Microprocessor systems as an aid to estuarine studies in the laboratory

Three systems are outlined which indicate the potential of microprocessor systems as control devices in the generation of specifically varying environmental mental conditions. The use of an RCA 1802 Cosmac microprocessor to generate salinity cycles, tidal cycles and temperature cycles is described.     

潮滩生态系统中生源要素氮的生物地球化学过程研究综述

海岸带潮滩生源要素生物地球化学循环过程是国际地圈生物圈计划（IGBP）、海岸带陆海交互作用（LOICZ）研究的重要内容,也是全球变化区域响应研究中的重要组成部分。在过去的10～20年之间,潮滩生源要素氮的生物地球化学循环研究得到了长足的发展。基于此,较为全面、系统地总结和分析了有关潮滩氮营养盐的来源、潮滩氮素的物理、化学和生物迁移转化过程及氮素地球化学循环过程中底栖生物效应等一系列研究成果,并提出了今后潮滩生源要素氮的生物地球化学循环研究重点和发展趋向。     

从初始化中排除潮汐信号方案在全球模式中的应用

对国家气象中心全球预报模式T106L19原有的标准非绝热正规模初始化方案要求外强迫是准静止这一假定进行了修正,将潮汐信号在初始化条件中适当地表达出来并将其从中排除。与三维变分分析SSI的联接对比试验表明,修正潮汐信号后的新方案在消除高频重力波振荡方面与标准初始化方案有同样的效果,但该方案较标准初始化更好地捕捉住了地面气压的半日变化,更接近于未经初始化的分析场。模式7天预报500hPa高度场与分析场的对比检验表明,新方案的距平相关系数和均方根误差都较原方案有明显的改进。     

Tilt Observations in the Normal Mode Frequency Band at the Geodynamic Observatory Cueva de los Verdes,Lanzarote

We have conducted observations with the aid of a seismo-tiltmeter station, which is based on the Ostrovsky pendulum and installed at the Geodynamic Observatory Cueva de los Verdes at Lanzarote Island since 1995. In this station the signal is separated into two frequency bands – tidal tilts (from 0 to 5 mHz) and ground oscillations in the frequency range of free Earths normal modes (from 0.2 to 5 mHz). The later band, called accelerometer channel, has additional amplification. We analyzed the background records in the frequency range of Earths free oscillations from August 2000 to September 2001, as well as, Earths normal modes after strong earthquakes. We found several distinctive persistent peaks in the spectra of background oscillations. Both amplitudes of distinguished peaks and noises have seasonal variations. We found that spectra of background oscillations are different in the frequency interval between 1.4 and 2.5 mHz for North- South and East-West components.     

基于自适应BP网络的涌潮波速计算模型

运用BP网络附加动量法和自适应学习速率法，建立神经网络模型，模拟计算涌潮波速。根据部分试验数据对网络进行训练，确定相关参数，建立涌潮波速计算模型，同时利用其余部分试验数据对模型进行检验，模拟结果与试验数据吻合较好，相关程度高，表明神经网络模型用于计算涌潮波速是合适的。     

杭州湾潮波运动的一个三维数值模型

应用坐标变换对杭州湾进行了潮波运动的三维数值计算。计算结果与实测符合良好。     

黄、东海环流的数值研究Ⅱ潮及潮致环流数值模拟

该文中数值模拟了黄、东海陆架区的四大天文潮及其潮致拉格朗日环流。运用“流速分解法”将线性三维分潮波问题化为一个分潮潮位及深度平均流的二维问题和一个流速垂向剖面问题求解。其二维问题的底摩擦系数由三维模式导出 ,所导得的线性底摩擦力公式更符合物理意义 ,且避免一般二维模式中底摩擦力的经验假定。结果表明 ,三维模式完全可以通过准二维方法求解 ,以避免一般三维问题的繁重计算     

Estuarine salt conservation: a Lagrangian approach

Understanding tidal and mean flow transport mechanisms that maintain the estuarine salt balance against seaward transport by river flow is one of the fundamental questions of estuarine oceanography. Previous salt transport studies have failed to resolve this problem for two principal methodological reasons, in addition to the inherent variability of estuaries. First, salt transport expansions used to represent the salt balance have included a large number of terms that could not be related to any theory of estuarine circulation and whose physical meaning was thus unclear. Second, it has proven difficult to measure small mean velocities in the presence of much larger tidal variations. A new analysis method that expresses Lagrangian scalar property transport in terms of time and space variations of Eulerian variables is much simpler than expansions previously used and yields new insights into estuarine transport processes. This approach (like previous expansions) is valid for narrow systems in which cross-channel transport processes are weak and the ratio of tidal amplitude to mean depth is small. A surface boundary condition is used to eliminate one class of troublesome terms. The equivalence of the tidal-cycle average transport of tidal variations in salinity and the Stokes transport of mean salinity is then employed to show that the vertically integrated tidal flow plays no role in the overall salt balance. That is, seaward transport of salt caused by the river flow can only be balanced by landward transport resulting from correlations between shear and stratification in the mean, tidal and overtide flows. In a hypothetical inviscid estuary, tide and overtide flows would be vertically uniform, and outward fluvial salt transport could only be balanced by shear and stratification in the mean gravitational circulation. In a more realistic example with strong friction, the gravitational circulation would be severely damped, and inward transport could only be accomplished by correlations of shear and stratification in the tide and overtide flows.     

Study on the Log-Linear Velocity Profile of Near-Bed Tidal Current in Estuarine and Coastal Waters

Many observed data show that the near-bed tidal velocity profile deviates from the usual logarithmic law. The amount of deviation may not be large, but it results in large errors when the logarithmic velocity profile is used to calculate the bed roughness height and friction velocity （or shear stress）. Based on their investigation, Kuo et al. （1996） indicate that the deviation amplitude may exceed 100%. On the basis of fluid dynamic principle, the profile of the near-bed tidal velocity in estuarine and coastal waters is established by introducing Prandtl＇ s mixing length theory and Von Kannan selfsimilarity theory. By the fitting and calculation of the near-bed velocity profde data observed in the west Solent, England, the results are compared with those of the usual logarithmic model, and it is shown that the present near-bed tidal velocity profile model has such advantages as higher fitting precision, and better inner consistency between the roughness height and friction velocity. The calculated roughness height and friction velocity are closer to reality. The conclusions are validated that the logarithmic model underestimates the roughness height and friction velocity during tidal acceleration and overestimates them during tidal deceleration.