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太阳耀光是来自粗糙海面的直接太阳反射光,其强度与海面粗糙度密切相关,而海面粗糙度主要受海面风场影响。因此,包含太阳耀光信息的光学遥感影像在海洋动力过程和海面风速探测中具有积极意义。本文利用2016年2月到2017年3月期间成像的25幅Terra卫星MISR(Multi-angle Imaging Spectro Radiometer)传感器的多角度遥感影像,分别提取了太阳的高度角和方位角、正视和后视影像的卫星观测角、方位角等信息,校正获得正视和后视影像的太阳耀光辐射强度,进一步反演海表面粗糙度信息,进而计算海面风速。最后利用ECMWF(European Centre for Medium-Range Weather Forecasts)的模式风速数据与反演获得的风速结果进行对比验证。结果表明,两者的相关系数较高(R=0.745),均方根误差和平均绝对偏差值分别为1.514 m·s-1和1.319 m·s-1。初步实验结果表明,利用MISR多角度光学遥感影像估算海表面风速是可行性的。 相似文献
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海面发生大面积溢油事故时,由于太阳耀斑区的存在,海面的油膜在遥感影像上会发生明暗的变化。这对溢油的检测会产生严重的干扰。如何在海面太阳耀斑区准确地检测出溢油是目前溢油检测的难题。针对这一问题,本文利用Landsat7 ETM+多光谱影像数据,开展了基于卷积神经网络(CNN)的海面太阳耀斑区溢油检测方法研究。通过设置对照实验,对比支持向量机、最大似然、随机森林等分类方法,我们发现在相同实验条件下CNN模型的分类精度为95%～99%, Kappa系数为0.92～1,均高于其他三种分类方法,表明了CNN模型在海面太阳耀斑区溢油的检测具有更高的精度与一致性。 相似文献
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2018-01-17—03-11,在大连长兴岛附近海域开展了为期54d的水文和气象连续现场观测,获取了风速、气温、海流、波浪、海冰、以及水体回声强度等多要素观测数据。数据显示观测期间经历了2次完整的大风降温天气过程(寒潮),并且在降温后出现了显著的冰情。通过将回声强度数据转化为后向声散射强度,用后向声散射强度数据表征水体悬浮物浓度变化,利用EMD方法分解了后向声散射强度数据,分析了潮流和波浪在海面是否结冰情况下对沉积物再悬浮的影响。结果显示:海面结冰对潮流引起的海底沉积物再悬浮没有明显影响,但海冰却能通过抑制波浪来减弱沉积物的再悬浮。 相似文献
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光学遥感图像中光斑区的出现是不可避免的,以MODIS为代表的中分辨率光学遥感器具有更宽的覆盖宽度,其耀斑区范围更大。耀斑区虽然对于传统的水色遥感是噪声,但对于海洋内波等动力过程的观测却是非常有益的。由于耀斑区的亮度远大于其它,因此为了观测整景图像范围的内波需要进行均衡化处理。本文以MODIS图像为例,发展了基于多项式函数的拟合方法,较好的实现了图像的均衡化处理,处理后的图像亮度变化均匀,可以清楚的观测整景图像各个部分的内波,而不需要逐一进行图像增强。 相似文献
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对Radarsat-2和Sentinel-1A分别观测的两个海域的单景SAR图像进行子孔径分解,各自得到不同方位角上的两幅SAR子孔径图像。使用多普勒质心频移法分别对不同方位角的两幅SAR图像进行海流反演,并进行海流矢量合成,采用经过时空匹配的HYCOM模式数据对反演结果进行检验,结果表明：Radarsat-2观测的SAR图像分解的两幅子孔径SAR图像矢量合成后的海流与HYCOM模式数据相比,速度均方根值为0.09 m/s,相关系数为0.64;方向均方根值为10.49°,相关系数为0.78。Sentinel-1A观测的SAR图像分解的两幅子孔径SAR图像矢量合成后的海流与HYCOM模式数据相比,速度均方根值为0.06 m/s,相关系数为0.82;方向均方根值为2.85°,相关系数为0.86。由此可见,基于单景SAR分解的两幅子孔径SAR图像可以有效反演二维海流。其反演精度与雷达视向和真实海流矢量的方向有关,二者的角度越小,反演海流矢量的精度越高。 相似文献
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用合成孔径雷达图像反演浅海水下地形的一种方法 总被引：2，自引：0，他引：2
海流与海底地形的相互作用导致了海表面的粗糙起伏,从而引起对海面观测的雷达散射截面的变化。在浅海海流速度垂直分布廓线为均匀的假定下,由流体连续性方程和驰豫时间近似下流体力学弱相互作用的理论,已证明雷达散射截面的空间变化正比于海流方向上海流速度变化的梯度。研究了合成孔径雷达(SAR)对海面的观测图像在无槽道信息和海流方向预知条件下,提出用散射系数的二维相关函数确定海流方向。在海流速度和方向已知条件下,推导了由雷达散射截面的空间变化迭推反演浅海水下地形的公式,并研究了航天飞机SIR-CSAR在我香港特区海域的二维图像反演浅海水下地形的应用。 相似文献
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在合成孔径雷达(Synthetic Aperture Radar,SAR)海面风场反演中,基于风条纹影像纹理特征的海面风向反演方法精度高,但是依赖于图像风条纹的存在,而外部风向信息与SAR资料时空分辨率不易匹配、精度较低,从而影响大面积、高分辨率海面风场反演的精度。针对此问题,提出一种将SAR图像风条纹线性纹理特征与外部风向信息相结合的星载SAR海面风向获取方法,在SAR影像线性纹理特征明显的区域采用二维连续小波变换得到高精度的海面风向,其余区域采用与之时空相匹配的数值预报模式风向填充;并利用地球物理模型函数进一步得到海面风速,进而实现高精度、大范围海面风场的反演。为验证本文方法的有效性,利用ENVISAT/ASAR数据进行风场反演试验,并将反演结果与浮标实测数据进行比对。结果表明:在线性纹理特征明显的区域,小波方法的反演精度优于快速傅里叶变换(FFT)法和数值预报模式风向;外部风向精度略低,但与SAR观测资料时空匹配性较好,弥补了风条纹风向的不足。二者的结合为星载SAR海面风场反演的业务化应用提供了支持。 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges. 相似文献
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A vertically integrated model has been used to study the tidal circulation and currents in the Gulf of Kachchh along the west coast of India. The model is fully nonlinear and uses a semiexplicit finite difference scheme to solve the basic hydrodynamic equations on a staggered grid. The model is forced by prescribing the tides along the open boundary of the model domain. The flow is simulated both with and without the presence of the proposed tidal barrage across the Hansthal Creek in the Gulf of Kachchh. The results show a considerable change in the behavior of the tidal flow in the presence of the barrage. 相似文献
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利用中国GF-3卫星SAR和HY-2A卫星微波散射计的首次台风联合定量观测 总被引：4，自引：0，他引：4
<正>The typhoon,as a mature tropical cyclone that develops in the western part of the North Pacific Ocean with high wind speed and heavy rainfall,is one of the most lethal and costly of natural disasters for the densely populated countries of East Asia.It can be easily detected by space-borne sensors operated at microwave,visible or infrared bands(Liu et al.,2014).Synthetic Aperture Radar(SAR)is 相似文献
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Soil core samples fromRhizophora mangleL. andAvicennia schauerianaStapf & Leech forests from south-eastern Brazil were analysed for their total organic matter content and their sugars, amino acid and amino sugars composition. Organic carbon and nitrogen contents were higher inAvicenniathan inRhizophorasoils. The contribution of sugars and amino acids to the total organic carbon pool was constant with depth inRhizophorasoils whereas inAvicenniasoils it increased. Spectral distribution of sugars and amino acids showed a dominance of Ca-affine monomers, particularly acidic amino acids, and the sugar arabinose. Biogeochemical indicators derived from ratios of individual sugar and amino acid monomers confirm previous studies which showed that organic matter in both soils is mainly of mangrove origin. The results further suggest accumulation of organic matter inRhizophorasoils and a continuing degradation of organic matter inAvicenniasoils. The latter may thus release more nutrients to adjacent ecosystems thanRhizophorasoils. 相似文献
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《African Journal of Marine Science》2013,35(1):181-203
Orange roughy Hoplostethus atlanticus are unusual fish. They form dense aggregations that have fuelled lucrative fisheries at great depths (600–1 400 m), especially off Namibia, New Zealand and Australia. They are thought to be very long-lived (>100 years, maturity at 22 – 40 years), and to have exceptionally low natural mortality (M = 0.045–0.064 year?1) and slow growth rates (K = 0.055–0.070 year?1). In addition, they spawn large eggs and have low fecundity. These factors combine to make orange roughy highly susceptible to overfishing; most stocks are below 30% of pristine levels. Assessments are obtained from indices of catch rate and trawl, acoustic and egg surveys. Acoustic estimates are the most direct, but are confounded by the species' low target strength (?50 to ?53 dB)–attributable to the wax-filled swim bladder. Extracellular wax esters are stored in abundance and comprise mostly mono-unsaturated fatty acids, with low concentrations of the ω-3 fatty acid family. This unusual composition (resultant from the species' diet) ensures neutral buoyancy. Stock separation has been inferred mainly from biological studies, but genetic studies have also found differences among stocks within New Zealand and Australia. Deep-water habitat may be damaged by trawling operations and may take many years to recover, so in some quarters there is a call for a portion of suitable habitat to be set aside for preservation. Although Namibian orange roughy are shallower, smaller and younger than those in other stocks, the Namibian fishery sustained high catches for only a few years before quotas were reduced, from 12 000 to 1 875 tons. Three management lessons are suggested for developing orange roughy fisheries based on the Namibian experience: (1) imposition of catch limits during exploratory fishing; (2) starting the acoustic surveys earlier in the fishery, if possible; (3) greater reliance on trends in catch rate until a survey series has been established. 相似文献