the relationship between the remolded state and the conventional critical state line is presented in the deviator stress versus mean effective stress plot. The analysis indicates that the remolded state is on the conventional critical state line obtained at a relatively small strain. Thus, a unique critical state sedimentation line for marine sediments of unit sensitivity is proposed. The comparison between the critical state sedimentation line proposed in this study and the existing normalized consolidation curves obtained from conventional oedometer tests on remolded soils or reconstituted soils explains well the

Verification of an operational ocean circulation-surface wave coupled forecasting system for the China＇s seas

An operational ocean circulation-surface wave coupled forecasting system for the seas off China and adjacent areas（OCFS-C） is developed based on parallelized circulation and wave models. It has been in operation since November 1, 2007. In this paper we comprehensively present the simulation and verification of the system, whose distinguishing feature is that the wave-induced mixing is coupled in the circulation model. In particular, with nested technique the resolution in the China＇s seas has been updated to（1/24）° from the global model with（1/2）°resolution. Besides, daily remote sensing sea surface temperature（SST） data have been assimilated into the model to generate a hot restart field for OCFS-C. Moreover, inter-comparisons between forecasting and independent observational data are performed to evaluate the effectiveness of OCFS-C in upper-ocean quantities predictions, including SST, mixed layer depth（MLD） and subsurface temperature. Except in conventional statistical metrics, non-dimensional skill scores（SS） is also used to evaluate forecast skill. Observations from buoys and Argo profiles are used for lead time and real time validations, which give a large SS value（more than 0.90）. Besides, prediction skill for the seasonal variation of SST is confirmed. Comparisons of subsurface temperatures with Argo profiles data indicate that OCFS-C has low skill in predicting subsurface temperatures between 100 m and 150 m. Nevertheless, inter-comparisons of MLD reveal that the MLD from model is shallower than that from Argo profiles by about 12 m, i.e., OCFS-C is successful and steady in MLD predictions. Validation of 1-d, 2-d and 3-d forecasting SST shows that our operational ocean circulation-surface wave coupled forecasting model has reasonable accuracy in the upper ocean.