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基于北京遥测技术研究所机载波谱仪实测数据以及ECMWF提供的风场数据,分析了不同风速条件下小入射角海浪平均后向散射系数不对称性与各向异性随入射角的变化特性,并对导致这一现象的原因进行了初步分析。结果表明:小入射角下,海浪平均后向散射系数随入射角增大呈现递减趋势并在18°时达到某一稳定值,之后基本维持不变;海浪后向散射系数不对称性与各向异性均随入射角增大呈现递增趋势,同样在18°增大至某一稳定值,之后基本维持不变;低风速条件下,海浪不对称性和各向异性与风速有关,且风速越大不对称性与各向异性越明显。 相似文献
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A new method for estimating significant wave height(SWH) from advanced synthetic aperture radar(ASAR) wave mode data based on a support vector machine(SVM) regression model is presented. The model is established based on a nonlinear relationship between σ0, the variance of the normalized SAR image, SAR image spectrum spectral decomposition parameters and ocean wave SWH. The feature parameters of the SAR images are the input parameters of the SVM regression model, and the SWH provided by the European Centre for Medium-range Weather Forecasts(ECMWF) is the output parameter. On the basis of ASAR matching data set, a particle swarm optimization(PSO) algorithm is used to optimize the input kernel parameters of the SVM regression model and to establish the SVM model. The SWH estimation results yielded by this model are compared with the ECMWF reanalysis data and the buoy data. The RMSE values of the SWH are 0.34 and 0.48 m, and the correlation coefficient is 0.94 and 0.81, respectively. The results show that the SVM regression model is an effective method for estimating the SWH from the SAR data. The advantage of this model is that SAR data may serve as an independent data source for retrieving the SWH, which can avoid the complicated solution process associated with wave spectra. 相似文献
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针对斑点噪声降低机载波谱仪海浪谱反演精度问题,基于STORM机载波谱仪VALPARESO试验数据,分别使用数学法、阈值法、交叉谱法和小波分析法四种斑点噪声去除方法对其进行去噪处理,得到了去噪前后调制密度谱、海浪谱和噪声谱,并将反演所得海浪谱有效波高与同步观测的浮标结果进行了对比,最后对四种方法的去噪效果以及噪声谱特性进行了分析与评价。结果表明:四种去噪方法均可以有效去除斑点噪声,按照反演精度排序依次为交叉谱法、阈值法、小波分析法和数学法,其中交叉谱方法去噪效果最理想,RMSE仅为0.008,有效波高绝对误差为0.25m,相对误差为7%。 相似文献
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The main objective of this paper is to propose a newly developed ocean Significant Wave Height(SWH) retrieval method from Envisat Advanced Synthetic Aperture Radar(ASAR) imagery. A series of wave mode imagery from January, April and May of 2011 are collocated with ERA-Interim reanalysis SWH data. Based on the matched datasets, a simplified empirical relationship between 22 types of SAR imagery parameters and SWH products is developed with the Genetic Algorithms Partial Least-Squares(GA-PLS) model. Two major features of the backscattering coefficient σ_0 and the frequency parameter S_(10) are chosen as the optimal training feature subset of SWH retrieval by using cross validation. In addition, we also present a comparison of the retrieval results of the simplified empirical relationship with the collocated ERA-Interim data. The results show that the assessment index of the correlation coefficient, the bias, the root-mean-square error of cross validation(RMSECV) and the scattering index(SI) are 0.78, 0.07 m, 0.76 m and 0.5, respectively. In addition, the comparison of the retrieved SWH data between our simplifying model and the Jason-2 radar altimeter data is proposed in our study.Moreover, we also make a comparison of the retrieval of SWH data between our developed model and the wellknown CWAVE_ENV model. The results show that satisfying retrieval results are acquired in the low-moderate sea state, but major bias appears in the high sea state, especially for SWH5 m. 相似文献
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基于2003年5月至10月ENVISAT ASAR宽幅模式（Wide Swath Mode, WSM）数据和2003年11月至2004年5月ENVISAT ASAR单视复数模式（Image Mode SLC, IMS）数据,利用多普勒质心偏移法获取了海面运动引起的多普勒质心异常,通过去除风和Bragg波引起的多普勒频移,最终获得龙目海峡海表径向流速。利用AVISO（Archiving, Validation and Interpretation of Satellite Oceanographic Data）流场数据对结果进行了精度验证,并分析了龙目海峡海表流速变化。结果表明：本文反演得到的海表面流速与AVISO流场匹配度较好,其中由WSM数据反演得到的流速与AVISO流场均方根误差为0.28 m/s,IMS数据反演得到的流速与AVISO流速均方根误差为0.37 m/s。在研究区范围内,2003年5月至9月海流流速较大（-2.56～2.51 m/s）,10月流速减小（-0.79～0.72 m/s）,11月至12月流速逐月增大（-1.64～1.25 m/s）,2004年3月流速达到最低值（-0.58 m/s）,2004年4月至5月流速逐月增大（-1.46～1.72 m/s）;在南半球夏季（12月）和秋季（5月）龙目海峡出现北向逆流,其余皆为南向流。该流场反演方法可有效提取海面流速信息,从而为海面流场变化研究提供有效支撑。 相似文献
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基于浮标和步进频率微波辐射计(SFMR,Stepped-Frequency Microwave Radiometer)数据对NASA JPL(Jet Propulsion Laboratory)和RSS(Remote Sensing Systems)公司分别发布的已广泛应用于全球海面风场观测的ASCAT(Advanced SCATterometer)散射计风产品进行了比较和分析。结果表明,两者风速在中低风速(15 m/s)时基本一致;高风速(15 m/s)时RSS风速整体高于JPL风速。通过浮标数据对比,风速15 m/s时两者风速精度一致;风速15 m/s时两者风速RMS相当,但JPL和RSS风速分别低估和高估。利用SFMR数据检验表明RSS风速与SFMR风速一致性更好。两者风向精度在低风速(5 m/s)时较低,但随风速增加而提高并趋于稳定。该研究结果对相关科研人员的ASCAT散射计风产品选择具有重要的指导意义。 相似文献
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A new algorithm for sea-surface wind-speed retrieval based on the L-band radiometer onboard Aquarius 总被引：1，自引：0，他引：1
Aquarius is the second satellite mission to focus on the remote sensing of sea-surface salinity from space and it has mapped global sea-surface salinity for nearly 3 years since its launch in 2011. However,benefiting from the high atmospheric transparency and moderate sensitivity to wind speed of the L-band brightness temperature(TB),the Aquarius L-band radiometer can actually provide a new technique for the remote sensing of wind speed. In this article,the sea-surface wind speeds derived from TBs measured by Aquarius' L-band radiometer are presented,the algorithm for which is developed and validated using multisource wind speed data,including Wind Sat microwave radiometer and National Data Buoy Center buoy data,and the Hurricane Research Division of the Atlantic Oceanographic and Meteorological Laboratory wind field product. The error analysis indicates that the performance of retrieval algorithm is good. The RMSE of the Aquarius wind-speed algorithm is about 1 and 1.5 m/s for global oceans and areas of tropical hurricanes,respectively. Consequently,the applicability of using the Aquarius L-band radiometer as a near all-weather wind-speed measuring method is verified. 相似文献
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基于Sentinel-3载荷OLCI和SRAL数据的内波同步探测研究 总被引：1，自引：1，他引：0
The ocean and land color instrument(OLCI) and synthetic aperture radar altimeter(SRAL) installed aboard the Sentinel-3 satellite have been in orbit for operational uses. In this study, data collected from Sentinel-3 are used to investigate internal waves in the South China Sea. An internal wave is detected using an OLCI image with a resolution of 300 m, and an analysis was performed with a quasi-synchronous moderate-resolution imaging spectroradiometer(MODIS) image. The opposite characteristics of OLCI and MODIS images of the same internal wave are explained by the critical angle in brightness reversals. The unique observational geometry of the OLCI image and its influence on observations of internal waves are discussed. The distribution of σ0 and sea surface height anomalies(SSHAs) induced by internal waves are studied using SRAL records. The σ0 records of SRAL occasionally show less sensitivity to the modulation of internal waves, which may be attributed to the observational geometry, while SSHAs show obvious variations. The synchronous pairing of OLCI images and SRAL records are analyzed to extract the three-dimensional sea surface signatures induced by internal waves. The analysis demonstrates that the profile of SSHAs in the surface shows an opposite phase to the profiles of internal waves in the ocean. The opposite phase relationship, observed in the remote sensing view, is also confirmed with a laboratory experiment. 相似文献