有风浪太湖水体的光照传输模式   总被引：8，自引：0，他引：8       下载免费PDF全文

蔡启铭  杨平 《海洋与湖沼》1993,24(3):286-293

根据辐射传输方程的近似解方法和光照传输的累加原理,建立了包括水面风浪效应、水中悬浮粒多次散射和底泥反射的垂直分层水体的光照传输数值模式。利用该模式和太湖悬浮粒实测资料,计算和讨论了太湖水体中光照随水深的变化以及悬浮粒浓度、风浪和太阳高度的影响。结果表明,悬浮粒的多次散射所形成的漫射光是湖水中光照不可忽视的重要部分。在水体的下层,漫射光甚至是光照的主要构成部分。风浪对水中光照的影响则主要在天顶角大于70°时才明显地表现出来,此时风浪水体对太阳直接辐射和全辐射的反射率比平静水面都有明显的减小。  相似文献   

南海波高熵和风速熵   总被引：4，自引：0，他引：4  

郭佩芳  施平  孙孚  戚建华 《海洋与湖沼》1997,28(2):185-191

根据风速的统计分布，给出了有因次风速熵和无因次风速熵的定义及其计算方法，使用ＧＥＯＳＡＴ高度计１９８６年１１月－１９８９年２月的有效波高和风速的资料，计算，分析了南海海域上的波高熵，风速熵，给出它们的时间变化特征和空间变化特征，并对不同随机量的无因次熵，即随机度进行了比较。  相似文献   

南海环境要素的年际变化与1982—1983年EI Nio     

柯东胜 《海洋与湖沼》1992,(4)

本文在大量调查资料的基础上,分析了1975—1984年南海环境要素的年际变化及其在1982—1983年的表现。研究发现,与正常年份比较,各要素在1982—1983年的表现都比较特殊,沿岸江河径流量猛增;气温、水温、盐度、pH值偏低;海水含氧量偏高,温、盐、密跃层强度增大;南海暖流和黑潮南海分支流轴的平均位置移到调查海区的最南面。作者认为,这一异常现象与1982—1983年赤道太平洋海域发生的强E1 Ni(?)o过程密切相关。  相似文献   

Seasonal and Spatial Variations of Iceberg Drift off Dronning Maud Land, Antarctica, Detected by Satellite Scatterometers   总被引：1，自引：0，他引：1  

Shigeru Aoki 《Journal of Oceanography》2003,59(5):629-635

Seasonal and spatial variations of iceberg drift were studied using continuous satellite scatterometer images off Dronning Maud Land, East Antarctica. Generally, iceberg drift speed showed a westward increase to the Greenwich Meridian. Seasonal variations of the drift speed were high in autumn—early winter and low in spring, and their magnitudes also increased westward. Seasonal variations of the drift speed were significantly correlated with variations of sea levels at Syowa and Mawson Stations, and hence qualitatively consistent with geostrophic current variations. Thus, the scatterometer data are demonstrated to be useful in monitoring iceberg trajectory and oceanic current variations. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Molecular identification of bloom-forming species Phaeocystis globosa (Pryninesiophyta) and its dispersal based on rDNA ITS sequence analysis     

Chen Yueqin  Shao Peng  Wang Ning  Zhou Hui  Qu Lianghu  Linda K. Medlin 《海洋学报(英文版)》2003,22(2):243-253

The colony-forming Phaeocystis species are causative agents of dense bloom occurrences in coastal waters worldwide. It is difficult to separate them because of the different morphologies associated with their colonial stages. In this study we applied molecular approaches to analyze the genetic variation of Phaeocystis globosa and Phaeocystis pouchetii from several geographic regions, and to assist in tracing the dispersal of bloom-forming Phaeocystis species in coastal waters of China. The sequences of the internal transcribed spacers (ITS1 and ITS2) of rDNA and the 5.8S ribosomal RNA gene of Phaeocystis strains were determined. Sequence comparison shows that P.globosa was the most divergent to P. pouchetii, exhibiting sequence divergence higher than 0.08. However, lower genetic divergences existed between strains of P.globosa. The sequence comparison of the Phaeocystis rDNA ITS clearly shows that the species isolated from the southeast coast of China is identified as P.globosa rather than P. cf. pouchetii or other species. Furthermore, the significance of rDNA variation in distinct global populations of P.globosa suggested it might have had sufficient time to accumulate detectable mutations at the rDNA locus, supporting the hypothesis of ancient dispersal of P.globosa to many areas, meaning that P.globosa blooms in the coastal waters of China are endemic rather than a newly introduced species or a foreign source. Finally, based on the high divergent region of rDNA ITS, a pair of species-specific primers for P.globosa were designed, they could be useful to detect the presence of this species in mixed plankton assemblages or flagellate stages that are recognized with diffculties by means of conventional microscopy.  相似文献   

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

Woojae Seong  Cheolsoo Park 《Marine Georesources & Geotechnology》2001,19(1):37-50

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.  相似文献   

Seasonal and annual variations of marine sinking particulate flux during 1993~1996 in the central South China Sea   总被引：1，自引：0，他引：1  

CHEN Ronghu  WIESNER M G  ZHENG Yulong  CHENG Xinrong  JIN Haiyan  ZHAO Qingying  ZHENG Lianfu 《海洋学报(英文版)》2007,26(3):33-43

A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993~1996. It is indicated that the distribution of stable isotope values, surface primary productivity, fluxes of total particulate matter, carbonate, biogenic opal, organic carbon, planktonic foraminiferal species and their total amount exhibit obviously seasonal and annual fluctuations. High values of the fluxes occurred in the prevailing periods of the northeastern and southwestern monsoons, and the low values occurred during the periods between the two monsoons. The fluxes of some planktonic foraminiferal species (Globigerinoides sacculifer, G. ruber, Globigerinita glutinata, Neogloboquadrina dutertrei) and their percentages also exhibit two prominent peaks during the prevailing periods of the northeastern and southwestern monsoons respectively, while those of Globigerina bulloides, Globorotalia menardii and Pulleniatina obliquiloculata only exhibit one peak in the prevailing periods of the northeastern monsoon. In addition, fluxes and percentages of Globigerinoides sacculifer and Globorotalia menardii as well as the fluxes of carbonate and total amount of planktonic foraminifera decrease gradually from 1993 to 1996, and those of Globigerina bulloides, Globigerinita glutinata and biogenic opal increase gradually from 1993 to 1996. The fluxes of carbonate and organic carbon in the upper trap are higher than those in the lower one. The study indicates that the seasonal and annual variations of the sediment fluxes and planktonic foraminiferal species are mainly controlled by the changes of surface primary productivity and hydrological conditions related to the East Asian monsoon. The lower carbonate and organic carbon fluxes in the lower trap are related to the dissolution.  相似文献   

Triple diagram method for the prediction of wave height and period   总被引：1，自引：0，他引：1  

Mehmet zger  Zekai en 《Ocean Engineering》2007,34(7):1060-1068

Many formulations have been developed so far to predict the wave height and period from fetch length and wind blowing duration for a constant wind speed. This study aimed to predict wave parameters from fetch length and meteorological factors by using triple diagram methodology based on Kriging principles. Proposed model results were compared with Joint North Sea Wave Project (JONSWAP) model which is used so commonly in the ocean and coastal engineering studies. For the implementation of the methodology hourly wave and wind data were obtained from a buoy located in Lake Ontario. Numerical and graphical comparisons demonstrated that the proposed method outperforms the classical formulation.  相似文献   

A note on the effects of a thin visco-elastic mud layer on small amplitude water-wave propagation     

Philip L.-F. Liu  I-Chi Chan 《Coastal Engineering》2007

In this note we investigated the effects of a thin visco-elastic mud layer on wave propagation. Within the framework of linear water-wave theory, analytical solutions are obtained for damping rate, dispersion relation between wave frequency and wave number, and velocity components in the water column and mud layer. The wave attenuation rate reaches a maximum value when the mud layer thickness is about the same as the mud boundary layer thickness. Heavier mud has a weaker effect on the wave damping. However, the wave attenuation rate does not always decrease as the elastic shear modulus increases. In the range of small values for elastic shear modulus, the wave attenuation can be amplified quite significantly. The current solutions are compared with experimental data with different wave conditions and mud properties. In general, good agreements are observed.  相似文献   

A linear Boltzmann equation to model wave scattering in the marginal ice zone   总被引：1，自引：0，他引：1  

Michael H. Meylan  Diane Masson   《Ocean Modelling》2006,11(3-4):417-427

We present a linear Boltzmann equation to model wave scattering in the Marginal Ice Zone (the region of ocean which consists of broken ice floes). The equation is derived by two methods, the first based on Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991] and second based on Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136]. This linear Boltzmann equation, we believe, is more suitable than the equation presented in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] because of its simpler form, because it is a differential rather than difference equation and because it does not depend on any assumptions about the ice floe geometry. However, the linear Boltzmann equation presented here is equivalent to the equation in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] since it is derived from their equation. Furthermore, the linear Boltzmann equation is also derived independently using the argument in Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991]. We also present details of how the scattering kernel in the linear Boltzmann equation is found from the scattering by an individual ice floe and show how the linear Boltzmann equation can be solved straightforwardly in certain cases.  相似文献