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1.
Parameterized first-guess spectrum method for retrieving directional spectrum of swell-dominated waves and huge waves from SAR images 总被引：3，自引：0，他引：3
A method to retrieve ocean wave spectra from SAR images, named Parameterized First-guess Spectrum Method (PFSM), was proposed after interpretation of the theory to ocean wave imaging and analysis of the drawbacks of the retrieving model generally used. In this method, with additional information and satellite parameters, the separating wave-number is first calculated to determine the maximum wave-number beyond which the linear relation can be used. The separating wave-number can be calculated using the additional information on wind velocity and parameters of SAR satellite. And then the SAR spectrum can be divided into SAR spectrum of wind wave and of swell according to the result of separating wave-number. The portion of SAR spectrum generated by wind wave, is used to search for the most suitable parameters of ocean wind wave spectrum, including propagation direction of ocean wave, phase speed of dominating wave and the angle spreading coefficient. The swell spectrum is acquired by directly inversing the linear relation of ocean wave spectrum to SAR spectrum given the portion of SAR spectrum generated by swell. We used the proposed method to retrieve the ocean wave spectrum from ERS-SAR data from the South China Sea and compared the result with altimeter data. The agreement indicates that the PFSM is reliable. 相似文献
2.
This paper proposes a joint method to simultaneously retrieve wave spectra at dif ferent scales from spaceborne Synthetic Aperture Radar(SAR) and wave spectrometer data. The method combines the output from the two dif ferent sensors to overcome retrieval limitations that occur in some sea states. The wave spectrometer sensitivity coeffi cient is estimated using an ef fective signifi cant wave height(SWH), which is an average of SAR-derived and wave spectrometer-derived SWH. This averaging extends the area of the sea surface sampled by the nadir beam of the wave spectrometer to improve the accuracy of the estimated sensitivity coeffi cient in inhomogeneous sea states. Wave spectra are then retrieved from SAR data using wave spectrometer-derived spectra as fi rst guess spectra to complement the short waves lost in SAR data retrieval. In addition, the problem of 180° ambiguity in retrieved spectra is overcome using SAR imaginary cross spectra. Simulated data were used to validate the joint method. The simulations demonstrated that retrieved wave parameters, including SWH, peak wave length(PWL), and peak wave direction(PWD), agree well with reference parameters. Collocated data from ENVISAT advanced SAR(ASAR), the airborne wave spectrometer STORM, the PHAROS buoy, and the European Centre for Medium-Range Weather Forecasting(ECMWF) were then used to verify the proposed method. Wave parameters retrieved from STORM and two ASAR images were compared to buoy and ECMWF wave data. Most of the retrieved parameters were comparable to reference parameters. The results of this study show that the proposed joint retrieval method could be a valuable complement to traditional methods used to retrieve directional ocean wave spectra, particularly in inhomogeneous sea states. 相似文献
3.
Observation and analysis of ocean wave diffraction in near-shore and near-island region was performed with Synthetic Aperture Radar (SAR) data, using an optimized retrieval method named parameterized first-guess spectrum retrieval method. The results retrieved from ERS-SAR and ENVISAT-ASAR images showed that, in the region sheltered by land jut, the energy of long waves is reduced by 10%-20% and that the propagation direction of long waves is changed due to the effect of topography. In the shadow zone behind the island, ocean wave can propagate along the seashore instead of perpendicular to the coastline, as shown by SAR images. 相似文献
4.
针对现有GPS海浪测量技术的不足,提出基于TRACK的GPS海浪测量方法,即利用TRACK解得海上载体高精度的垂向位移,经浪潮分离提取海浪信号,采用周期图法估计海浪信号的功率谱,计算海浪要素。利用实测数据进行实验,结果表明,平均波高和平均周期与测波仪结果差异分别小于2 cm和0.25 s,验证了本文方法的有效性。 相似文献
5.
Depth inversion in coastal water based on SAR image of waves 总被引：1，自引：0，他引：1
Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar （SAR） image of waves. Based on the general dispersion relation of ocean waves the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths. 相似文献
6.
The objective of this paper is to propose an empirical method to inverse significant wave height(SWH)under typhoon conditions from collected dual-polarization Gaofen(GF)-3 synthetic aperture radar(SAR)imagery.The typhoon scenes were cap-tured from narrow scan(NSC)and wide scan(WSC)images,and collocated with European Center for Medium-Range Weather Fore-casts reanalysis data of(ECMWF).To improve the quality of GF-3 SAR images,the recalibration over rainforest and de-scalloping were carried out.To establish the empirical relationship between SAR-derived parameters and collocated SWH,the sensitivity analysis of typical parameters about the normalized radar cross section(Nrcs)and imagery variance(Cvar)were performed to both VV and VH polarized images.Four scenes from GF-3 SAR imagery under typhoon conditions were used for training the model by the multivari-ate least square regression,and one scene was used for preliminary validation.It was found that the joint retrieval model based on VV and VH polarized SAR imagery performed better than any single polarized model.These results,verified by using ECMWF data,revealed the soundness of this approach,with a correlation of 0.95,bias of 0 m,RMSE of 0.44 and SI of 0.01 when VV polarization and VH polarization data were both used. 相似文献
7.
Under suitable conditions of tidal current and wind, underwater topography can be detected by synthetic aperture radar (SAR)
indirectly. Underwater topography SAR imaging includes three physical processes: radar ocean surface backscattering, the modulation
of sea surface short wave spectrum by the variations in sea surface currents, and the modulation of sea surface currents by
the underwater topography. The first process is described usually by Bragg scattering theory because the incident angle of
SAR is always between 20°–70°. The second process is described by the action balance equation. The third process is described
by an ocean hydrodynamic model. Based on the SAR imaging mechanism for underwater topography, an underwater topography SAR
detection model and a simplified method for its calculation are introduced. In the detection model, a two-dimensional hydrodynamic
model — the shallow water model is used to describe the motion of tidal current. Due to the difficulty of determining the
expression of SAR backscattering cross section in which some terms can not be determined, the backscattering cross section
of SAR image used in the underwater topography SAR detection is pro-processed by the simulated SAR image of the coarse-grid
water depth to simplify the calculation. Taiwan Shoal, located at the southwest outlet of Taiwan Strait, is selected as an
evaluation area for this technique due to the occurrence of hundreds of sand waves. The underwater topography of Taiwan Shoal
was detected by two scenes of ERS-2 SAR images which were acquired on 9 January 2000 and 6 June 2004. The detection results
are compared with in situ measured water depths for three profiles. The average absolute and relative errors of the best detection
result are 2.23 m and 7.5 %, respectively. These show that the detection model and the simplified method introduced in the
paper is feasible. 相似文献
8.
YANG Ying-hui CHEN Qiang LIU Guo-xiang Li Zhi-lin CHENG Hai-qin Liu Li-yao 《山地科学学报》2013,10(5):790-800
In order to overcome the limitation of cross correlation coregistration method for Synthetic Aperture Radar(SAR) interferometric pairs with low coherence,a new image coregistration algorithm based on Fringe Definition Detection(FDD) is presented in this paper.The Fourier transformation was utilized to obtain spectrum characteristics of interferometric fringes.The ratio between spectrum mean and peak was proposed as the evaluation index for identifying homologous pixels from interferometric images.The satellites ERS-1/2 C-band SAR acquisitions covering the Yangtze River plain delta,eastern China and ALOS/PALSAR L-band images over the Longmen Shan mountainous area,southwestern China were respectively employed in the experiment to validate the proposed coregistration method.The testing results suggested that the derived Digital Elevation Model(DEM) from FDD method had good agreement with that from the cross correlation method as well as the reference DEM at high coherence area.However,The FDD method achieved a totally improved topographic mapping accuracy by 24 percent in comparison to the cross correlation method.The FDD method also showed better robustness and achieved relatively higher performance for SAR image coregistration in mountainous areas with low coherence. 相似文献
9.
Significant wave height is an important criterion in designing coastal and offshore structures. Based on the orthogonality
principle, the linear mean square estimation method is applied to calculate significant wave height in this paper. Twenty-eight-year
time series of wave data collected from three ocean buoys near San Francisco along the California coast are analyzed. It is
proved theoretically that the computation error will be reduced by using as many measured data as possible for the calculation
of significant wave height. Measured significant wave height at one buoy location is compared with the calculated value based
on the data from two other adjacent buoys. The results indicate that the linear mean square estimation method can be well
applied to the calculation and prediction of significant wave height in coastal regions. 相似文献
10.
When exploring the temporal and spatial change law of ocean environment, the most common method used is using smaller-scale observed data to derive the change law for a larger-scale system. For instance, using 30-year observation data to derive 100-year return period design wave height. Therefore,the study of inherent self-similarity in ocean hydrological elements becomes increasingly important to the study of multi-year return period design wave height derivation. In this paper, we introduced multifractal to analyze the statistical characteristics of wave height series data observed from oceanic hydrological station.An improvement is made to address the existing problems of the multifractal detrended fluctuation analysis(MF-DFA) method, where trend function showed a discontinuity between intervals. The improved MFDFA method is based on signal mode decomposition, replacing piecewise polynomial fitting used in the original method. We applied the proposed method to the wave height data collected at Chaolian Island,Shandong, China, from 1963 to 1989 and was able to conclude the wave height sequence presented weak multi-fractality. This result provided strong support to the past research on the derivation of multi-year return period design wave height with observed data. Moreover, the new method proposed in this paper also provides a new perspective to explore the intrinsic characteristic of data. 相似文献
11.
Hongyuan Shi Xuefeng Cao Xianhua Wen Maochong Shi Dongliang Zhao Peifang Guo 《中国海洋大学学报(英文版)》2017,16(1):8-14
Based upon the one-year wind wave measurement data, collected from the South China Sea (SCS) at coordinates 20° 36.298′N, 110°45.433′E. by Acoustic Wave And Current (AWAC), we analyzed the wave characteristics and concluded that the most common wave direction was E and the second most common direction was ENE, the mean and the maximum values of significant height was 1.2 m and 4.36 m, respectively. The mean period was 4.0 s. We also evaluated the wave spectrums under conditions existing in three typhoons: Rumbi, Jeti and Utor. We found that unimodal spectrums occurred more often than others, and the maximum spectrum peak was 30.7911 m2 s. The minimum peak frequency was 0.0625 Hz, and the mean peak frequency was 0.126 Hz. The wave period is important for the design of marine structures, especially the position of peak frequency had a great influence on the stress calculation. Spectral analysis showed that the values of peak frequency distributed between 0.063 Hz and 0.217 Hz, with the mean value 0.114 Hz. We fit the normalized spectrum with 6 theoretical spectral models, out of which, the Wen spectrum, JONSWAP spectrum and Wallops spectrum were proved to give the best fit. What distinguished the Wen Spectrum from the rest was that it does not rely on the measured spectrum for parameter estimation. Hence, we recommend that the Wen spectrum should be widely used in marine construction. 相似文献
12.
根据某大坝右岸围堰爆破，对爆破地震波三维空间的频谱、加速度、速度、动力放大倍数进行了研究，得到爆破地震波在砼重力坝的不同高度、不同方向、不同介质中的反应特性。 相似文献
13.
lareODUcrI0NThephenomenonofbreakingwavesintheoasnoocurswheneveramomentahiyhighcrestmecheSanunstablecondition.It0ccursintendtimhy,andtheoccurrencefre-qUencydePendsonthescastate.ManystudAshaddricaniedoutontheoccurmcefre-qUencyofbrmkingwavesindeepweter.0chiandTsai(l983),LongueHiggins(l975)andVanD0mandPamn(l975)nadstheptalictonofbrmkingwavesoccurrenceindeePwater,usingabaskingcriterionforindividualwavesbasedonthewavesmpness.ThecriterioncanbeexpmeedintennSofthewaVehdghtHandperiodTasH>PgT'(… 相似文献
14.
The inflow angle of tropical cyclones(TC) is generally neglected in numerical studies of ocean surface waves induced by TC.In this study,the impacts of TC inflow angle on ocean surface waves were investigated using a high-resolution wave model.Six numerical experiments were conducted to examine,in detail,the effects of inflow angle on mean wave parameters and the spectrum of wave directions.A comparison of the waves simulated in these experiments shows that inflow angle significantly modifies TC-induced ocean surface waves.As the inflow angle increases,the asymmetric axis of the significant wave height(SWH) field shifts 30u clockwise,and the maximum SWH moves from the front-right to the rear-right quadrant.Inflow angle also affects other mean wave parameters,especially in the rear-left quadrant,such as the mean wave direction,the mean wavelength,and the peak direction.Inflow angle is a key factor in wave models for the reproduction of double-peak or multi-peak patterns in the spectrum of wave directions.Sensitivity experiments also show that the simulation with a 40u inflow angle is the closest to that of the NOAA statistical SLOSH inflow angle.This suggests that 40u can be used as the inflow angle in future TC-induced ocean surface wave simulations when SLOSH or observed inflow angles are not available. 相似文献
15.
《中国海洋湖沼学报》2019,(6)
Offshore waters provide resources for human beings, while on the other hand, threaten them because of marine disasters. Ocean stations are part of offshore observation networks, and the quality of their data is of great significance for exploiting and protecting the ocean. We used hourly mean wave height, temperature, and pressure real-time observation data taken in the Xiaomaidao station(in Qingdao, China) from June 1, 2017, to May 31, 2018, to explore the data quality using eight quality control methods, and to discriminate the most effective method for Xiaomaidao station. After using the eight quality control methods, the percentages of the mean wave height, temperature, and pressure data that passed the tests were 89.6%, 88.3%, and 98.6%, respectively. With the marine disaster(wave alarm report) data, the values failed in the test mainly due to the influence of aging observation equipment and missing data transmissions. The mean wave height is often affected by dynamic marine disasters, so the continuity test method is not effective. The correlation test with other related parameters would be more useful for the mean wave height. 相似文献
17.
水库滑坡约束条件影响其运动过程的几何形态, 是滑坡涌浪预测的重要参数之一。为了探究约束条件对滑坡涌浪特征(波高、波幅与周期)的影响, 采用正交试验设计法开展了54组滑坡涌浪室内模型试验, 并基于统计学理论对约束散体和半约束散体的涌浪特征进行了分析。结果表明: 涌浪波周期基本不受滑体约束条件的影响; 而半约束散体模型的波高和波幅小于约束散体的波高和波幅, 半约束散体的初始涌浪波高约为约束散体的0.95倍, 半约束散体模型的最大波峰波幅约为约束散体模型的0.9倍。因此, 在开展滑坡涌浪快速预测时, 虽然滑体入水形态与破坏前形态差异巨大, 但基于滑坡初始几何形态参数对其初始涌浪波高和最大涌浪波幅的预测结果是偏安全的。研究结论可以为更准确地预测水库滑坡涌浪提供理论依据。 相似文献
18.
针对近岸区域,基于Sentinel-3A合成孔径雷达观测数据,选取多阈值、ICE1、IceSheet和SAMOSA四种波形重跟踪算法,利用全球范围内27个验潮站海面高数据,分析近岸20 km范围内4种波形重跟踪算法的精度。结果表明,多阈值算法在近岸6 km范围内可保留最多的有效波形,且与验潮站海面高数据具有最高的相关性和最小的均方根误差;SAMOSA算法在离岸距离大于5 km时相对大地水准面稳定性最高,更适用于开阔海域。 相似文献
19.
Ocean internal waves appear as irregular bright and dark stripes on synthetic aperture radar(SAR) remote sensing images. Ocean internal waves detection in SAR images consequently constituted a difficult and popular research topic. In this paper, ocean internal waves are detected in SAR images by employing the faster regions with convolutional neural network features(Faster R-CNN) framework; for this purpose, 888 internal wave samples are utilized to train the convolutional network and identify internal waves. The experimental results demonstrate a 94.78% recognition rate for internal waves, and the average detection speed is 0.22 s/image. In addition, the detection results of internal wave samples under dif ferent conditions are analyzed. This paper lays a foundation for detecting ocean internal waves using convolutional neural networks. 相似文献
20.
大型人工线状地物是人类改造自然的产物,同人类生活息息相关。本文从大型人工线状地物定义出发,阐述了其形变现象、成因及衍生灾害;并利用多基线差分雷达干涉测量技术(DifferentialSyntheticApertureRadarInterferometry,DInSAR)实施大型人工线状地物形变监测。通过多数据源实验(ENVISATASAR,广州;PALSAR,香港大屿山;TerraSAR-X,深圳),分析了当前高级DInSAR方法,包括永久散射体和相干目标法在监测大型人工线状地物形变上的能力。实验结果表明,采用了不同的影像干涉对组合策略,永久散射体法适合大数据量SAR影像处理,而相干目标法适合小数据量SAR影像分析。微波穿透性和垂直临界基线随波长增加而增加。因此,在波段选择上,低相干区宜选用长波SAR数据(比如ALOSPALSAR)以获取稳健反演结果;而高相干区宜选用短波TerraSAR-X或者ENVISATASAR数据,以获取高精度地表形变场。结合线状地物几何和物理特性,分别从先验基础GIS/GPS数据、SAR数据源选择、PS点提取和模型改进四方面进行分析和探讨,认为面向线状地物形变监测多基线DInSAR模型的研发是亟待解决的问题。 相似文献