Wavewatch Ⅲ模拟和统计方法在最大波高预报方面的评测分析

为了研究Wavewatch Ⅲ(WW Ⅲ)海浪模型对最大波高的模拟能力及其与传统统计关系方法的差异,通过对两次台风浪过程的后报模拟和半年的业务化预报,分析了WW Ⅲ数值模拟的准确度及其与统计关系方法的精度差异。研究结果表明：WW Ⅲ数值模拟的最大波高(H_max)的精度略低于有效波高(Hs),但也达到了24 h预报相对误差(H_max≥1 m)低于18%、相关系数高于0.94的水平,模拟精度可靠,可以用于业务化预报;与两种统计关系方法(H_max和Hs分别为1.42和1.52)计算的最大波高相比,数值模拟的精度总体与其相当,但在H_max和Hs比值大于1.65这种易出现危险的海况下,数值模拟具有更高的准确性,更适合应用于海浪预警报服务。     

基于雷达高度计增益自动控制数据的风速反演算法研究

基于Jason-1卫星雷达高度计与NDBC(National Data Buoy Center)浮标的时空匹配数据集,利用BP(Back Propagation)神经网络方法建立了基于后向散射系数σ₀与有效波高(Significant Wave Height,SWH,)的双参数(σ₀-H_sw)风速反演模型,并探讨利用AGC(Automatic Gain Control)来代替σ₀对风速反演的可行性进行研究。结果表明,所建立的σ₀-SWH风速反演均方根优于0.3 m/s(风速范围为0.5~20 m/s); AGC-SWH模型反演精度偏低(1.3 m/s),但在星星交叉定标的基础上,模型精度提高了0.9 m/s。这个研究工作尤其是交叉定标基础上的AGC-SWH模型反演流程对"HY-2"海面风速反演有一定的借鉴意义。     

X-波段雷达近海海浪频谱反演的神经网络模型

X-波段雷达作为国内海浪观测的一种新工具,在海浪频谱获取和有效波高反演方面仍存在较多问题.本文利用非线性回归方法,将现场实测浮标数据频谱和雷达一维图像谱分别与标准频谱模型进行拟合,发现浮标频谱和一维图像谱具有标准频谱的特征,能够较准确地获取相应的谱参数.提出了建立由雷达一维图像谱参数反演海浪频谱参数的神经网络模型,同时在模型中加入影像序列信噪比,进而反演有效波高,并将反演结果与现场实测数据和传统算法(建立影像序列信噪比与有效波高之间的线性回归方程)进行了对比,结果表明,获取谱参数的误差和反演有效波高的平均误差在20％以内,而传统算法计算有效波高平均误差在20％以上.     

Jason-2有效波高产品在中国海域的准确性评估

Jason-2卫星高度计的有效波高(Hs)产品在海洋学领域得到了广泛应用。为了综合评估Jason-2有效波高产品在中国多个海域和不同海况下的准确性,为其在中国海域的应用研究提供参考,本文基于国家海洋局20个水文气象浮标从2008年至2014年的长期观测数据,对Jason-2有效波高产品在中国三个海区(渤黄海、东海、南海)和不同海况(观测有效波高Hs最大为6.2m)下的准确性进行综合分析,并研究其准确性与离岸距离的关系。结果表明Jason-2有效波高产品:(1)在中国海域具有较好的准确性,均方根误差RMSE=0.445m;(2)在南海的准确性最高,而在渤黄海的准确性较差;(3)在2m≤Hs≤5m的海况条件下准确性较好;(4)在越远离陆地的海域准确性越高。     

降雨条件下的导航X波段雷达海浪参数反演算法研究

X波段的电磁波受降雨影响容易产生衰减,这导致导航X波段雷达在降雨时无法用于海浪观测。本文提出了一种新的降低降雨影响的算法来反演海浪参数。首先,对X波段雷达图像做主成分分析,获得波浪变化的主成分,利用一维傅里叶变换得到波数谱,对其滤波减小降雨对雷达图像的影响;然后,选取JONSWAP(Joint North Sea Wave Project)谱作为理论谱,建立以观测谱与理论谱的最小化差异为目标函数的模型,求解该模型估算海浪的有效波高。与浮标测量的有效波高相比,该方法反演的有效波高的均方根误差是0.23 m,证明了该方法的可行性。     

黄东海春季水体后向散射系数的经验模型研究

水体后向散射系数的反演模型研究是 II类水体生物 -光学算法开发的重要组成部分。通过对 2 0 0 3年 4月黄东海试验获得的水面之下遥感反射率 rrs (λ)和后向散射系数 bb (λ)的分析 ,以 bb (4 1 2 )为中间变量 ,根据水体后向散射系数的光谱特点 ,统计获得了 rrs (λ)反演的统计模型。从整体反演的效果可见 ,该模型在试验水域可使 73%的样品反演相对偏差控制在± 30 %之内 ,且多集中于± 1 0 %之内     

HH 极化 Ter r aSAR-X 图像提取海浪要素的方法研究

把 SAR 海面风场反演的地球物理模型与海浪的参数化初猜谱反演模式结合起来,用于提取 Ter r aSAR-X 图像的海浪 要素信息。首先采用风场反演的经验模型得到 Ter r aSAR-X 图像的海面风场,然后将风场信息作为初始条件应用于参数化初 猜测谱模式中,从而得到海浪谱以及相关的海浪要素信息。反演结果与对应的浮标站点数据进行对比,对比结果显示：风速 的绝对误差在 1. 1 m/ s以内,风向的绝对误差在 5毅以内,有效波高的绝对误差在 0. 93 m 以内,平均周期的绝对误差在 2. 43 s 以内。因此,可以得出结论：本文使用的方法能有效的从 Ter r aSAR-X 图像中提取海浪要素的信息。     

基于CDOM吸收系数的长江口DOC浓度反演模型的优化

卫星遥感的边缘海溶解有机碳(DOC)的时空分布对于厘清区域和全球碳循环具有重要意义。有色溶解有机物(CDOM)吸收系数[a_g(λ)]被广泛应用于构建边缘海DOC的卫星反演模型。不同的研究选择不同波长的a_g(λ),而不同波长的选择是否影响DOC反演结果的准确度却未见报导。针对此问题,本文以长江口为例,以2017年冬季、春季和夏季的调查数据为基础,探讨如何选择合适波长的a_g(λ)用于优化边缘海DOC的反演模型。首先,通过分析不同波长的a_g(λ)和DOC的相关性显示,当波长在250～385 nm时,a_g(λ)和DOC浓度呈现良好的线性关系(r~(2 )=0.67±0.01),DOC的均方根误差(RMSE=(25.1±0.5)μmol·L~(-1))也较小;随着波长的增大,两者之间的相关性急剧减弱,对应的RMSE也急剧增大。因此,DOC的反演宜选择波长小于385 nm的a_g(λ)。其次,通过分析a_g(λ)随波长的对数衰减关系显示,紫外波段的衰减速度通常要快于可见光波段。当以可见光波段的数据来拟合建立a_g(λ)随波长的对数衰减公式时,该公式可延伸用于估计波长大于380 nm的a_g(λ),其产生的误差通常在±5%以内;而对于波长小于380 nm的a_g(λ)则往往产生较大低估,且低估程度随波长减小而增大。因此,对于目前的水色卫星(未包含紫外波段),当使用可见光波段的遥感反射率[R_(rs)(λ)]通过GSM、QAA等模型进行反演时,对于波长大于380 nm的a_g(λ)的反演结果的置信度较高。综合上述分析,选择波长380～385 nm的a_g(λ)来构建长江口DOC的反演模型有利于降低反演结果的系统误差。长江口作为全球边缘海的典型代表,本研究的结果对于优化全球边缘海的DOC反演模型具有重要的指示意义。     

基于重叠正射影像的浅水水深测量方法

在立体影像双介质测量水深和多光谱影像反演水深的研究基础上,提出将两者集成的途径。在重叠正射影像的有纹理水域采用折射法获取水深值,将折射法获取的水深值作为多光谱反演模型的参考值,获取反演模型参数,将反演模型应用到无纹理水域,集成折射法和反演法的水深值,从而获取浅水区域的水下地形。以某浅海地区航空影像生成的左右正射影像为实验数据,采用折射法与反演法集成途径获取水深值,并与真值(激光水深点)进行回归分析,回归的决定系数(R~2)和均方根误差(RMSE)分别为0.9 m和0.45 m,验证了该集成途径的有效性和可行性。     

长江口附近海域周年波浪特征分析

本文利用长江口附近海域2011年1月—2011年12月长达1年的海浪实测资料,对海浪基本要素及大浪过程与热带气旋活动的关系进行统计分析,并选取一个典型台风过程的波浪进行研究。研究结果表明：观测点年有效波高H_s平均值为1.2 m, 1月平均有效波高H_s值最大,受台风影响,最大有效波高出现在8月,达7.4 m;观测期间,有效波高H_s多集中在2 m以下范围内,有效周期T_s在3～14 s之间;本地区的有效波高H_1/3和风速U₁₀具有较好的指数关系;强台风“梅花”活动期间,波型变化与一般台风浪波型的演变规律较为一致。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

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。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

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.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Estimation of Sediment Properties during Benthic Impact Experiments

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.