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水下滑翔机其通过集成生物、化学、物理传感器可以测量如温度、盐度、溶解氧等多种海洋基础水文要素,其利用卫星定位系统获得实际出水速度和理论出水模型获得理论出水速度之差可以计算深度平均流,。本文利用海翼水下滑翔机获得温盐场及卫星定位数据评估深度平均流,结果显示利用温盐场获得深度平均地转流与水下滑翔机获得深度平均流相关系数0.95,表明其流场的一致性,同时根据船载观测ADCP误差分析法估算深度平均流误差约为0.036 m/s。借助深度平均流可以估算绝对地转流,包括正压地转流和斜压地转流。在零动力面的假设下,我们选取了海翼号水下滑翔机在南海的一组实验对流量误差进行了评估。该实验为2019年1月3日-2月16日海翼号水下滑翔机自南向北穿越西沙群岛附近一个中尺度涡观测。观测结果表明,该中尺度涡为冷涡流核,在涡心以南,绝对地转流为东向流,最大流速约为0.48 m/s;涡心以北,绝对地转流为西向流,最大流速约为0.47 m/s,稍弱于南侧。受不均匀时空观测计划影响,本文未对流量做出估计。 相似文献
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受浑浊水体自身吸收与微颗粒散射的影响,水下光学成像面临成像距离短、像质差等问题。一种基于斯托克斯参量的主动偏振成像模型被应用到水下成像去散射过程中,有效提升了目标成像探测的清晰度。相比于被动偏振成像模型,引入主动光源可以实现对入射光的偏振调制,由此可以充分挖掘目标反射光与介质光的偏振特征差异进而实现分离选通。改进的主动偏振去散射模型利用了目标反射光的偏振共模抑制效应,借助偏振斯托克斯参量 S2 分量实现了介质光偏振角与偏振度全局分布的准确估算。同时引入图像质量评价参数对比度 contrast 作为反馈参量,通过迭代计算实现背景噪声的最大化滤除。不同散射程度、不同类型目标的水下成像实验表明：相比于传统主动偏振成像方法,改进后的成像模型可大幅提升水下目标的图像质量,特别是强散射环境下的图像 contrast 提升超 2 倍以上。该项工作为利用偏振信息进行水下图像去散射与目标重建提供了新思路。 相似文献
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众多海洋观测数据表明,在真光层深度范围内,海水固有光学特性和光学有效组分的剖面分层分布是广泛存在的,而很多遥感反演模型的建立基于均一分布假设,尤其是在经验模型的建立中,往往只利用某一深度或各深度平均的光学有效组分浓度与水体光谱的统计关系。文章通过模拟平静水面水下光的辐射传输,分别研究了叶绿素、无机悬浮物浓度垂直分布结构对水下辐照度比的影响,并对比了两类分层水体权重函数等效浓度计算式及相应水下辐照度比,结果表明,对于分层水体,透射深度和层化强度是影响等效浓度值计算误差的主要因素,透射越深,表层层化越强,水体层化对水下辐照度比的影响就越大,但其计算误差也越大。Gondon等效浓度计算结果比较接近实际值,而Zaneveld计算式则高估了分层水体的等效浓度值。 相似文献
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人工神经网络方法估算海洋上混合层深度的初步研究 总被引：1，自引：0，他引：1
上混合层深度是海洋上层热力结构特征的重要参数.结合南海南部海区一连续温盐深观测站的实测资料和NCEP再分析风场资料,以海洋表层温度和风应力为输入,以温度差值判断方法计算所得上混合层深度为输出,采用BP神经网络和广义回归神经网络2种方法进行训练,建立了南海南部海区的上混合层深度人工神经网络计算模型.实验显示,两种模型仿真结果与温度差值方法计算结果均方根误差分别为3.58m、3.09m,线性相关分别达0.87、0.91,绝对误差分别为2.80m、2.37m,相对误差分别为9.40%、7.40%.这一结果表明,人工神经网络方法精度较高,是一种切实可行的上混合层深度估算方法. 相似文献
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在将钻井垂直地震剖面(VSP)数据的时深拟合公式应用于深部地层的时深转换时,拟合深度与计算的层速度常常不够准确。本文首先利用多项式和幂函数给出了东海陆架盆地中部某凹陷41口钻井VSP数据的时深拟合公式,并用双程旅行时(TWT)最深达8 s的三维地震速度体数据与多道地震剖面对拟合公式在深部地层的适用性进行分析。在TWT为8 s时,速度体数据表明41口钻井位置的平均深度为18 140 m,平均层速度为6 208 m/s,二次多项式的平均拟合深度较之偏高9.2%,计算的层速度偏高36.2%,幂函数则分别偏低28.9%与35.6%,拟合效果都不理想。对此,本文采用通过识别VSP数据的增速拐点并对增速拐点前的VSP数据进行二次多项式拟合,对增速拐点后的VSP数据进行幂函数拟合的分段拟合模型,将TWT为8 s时的平均拟合深度和层速度的误差降到3.3%与4.7%。地震剖面显示研究区莫霍面深度约为TWT=11 s,分段拟合模型在TWT=11 s的平均拟合深度为27 516 m,层速度为7 334 m/s,更接近前人研究成果,表明该模型能显著提高深部地层时深转换的精度。 相似文献
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由于水介质的吸收和散射特性会导致雾化、低对比度、颜色退化等各种水下成像失真,严重影响了水下图像的后续利用。为了恢复清晰的水下图像,提出一种基于改进生成对抗网络的深度学习模型。借助图像质量评价技术,将生成的过程样本与高质量样本进行拟合,并将拟合得到的差值信息用于优化网络中的生成器。改进的生成式对抗网络有效改善了由真假训练逻辑带来的图像质量提升限制的问题。实验结果显示：该方法有效的恢复了水下图像的色彩,并改善了图像的清晰度和对比度;相比其他方法,提出的方法在 SSIM、UCIQE 和 UIQM 指标上分别提升了 2.9%、6.2%和 14.3%。 相似文献
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浅海水下地形的SAR遥感仿真研究 总被引：2，自引：0，他引：2
结合连续性方程和布拉格后向散射模型,在准一维简化浅海水下地形情况下,建立了浅海水下地形SAR海面相对后向散射强度仿真模型,将浅海水下地形区域的SAR海面后向散射强度的相对变化与大尺度背景流场、海面风场和雷达系统参数等联系起来.海上实验和研究结果表明,浅海水下地形的SAR成像主要由通过受水下地形影响的海表层流场对海表面风引起的微尺度波的水动力调制而获取浅海水下地形信息,其中潮流与水下地形的相互作用过程改变海表层流场,变化的海表层流与海表面微尺度波之间的相互作用改变海表面波的空间分布,雷达波与海表面波之间的相互作用决定雷达海面后向散射强度.因此SAR图像中浅海水下地形或水深信息量的多少不仅与海表层流场和海面风速有关,而且与雷达工作波段、雷达波束入射角和极化方式也密切相关.认为由水下地形变化引起的缓慢变化的表层流场中海表面定常微尺度波谱能量密度的变化满足波作用量谱平衡方程;而在波数空间中,海表面微尺度波谱的成长过程也可以用波数谱平衡方程描述,在此基础上,得出了海表面波高频谱(毛细-重力波)形式的解析表达式.众所周知,浅海水下地形信息是由于水下地形影响下SAR海面后向散射强度与背景海面后向散射强度的相对差异而在SAR图像上的呈现,从而在建立浅海水下地形SAR海面相对后向散射强度仿真模型的基础上,仿真计算了浅海水下地形SAR海面相对后向散射强度相对于海表层流场、海面风场等海况参数和SAR工作波段、SAR波束入射角、极化方式等雷达系统参数的数值仿真结果,分析得到了有关浅海水下地形SAR海面相对后向散射强度的特征和SAR浅海水下地形遥感的最佳海况参数与最佳雷达系统参数,为研究和开展SAR浅海水下地形遥感研究提供了有价值的参考. 相似文献
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A. G. Petrushin 《Izvestiya Atmospheric and Oceanic Physics》2016,52(3):257-262
Key optical characteristics of radiation scattering in clouds (mean cosine of the scattering phase function, averaged factors and indices of scattering efficiency, and single-scattering albedo) and integral characteristics of homogeneous cloud layers (cloud-layer albedo and transmission factor) have been calculated with the use of the earlier suggested model of the microstructure of mixed phase clouds, where ice crystals and water droplets are homogeneously mixed over the volume, for individual wavelengths in the range from 0.6 to 10.6 μm. An approach is elaborated for statistically valid parameterization of the above characteristics versus the mean temperature of a mixed layer only under the availability of reliable information about the temperature dependence of the characteristic sizes of particles of different fractions and their concentrations in the cloud. 相似文献
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基于浮标站海浪历史数据,利用回归分析方法建立了海浪数值模式有效波高预报产品的一元二次回归方程订正统计模型。通过2017年7月1日-2018年10月10日期间业务试运行结果发现:订正方程能有效改善有效波高数值预报产品的预报精度,且预报时效越短订正效果越显著。其中,第6~11 h预报时效内的订正前后平均绝对误差值减小0.17~0. 241 m,第6~18 h预报时效内订正前后均方根误差减小幅度为0.103~0. 28 m。这说明应用订正统计模型对海浪模式输出产品进行订正,也是改进海浪模式预报准确率的一种有效途径。 相似文献
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The availability of an equation to evaluate the influence of multiple scattering in the single scattering process corresponding
to a layer of arbitrary optical thickness was established. In order to confirm the validity of this equation, the radiance
distribution in this layer was computed using a plane–parallel layer model based on the successive order of scattering method.
The relative errors in a radiance distribution computed were evaluated as a function of optical thickness by the derived equation.
It was shown that this equation provides a theoretical background for determining layer thickness using the plane–parallel
layer model. 相似文献
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Replacing traditional light sources with light-emitting diode (LED) light modules is a global trend, especially for underwater illumination. The light intensity is dispersed evenly at all emission angles in traditional underwater light sources that use the radiative transfer model, resulting in the inclusion of scattering factors in the attenuation coefficient. The high directionality of LED light source modules causes the light intensity transfer in water to vary according to varying emission angles. This renders traditional underwater optical transfer theory irrelevant as an underwater LED light module design reference. Therefore, this study constructs an underwater LED light source transfer model using the light-field average cosine and the light transfer scattering probability method, and imports the LED luminous intensity distribution curve (LIDC) and axial luminous intensity. Experimental results showed that the illumination intensity of the underwater LED illumination module was less than 10% of the simulation. Therefore, this design method can be used to design the required illumination light modules for different underwater environments. Finally, the LED light module has been used for under water fish attractor lighting and enhanced the illumination zone efficiency (m3 per Watt) of 81% compared to the traditional high intensity discharge (HID) underwater fish attractor lamp. 相似文献
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Gorodetskaya E.Yu. Malekhanov A.I. Sazontov A.G. Vdovicheva N.K. 《Oceanic Engineering, IEEE Journal of》1999,24(2):156-171
This paper presents results of combined consideration of sound coherence and array signal processing in long-range deep-water environments. Theoretical evaluation of the acoustic signal mutual coherence function (MCF) of space for a given sound-speed profile and particular scattering mechanism is provided. The predictions of the MCF are employed as input data to investigate the coherence-induced effects on the horizontal and vertical array gains associated with linear and quadratic beamformers with emphasis on the optimal ones. A method of the radiation transport equation is developed to calculate the MCF of the multimode signal under the assumption that internal waves or surface wind waves are the main source of long-range acoustic fluctuations in a deep-water channel. Basic formulations of the array weight vectors and small signal deflection are then exploited to examine optimal linear and quadratic processors in comparison with plane-wave beamformers. For vertical arrays, particular attention is paid also to evaluation of the ambient modal noise factor. The numerical simulations are carried out for range-independent environments from the Northwest Pacific for a sound frequency of 250 Hz and distances up to 1000 km. It was shown distinctly that both signal coherence degradation and modal noise affect large-array gain, and these effects are substantially dependent on the processing technique used. Rough surface sound scattering was determined to cause the most significant effects 相似文献
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The characteristics of directional spread parameters at intermediate water depth are investigated based on a cosine power ‘2s' directional spreading model. This is based on wave measurements carried out using a Datawell directional waverider buoy in 23 m water depth. An empirical equation for the frequency dependent directional spreading parameter is presented. Directional spreading function estimated based on the Maximum Entropy Method is compared with those obtained using a cosine power ‘2s' parameter model. A set of empirical equations relating the directional spreading parameter corresponding to the peak of wave spectrum to other wave parameters like significant wave height and period are obtained. It shows that the wave directional spreading at peak wave frequency can be related to the non-linearity parameter, which allows estimation of directional spreading without reference to wind information. 相似文献
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Hamilton-type geoacoustic models were developed for Area Foxtrot, a shallow water test bed south of Long Island, for emerging active sonar systems where the surface sediment type is highly spatially variable. Reverberation levels (RL) were modeled using the finite-element parabolic equation (FEPE) propagation model to augment the generic sonar model (GSM) propagation model because the bottom loss model in GSM did not estimate transmission loss (TL) accurately in shallow water. FEPE estimates reveal that there is a greater than 15 dB difference between TL for sand and that for silt-day sediments in Area Foxtrot. The comparison between modeled RL and measured RL (from a 1991 active sonar exercise) enabled bottom scattering strength kernels to be developed for Area Foxtrot. Bottom scattering strength was found to be a function of sediment type. Hard sand sediment has a bottom scattering strength which obeys Lambert's law (sin2 &thetas;) while that of silt-clay sediment is consistent with sub-bottom volume scattering (sine). The RLs in Area Foxtrot are azimuth-dependent and are a function of TL and bottom scattering strength (and hence bottom sediment type). Sonar beams steered towards the hard sand show higher RLs than for silt-clay, and knowledge of the sediment type and its spatial variation must be known to model RL accurately. A method to determine sediment type using measured RLs and RL slopes is given 相似文献
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Hitoshi Kawabata Hisashi Narita Koh Harada Shizuo Tsunogai Masashi Kusakabe 《Journal of Oceanography》2003,59(5):651-661
Thirteen vertical profiles of 226Ra and 222Rn in the near-surface water were obtained in the western North Pacific in winter, and the gas transfer velocities across
the air-sea interface were estimated. The transfer velocities found by applying a steady state model varied widely from 2.1
to 30.2 m day−1 with a mean of 9.4 m day−1. The mean value is almost 5 times higher than that in summer in other oceans, and the maximum value is a record high for
world oceans. This is partly due to the inadequacy of the steady state model, which overestimates when stronger winds blow
in more recent days than the 222Rn half-life of about 4 days. In fact, a strong low pressure zone passed through the station about 2 days earlier, which was
one of the low pressure zones that with a period of develop once a week or so in the northwestern North Pacific in winter.
Instead of steady-state removal, if half of the radon removal occurred sporadically every 7 days, and the last removal took
place two days before the observation, the transfer velocity would be 26 m day−1. Our mean transfer velocity, which is less than 20% different from the steady state value including both overestimated and
underestimated values, 9.4 ± 4.8 m day−1, seems to represent the mean state of this region in winter. This suggests that the gas exchange fluxes under extremely rough
conditions in the open ocean are larger than those estimated by using a transfer velocity equation with a linear or quadratic
relationship with wind speed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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S. G. Demyshev 《Physical Oceanography》1992,3(2):155-158
Approximation of the hydrostatics equation is considered using a state equation in the form of a quadratic polynomial of temperature and salinity. It is shown that in this case the traditional approximation fails to obey the law of energy conservation in the numerical model. A difference analogue to the hydrostatics equation is derived which has the required property. The results of the calculation are presented.Translated by V. Puchkin. 相似文献
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V. I. Mankovskii 《Izvestiya Atmospheric and Oceanic Physics》2016,52(3):328-333
A semiempirical model is constructed for the relationship between the coefficient of asymmetry of Light Scattering phase function in water K and the scattering coefficient σ, which shows a mechanism of an increase in the asymmetry coefficient as the scattering coefficient grows as a result of an increase in the concentration of organic particles. The mechanism of this relationship lies in the presence in all natural waters of molecular scattering and scattering by mineral particles that create background scattering in water medium, which is overlaid by scattering by organic particles. This relationship has a regional character caused by the regional features of background scattering and the average size of organic particles in those regions. The model relationships K = f(σ) are plotted properly to the experimental ones in the various regions. 相似文献