北印度洋风浪场特点及最佳航线分析

对１９８０－１９９０年北印度洋气象船舶报资料,按２°×２°网格进行了分析。通过分析研究阐明了北印度洋风,浪,涌的特点及其变化规律,这一海区是世界名的季风气候区,季风时期的风向,风浪传播方向,涌浪传播方向基本一致,夏季的西南季风比冬季的东北季风要强盛得多;大浪大涌频率高达８０％－９０％,该海域与南海属同一类型,但特点正好相反,按照船舶航行的对水气象条件的要求,横穿北印度洋时间以季风转换月份为最佳     

北大西洋风场和海浪场特点分析

根据1950～1995年共46a的北大西洋气象船舶报资料,对按5°×5°网格统计的风、浪要素进行分析研究,阐明了北大西洋风、浪、涌的特点及其变化规律.该区是世界典型的季风气候区,季风时期的风向、风浪传播方向、涌浪传播方向基本一致,低纬地区常年盛行东北浪.冬季季风比夏季季风强盛,相应的平均波高、大浪大涌频率也较大.该海域与北印度洋同属季风气候区,但其特点正好相反.本文提供了较翔实的风场和浪场资料及变化规律.     

北印度洋气候特点分析

根据1950～1995年共46a的北印度洋气象船舶资料,按5°×5°网格统计单元,绘制了历年各月风向频率、平均风速、6级和8级大风、能见度(≥10km和≤4km)、雾和雷暴等气象要素分布图.较为详细地分析了北印度洋风、能见度、雾、雷暴、热带气旋等海洋气象要素的分布特点及其年变化规律.该区是世界著名的季风气候区,夏季的西南季风比冬季东北季风强盛,与我国南海海区的季风特点正好相反.     

南印度洋海浪场时空特征分析

根据 1950 —1995 年共 46 a 的南印度洋船舶气象报资料，按 5°×　5°网格统计的海浪要素进行分析研究。通过分析每月各要素的等值线分布图，得出南印度洋海浪场季节变化特点不如北半球各大洋显著，但仍有较明显的季节变化，只是季节性差异较小，冬季比夏季海浪强盛，相应的平均波高、大浪大涌频率也较大；盛行风浪传播方向、涌浪传播方向基本一致，10°S 以北为季风气候区，而其它海域则信风区常年盛行 SE 向浪，40°S 以南盛行偏 W 向浪。本文提供了南印度洋海域较为翔实的海浪场资料及变化规律。     

西北太平洋风场和海浪场特点分析

本文根据1950～1995年共46a的西北太平洋气象船舶报资料,按5°×5°网格统计的风、浪要素进行分析研究,阐明了西北太平洋风、浪、涌的特点及其变化规律。该区是世界最典型的季风气候区,季风时期的风向、浪向、涌向基本一致,赤道地区常年盛行东北浪。冬季季风比夏季季风强盛,相应的平均波高、大浪大涌频率也较大。该海域与北印度洋同属季风气候区,但其特点正好相反。本文为船舶在西北太平洋航行、作业和科学试验以及军事活动,提供了较翔实的风场和浪场资料及变化规律。     

35°S以北的印度洋的气候状况和季风特征

３５°Ｓ以北的印度洋位于热带和副热带,北印度洋和印度次大陆及东南亚是全球最显著的季风气候区。北印度洋冬季为东北季风控制;但由于青藏高原阻断了冷空气,没有寒冷天气夏季风在南亚和东南亚陆上主要表现为暴雨,在北印度洋上主要表现为强劲的西南风;特别是在阿拉伯海的索马里急流区,夏季经常有６￣８级以上的西南大风。在春秋季的季风过渡季节,北印度洋时有台风发生,强风暴潮给孟加拉国造成极大的灾难。在春秋季的季风过渡     

北太平洋海浪场时空变化特征分析

根据1950—1995年共46a的北太平洋船舶气象报资料,对按5°×5°网格统计的海浪要素进行分析,阐明了北太平洋浪、涌的特点及其变化规律。该区赤道地区常年盛行东北浪,冬季海浪比夏季强盛,相应的平均波高、大浪大涌频率也较大。该海域与北印度洋同属季风气候区,但其特点正好相反。     

南印度洋风场时空特征分析

本文根据1950～1995年共46a的南印度洋船舶气象报资料,按1°×1°和5°×5°网格统计的海面风进行分析研究。通过分析每月各要素的等值线分布图,得出南印度洋风场季节变化不如北半球各大洋显著,但仍有较明显的季节变化,只是季节性差异较小,冬季比夏季风强盛,相应的平均风速、6级和8级以上大风频率也较大;全年风场基本相似,10°S以北为季风气候区,而其它海域信风区常年盛行东南风,40°S以南盛行偏西风。本文为船舶远洋交通运输、远洋出访和科学试验等活动,提供了较为详细的风场资料及变化规律。     

大西洋海表温度异常与中国东北地区夏季降水的关系

利用1950～1992年全球海温月平均(2°×2°)和NCAR/NCEP提供的1950～1997年全球500hPa月平均高度场(2.5°×2.5°)资料，分析了大西洋海表温度异常的特征及其与中国东北地区夏季降水的关系。结果指出北大西洋冬季海表温度经验正交展开的第二特征向量表明，海表温度的距平分布有南北差异的异常特征；其中心位置和中国东北地区夏季降水与冬季大西洋海表温度相关显著区中心基本重合北大西洋冬季海表温度出现南暖北冷异常时，同期北大西洋中高纬度地区的阻塞形势偏强，与之相对称的北太平洋北部的阻塞高压也偏强，对应来年夏季东亚西风环流指数偏低，造成东北区夏季降水偏多；反之亦然。     

大西洋海表温度异常与中国东北地区夏季降水的关系

本文利用1950～1992年全球海温月平均(2°×2°)和NCAR／NCEP提供的1950～1997年全球500hPa月平均高度(2．5°×2．5°)资料,分析了大西洋海表温度异常的特征及其与中国东北地区夏季降水的关系。结果指出北大西洋冬季海表温度经验正交展开的第二特征向量表明海表温度的距平分布有南北差异的异常特征其中心位置和中国东北地区夏季降水与冬季大西洋海表温度相关显著区中心基本重合;北大西洋冬季海表温度出现南暖北冷异常时,北大西洋中高纬度地区的阻塞形势偏强,与之相对称的北太平洋北部的阻塞高压也偏强,对应夏季东亚西风环流指数偏低,造成东北地区夏季降水偏多。     

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,     

Evaluation of the Risk of Marine Slope Instability: A Pseudo-3D Approach for Application to Large Areas

This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed.