Wave effects on the retrieved wind field from the advanced scatterometer(ASCAT)

To improve retrieval accuracy, this paper studies wave effects on retrieved wind field from a scatterometer. First, the advanced scatterometer （ASCAT） data and buoy data of the National Data Buoy Center （NDBC） are collocated. Buoy wind speed is converted into neutral wind at 10 m height. Then, ASCAT data are com- pared with the buoy data for the wind speed and direction. Subsequently, the errors between the ASCAT and the buoy wind as a function of each wave parameter are used to analyze the wave effects. Wave param- eters include dominant wave period （dpd）, significant wave height （swh）, average wave period （apd） and the angle between the dominant wave direction （dwd） and the wind direction. Collocated data are divided into sub-datasets according to the different intervals of each wave parameter. A root mean square error （RMSE） for the wind speed and a mean absolute error （MAE） for the wind direction are calculated from the sub-datasets, which are considered as the function of wave parameters. Finally, optimal wave conditions on wind retrieved from the ASCAT are determined based on the error analyses. The results show the ocean wave parameters have correlative relationships with the RMSE of the retrieved wind speed and the MAE of the retrieved wind direction. The optimal wave conditions are presented in terms of dpd, swh, apd and angle.

Elimination of Wind Wave Effects on Sub-Bottom Profiler Record

With the presence of wind waves, the swaying of survey vessel may effect the quality of sub-bottom profiler records and, therefore, it is necessary to correct the distortions induced by wave action. A major issue is to distinguish wind wave effect and real bedforms such as sand waves. In this paper, a bandstop filter is designed according to the frequency features of wind wave effect to treat the distortion of seabed topography by wind waves. The technique is used to correct the sub-bottom profile in order to eliminate the wave-induced distortions for the sub-bottom profile records from the Yangtze Estuary. This study shows that the undulate seabed record is resulted from wave action, rather than the presence of sand waves, and the filtration technique helps to eliminate the wave effect and recover the real morphology of seabed and the sediment sequence underneath. In addition, a method for data processing is proposed for the case that the record indeed represents a combination of wave effects and real bedforms.

Relativistic and distorted wave effects on Xe 4d electron momentum distributions

The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons.The theoretical results show good agreements with the experimental data measured previously with electron momentum spectroscopy. The distorted wave effect and the relativistic effect are found to play important roles in the low and high momentum regions, respectively.

Effects of Irregular Wave Groups on Pile Forces

The wave forces on 1,2 and 4 vertical circular piles under the action of several wave trains of the same wave parameters, such as Hs Tp and Mo, but different wave group factors GF are measured in the laboratory. After comparing these forces, it may be concluded that the mean and significant wave forces are almost of no difference for the wave trains with different GF. When GF is larger, the one-tenth of the wave force extreme is slightly increased and the maximum wave force is much larger than the ones with smaller GF, to which attention must be paid in engineering practice.

Seismogenic ULF/ELF Wave Phenomena: Recent Advances and Future Perspectives

There has been enormous progress in the field of electromagnetic phenomena associated with earthquakes (EQs) and EQ prediction during the last three decades, and it is recently agreed that electromagnetic effects do appear prior to an EQ. A few phenomena are well recognized as being statistically correlated with EQs as promising candidates for short-term EQ predictors: the first is ionospheric perturbation not only in the lower ionosphere as seen by subionospheric VLF (very low frequency, 3 kHz f 30 kHz)/LF (low frequency, 30 kHz f 300 kHz) propagation but also in the upper F region as detected by ionosondes, TEC (total electron content) observations, satellite observations, etc, and the second is DC earth current known as SES (Seismic electric signal). In addition to the above two physical phenomena, this review highlights the following four physical wave phenomena in ULF (ultra low frequency, frequency Hz)/ELF (extremely low frequency, 3 Hz frequency 3 kHz) ranges, including 1) ULF lithospheric radiation (i.e., direct radiation from the lithosphere), 2) ULF magnetic field depression effect (as an indicator of lower ionospheric perturbation), 3) ULF/ELF electromagnetic radiation (radiation in the atmosphere), and 4) Schumann resonance (SR) anomalies (as an indicator of the perturbations in the lower ionosphere and stratosphere). For each physical item, we will repeat the essential points and also discuss recent advances and future perspectives. For the purpose of future real EQ prediction practice, we pay attention to the statistical correlation of each phenomenon with EQs, and its predictability in terms of probability gain. Of course, all of those effects are recommended as plausible candidates for short-term EQ prediction, and they can be physically explained in terms of the unified concept of the lithosphere-atmosphere-ionosphere coupling (LAIC) process, so a brief description of this coupling has been carried out by using these four physical parameters though the mechanism of each phenomenon is still poorly understood. In conclusion, we have to emphasize the importance of more statistical studies for more abundant datasets sometimes with the use of AI (artificial intelligence) techniques, more case studies for huge (M greater than 7) EQ events, recommendation of critical analyses, and finally multi-parameters observation (even though it is tough work).

Effects of Breaking Waves on Composite Backscattering from Ship-Ocean Scene

The existence of the sea surface is bound to affect the electromagnetic （EM） scattering from marine targets. When dealing with the composite scattering from targets over a sea surface by applying high-frequency EM theories, the total scattering field can be decomposed into three parts in low sea states, namely, the direct scattering from the sea surface, the direct scattering from targets and the coupling scattering between the sea surface and targets. With regard to high sea states, breaking waves make the direct scattering from the sea surface and the coupling scattering more complicated. To solve this issue, a scattering model is proposed to analyze the composite scattering from a ship over a rough sea surface under high sea states. To consider the effect of breaking waves, a three dimensional geometric model is adopted together with Ufimtsev＇s theory of edge waves for the scattering from a breaker. In addition, the coupling scattering between targets and breaking waves is taken into account by considering all possible scattering paths. The simulated results indicate that the influence of breaking waves on the scattering field from the sea surface and on the coupling field is non-negligible, and the numerical results also show the effectiveness of the proposed scattering model.

Some Effects of Rotation Rate on Planetary-Scale Wave Flows

A series of experiments were performed in a rotating annulus of fluid to study effects of rotation rate on pianeta ry-scale baroclinic wave flows. The experiments reveal that change in rotation rate of fluid container causes variation in Rossby number and Taylor number in flows and leads to change in flow patterns and in phase and amplitude of quasi-stationary waves. For instance, with increasing rotation rate, amplitude of quasi-stationary waves increases and phase shifts upstream. On the contrary, with decreasing rotation rate, amplitude of quasi-stationary waves de creases and phase shifts downstream. In the case of the earth's atmosphere, although magnitude of variation in earth's rotation rate is very small, yet it causes a very big change in zonal velocity component of wind in the atmosphere and of currents in the ocean, and therefore causes a remarkable change in Rossby number and Taylor number determining regimes in planetary-scale geophysical flows. 1 he observation reveals that intensity and geographic location of subtropic anticyclones in both of the Northern and Southern Hemispheres change consistently with the variation in earth's rotation rate. The results of fluid experiments are consistent, qualitatively, with observed phenomena in the atmospheric circulation.

The Effects of Zonal Flow on Nonlinear Rossby Waves

In this paper, we using phase plane method have derived the stability criteria of linear and nonlinear Rossby waves under the conditions of semi-geostrophic approximation and have gotten the solutions and geostrophic vorticity of corresponding solitary Rossby waves. It is pointed out that the wave stability is connected with the distribution of zonal flow and when the zonal flow is different the solitary wave trough or ridge is formed.

EFFECTS OF BOTTOM TOPOGRAPHY ON THE STANDING WAVES IN CIRCULAR BASINS

Standing waves in the cylinder hasins with inhomogeneous bottom are considered in this paper. We assume that the inviscid, incompressible fluid is in irrotational undulatory motion. For convenience sake, cylindrical coordinates are chosen. The velocitv potentials, the wave profiles and the modified frequencies are determined (to the third order) as power series in terms of the amplitude divided by the wavelength. Axisymmetrical analytical solutions are worked out. When w=0 , the second order frequency are gained.As an example, we assume that cylinder bottom is an axisymmetricat paraboloid. We find out that the uneven bottom has influences on standing waves. In the end. we go into detail on geometric factors.

Wave Breaking Phenomena of Irregular Waves Combined with Opposing Current

Experimental study and theoretical analysis show that the critical value of relative wave height (H / d)b given by Goda and the critical wave steepness (H / L)b given by Michell and Miche can be adopted as the spilling breaking indices of regular waves. According to the same principle, a systematic theoretical analysis and experiment of irregular wave have been done by the authors in order to solve the breaking problem of irregular waves. It is indicated that the authors' method for determining wave breaking of regular waves can also be used for irregular waves.

INVESTIGATION AND APPLICATION OF LAWS OF TWO DIMENSIONAL TRANSFORMATION OF SANDY BEACHES UNDER WAVE ACTION

Based on previous research results and experimental studies, this paper indicates the important factors affecting two-dimensional transformation of sandy beaches, especially the characteristic slope and sediment transport factor. A discrimination criterion of transformation type of sandy beaches is derived by applying the theory of wave energy dissipation rate. This criterion is closely examined with a lot of data and can be used to forecast the transformation of sandy beaches under the action of varying wave climates.

UNIFIED EQUIVALENT HARMONIC LOADING ON SEABED FOUNDATIONS UNDER RANDOM WAVE LOADING

In accordance with laboratory tests and theoretical analysis, the concept of unified equivalent harmonic wave loading is suggested and discussed in this paper. Such a concept may be more reasonable and widely applicable in offshore foundation engineering. A verification test has also been completed, in which the random wave loading and the corresponding unified equivalent loading were applied on soil samples. The test results show that the equivalent effect is satisfactory.

NUMERICAL CALCULATION OF HYDRODYNAMIC COEFFICIENT FOR A FLOATING BODY IN WAVES

A preliminary numerical model of the buoyant drum by wave action is presented, which is based on the Finite Boundary Element Method of the source distribution. A series formula of Green's function is used for the derivation of the model. In the paper the calculated results of the examples for a sphere and a buoyant drum are close to the data in some references. A subject of great interest to ocean engineers is the response a floating body suffers in ocean waves. In this paper, the oscillatory motion of a buoyant drum is analysed and a calculating method is presented. Applying this calculating method, the hydrodynamic coefficient for any kind of floating bodies can be obtained.

TRANSVERSE FORCES ON VERTICAL PILE IN REGULAR AND IRREGULAR WAVES

The magnitude and the fluctuating frequency of the total transverse wave forces, particularly those by irregular waves on an isolated pile are investigated experimentally. The results indicate that the transverse force (FL) is usually not negligible and the resultant force (FR) of the transverse force and the inline force may be 40% (in regular waves) or 18% (in irregular waves) larger than the inline force (F). The plots of FL/F, FR/F and several kinds of lift coefficient CL versus KC number are given for both regular waves and irregular waves. The methods for estimating the total transverse forces and resultant wave forces are suggested.

Hydrodynamic Forces on Inclined Cylinder due to Waves with Crossing Current

Based on Morison's Equation and linear wave theory, hydrodynamic forces acting on inclined cylinders due to waves and crossing current at an angle of αs are analyzed. A method for calculating exciting forces is proposed. Experimental results show that the proposed method in this paper is feasible and can be used in engineering practice.

MULTI-DIRECTIONAL WAVE SUPERPOSITION OF WAVE DIFFRACTION

Characteristics of a natural wave cannot be successfully described by only using wave frequency spectra. In the laboratory, natural wave conditions cannot be simulated exactly by a harbor sheltering experiment with irregular long-crested waves, especially since the results of diffraction tests with reflection source are often inaccurate. Only a small number of laboratories in the world have possessed a directional spectrum wave producer because of its complication and expension. This paper describes the experiment for multi-directional wave superposition of wave diffraction, with the conventional regular wave producer and one-direction irregular wave producer. The test results are of equal value with that from a directional spectra wave. This method is suitable for rational design of harbor engineering projects and can be adopted in future practice.

Traveling wave effect on the seismic response of a steel arch bridge subjected to near fault ground motions

In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined, with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave （only time delay considered） effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also discussed.

An assessment of global ocean wave energy resources over the last 45 a

Against the background of the current world facing an energy crisis,and human beings puzzled by the problems of environment and resources,developing clean energy sources becomes the inevitable choice to deal with a climate change and an energy shortage.A global ocean wave energy resource was reanalyzed by using ERA-40 wave reanalysis data 1957–2002 from European Centre for Medium-Range Weather Forecasts（ECMWF）.An effective significant wave height is defined in the development of wave energy resources（short as effective SWH）,and the total potential of wave energy is exploratively calculated.Synthetically considering a wave energy density,a wave energy level probability,the frequency of the effective SWH,the stability and long-term trend of wave energy density,a swell index and a wave energy storage,global ocean wave energy resources were reanalyzed and regionalized,providing reference to the development of wave energy resources such as wave power plant location,seawater desalination,heating,pumping.

Study on Wave Dissipation of the Structure Combined by Baffle and Submerged Breakwater

This paper proposes a structure combined by baffle and submerged breakwater （abbreviated to SCBSB in the following texts）. Such a combined structure is conducive to the water exchange in the harbor, and has strong capability on wave dissipation. Our paper focuses on the discussion of two typical structures, i.e., the submerged baffle and rectangular breakwater combined with the upper baffle respectively, which are named as SCBSB 1 and SCBSB2 for short. The eigenfunction method corrected by experimental results is used to investigate the wave dissipation characteristics. It shows that the calculated results agree well with the experimental data and the minimum value of the wave transmission coefficient can be obtained when the distance between the front and rear structures is from 1/4 to 1/2 of the incident wave length.

AERODYNAMIC FORCES ACTING ON AN ALBATROSS FLYING ABOVE SEA-WAVES

Numerical investigation on the dynamic mechanism has been made for an albatross to fly effectively near sea surface. Emphasizing on the effect of the sea wave, the albatross is simplified as a two-dimensional airfoil and the panel method based on the potential flow theory is employed to calculate the wave effect on the aerodynamic forces. The numerical results have been presented for the states of flying at different constant speeds with constant heights above sea level, and flying at different constant speeds with the combined oscillations of pitching and free heaving. It is shown that the albatross flight efficiency depends on not only the speed and height of flight but also the wave amplitude and the wavelength. The albatross benefits by wave effect to get thrust, so as to reduce the resistance in the circumstances of rough sea.