Microwave remote sensing is one of the most useful methods for observing the ocean parameters. The Doppler frequency or interferometric phase of the radar echoes can be used for an ocean surface current speed retrieva...Microwave remote sensing is one of the most useful methods for observing the ocean parameters. The Doppler frequency or interferometric phase of the radar echoes can be used for an ocean surface current speed retrieval,which is widely used in spaceborne and airborne radars. While the effect of the ocean currents and waves is interactional. It is impossible to retrieve the ocean surface current speed from Doppler frequency shift directly. In order to study the relationship between the ocean surface current speed and the Doppler frequency shift, a numerical ocean surface Doppler spectrum model is established and validated with a reference. The input parameters of ocean Doppler spectrum include an ocean wave elevation model, a directional distribution function, and wind speed and direction. The suitable ocean wave elevation spectrum and the directional distribution function are selected by comparing the ocean Doppler spectrum in C band with an empirical geophysical model function（CDOP）. What is more, the error sensitivities of ocean surface current speed to the wind speed and direction are analyzed. All these simulations are in Ku band. The simulation results show that the ocean surface current speed error is sensitive to the wind speed and direction errors. With VV polarization, the ocean surface current speed error is about 0.15 m/s when the wind speed error is 2 m/s, and the ocean surface current speed error is smaller than 0.3 m/s when the wind direction error is within 20° in the cross wind direction.展开更多
A three-dimensional baroclinic numerical forecasting model for anomaly current field is developed forapplication in the Bohai Sea and the upper layer of the Huanghai Sea and the East China Sea. All the dynamical varia...A three-dimensional baroclinic numerical forecasting model for anomaly current field is developed forapplication in the Bohai Sea and the upper layer of the Huanghai Sea and the East China Sea. All the dynamical variables, including temperature and salinity, can be calculated predictively by using the model. The results of the numerical weather prediction are used as input fields,and various dynamic and thermodynamic boundary conditions areadopted. So, the model can be used as an operational numerical forecasting model for current fields. In this paper,the structure of the model is presented in detail, various tests for the performance of the model are made, and thedependence of the model on some parameters is discussed. The results of the numerical simulation using historicaldata and experimental forecasting tests are also presented.展开更多
Ocean current forecasting is still in explorative stage of study. In the study, we face some problems that have not been met before. The solving of these problems has become fundamental premise for realizing the ocean...Ocean current forecasting is still in explorative stage of study. In the study, we face some problems that have not been met before. The solving of these problems has become fundamental premise for realizing the ocean current forecasting. In the present paper are discussed in depth the physical essence for such basic problems as the predictability of ocean current, the predictable currents, the dynamical basis for studying respectively the tidal current and circulation, the necessity of boundary model, the models on regions with different scales and their link. The foundations and plans to solve the problems are demonstrated. Finally a set of operational numerical forecasting system for ocean current is proposed.展开更多
A new data insertion approach is applied to the Derber and Rosati ocean data assimilation (ODA) system, a system that uses a variational scheme to analyze ocean temperature and provide ocean model corrections continuo...A new data insertion approach is applied to the Derber and Rosati ocean data assimilation (ODA) system, a system that uses a variational scheme to analyze ocean temperature and provide ocean model corrections continuously. Utilizing the same analysis component as the original system, the new approach conducts analyses to derive model corrections intermittently at once-daily intervals. A technique similar to the Incremental Analysis Update (IAU) method of Bloom et al. is applied to incorporate the corrections into the model gradually and continuously. This approach is computationally more economical than the original.A 13-year global ocean analysis from 1986 to 1998 is produced using this new approach and compared with an analysis based on the original one. An examination of both analyses in the tropical Pacific Ocean shows that they have qualitatively similar annual and interannual temperature variability. However, the new approach produces smoother monthly analyses. Moreover, compared to the independent展开更多
To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is...To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is developed. Numerical computation of the annually cyclic circulation fields is performed. The results of the annual mean zonal currents and deep to abyssal western boundary currents in the equatorial Pacific Ocean are reported. The North Equatorial Current,the North Equatorial Countercurrent, the South Equatorial Current and the Equatorial Undercurrent are fairly well simulated. The model well reproduces the northward flowing abyssal western boundary current.From the model results a lower deep western boundary current east of the Bismarck-Solomon-New Hebrides Island chain at depths around 2 000 m has been found. The model results also show that the currents in the equatorial Pacific Ocean have multi-layer structures both in zonal currents and western boundary currents, indicating that the global ocean overturning thermohaline circulation appears of multi-layer pattern.展开更多
In order to control the lateral motion of a jet trencher which is important for stable trenching operation,the oscillation characteristics of the jet trencher are researched. The jet trencher is simplified into a sing...In order to control the lateral motion of a jet trencher which is important for stable trenching operation,the oscillation characteristics of the jet trencher are researched. The jet trencher is simplified into a single degree of freedom model with restoring and damping force. The nonlinear mathematical model of the trencher laterally oscillating in ocean currents is established,and its approximate analytical solution is obtained.Results show that the analytical solution has small differences with numerical solution based on the fourth-order Runge-Kutta method and can effectively describe the underwater oscillation. A double-loop PID controller is designed to control the lateral motion displacement of the trencher to return to the center of the pipeline route which is effective and robust for the propulsion system.展开更多
A 30-d current numerical simulation is running for the Yangshan Port,the Changjiang Estuary,the Hangzhou Bay and their adjacent seas using a finite volume coastal ocean model （FVCOM）,with Changjiang River runoff and...A 30-d current numerical simulation is running for the Yangshan Port,the Changjiang Estuary,the Hangzhou Bay and their adjacent seas using a finite volume coastal ocean model （FVCOM）,with Changjiang River runoff and wind effect being considered.At the open boundary,this model is driven by the water level obtained from prediction including eight main partial tides.After the harmonic analysis,the cotidal chart and the iso-amplitude line as well as the current ellipse distribution map are displayed to illustrate the propagation property of a tidal wave.Horizontal velocity of both the U and V components coincides with the actual measurement,which shows that the model result is credible to describe the hydrodynamic pattern in this sea area.On this basis,real-time current data from high-frequency radar is assimilated with the implementation of quick ensemble Kalman filter,which takes the variation tendency of the state vector to compute the analysis field,instead of integrating the field for N （the number of ensemble） times as it used to in the standard EnKF,aiming at raising the efficiency of computation,reducing the error of prediction and at the same time,improving the forecast effect.展开更多
In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given a...In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.展开更多
Studies on oceanic conditions in the South China Sea (SCS) and adjacent waters are helpful for thorough understanding of summer monsoons in East Asia. To have a 3-dimensional picture of how the oceanic currents vary, ...Studies on oceanic conditions in the South China Sea (SCS) and adjacent waters are helpful for thorough understanding of summer monsoons in East Asia. To have a 3-dimensional picture of how the oceanic currents vary, the oceanic elements in the South China Sea (SCS) and its neighboring sea regions in January ~ August 1998 have been simulated by using the improved Princeton University Ocean Model (POM) in this paper. The main results are in good agreement with that of ocean investigations and other simulations. The results show that the SCS branch of the Kuroshio Current is an important part in the north SCS from January to August; the SCS warm current is reproduced clearly in all months except in winter; there always exists a large-scale anti-cyclonic vortex on the right of the Kuroshio Current from January to August. In the model domain, the surface currents of the SCS have the closest relations with the monsoon with an apparent seasonal variation. In addition, the developing characteristics of the SST in the SCS and its neighboring sea regions before and after the summer monsoon onset are also well simulated by the improved POM. Those are the foundation for developing a coupled regional ocean-atmospheric model system.展开更多
The new technology of geomorphology visualization modeling and virtual reality for tidal current numerical simulation are the important methods utilized in coastal ocean research. In the project of studying the evolut...The new technology of geomorphology visualization modeling and virtual reality for tidal current numerical simulation are the important methods utilized in coastal ocean research. In the project of studying the evolutionary trend of radial sand ridges in South Yellow Sea of China, this method becomes the key to reveal the correlation betweenthe seabed topography and the hydrodynamic factor——tidal current. It is proved that using the geomorphology visualization and tidal virtual reality techniques, oceanog-raphers might be able to intuitively discover the interaction pattern of sand ridges and tidal current, predicting the development of sand ridge stability in the future. Furthermore,a prototypic software system——VROcean was designed andimplemented to examine the performance of the new visualization technology on the contrast to traditional methods.展开更多
基金The National Natural Science Foundation of China under contract No.41606202the National Key Research and Development Program of China under contract No.2016YFC1401002the Open Fund of Key Laboratory of State Oceanic Administration(SOA) for Space Ocean Remote Sensing and Application under contract No.201601001
文摘Microwave remote sensing is one of the most useful methods for observing the ocean parameters. The Doppler frequency or interferometric phase of the radar echoes can be used for an ocean surface current speed retrieval,which is widely used in spaceborne and airborne radars. While the effect of the ocean currents and waves is interactional. It is impossible to retrieve the ocean surface current speed from Doppler frequency shift directly. In order to study the relationship between the ocean surface current speed and the Doppler frequency shift, a numerical ocean surface Doppler spectrum model is established and validated with a reference. The input parameters of ocean Doppler spectrum include an ocean wave elevation model, a directional distribution function, and wind speed and direction. The suitable ocean wave elevation spectrum and the directional distribution function are selected by comparing the ocean Doppler spectrum in C band with an empirical geophysical model function（CDOP）. What is more, the error sensitivities of ocean surface current speed to the wind speed and direction are analyzed. All these simulations are in Ku band. The simulation results show that the ocean surface current speed error is sensitive to the wind speed and direction errors. With VV polarization, the ocean surface current speed error is about 0.15 m/s when the wind speed error is 2 m/s, and the ocean surface current speed error is smaller than 0.3 m/s when the wind direction error is within 20° in the cross wind direction.
文摘A three-dimensional baroclinic numerical forecasting model for anomaly current field is developed forapplication in the Bohai Sea and the upper layer of the Huanghai Sea and the East China Sea. All the dynamical variables, including temperature and salinity, can be calculated predictively by using the model. The results of the numerical weather prediction are used as input fields,and various dynamic and thermodynamic boundary conditions areadopted. So, the model can be used as an operational numerical forecasting model for current fields. In this paper,the structure of the model is presented in detail, various tests for the performance of the model are made, and thedependence of the model on some parameters is discussed. The results of the numerical simulation using historicaldata and experimental forecasting tests are also presented.
文摘Ocean current forecasting is still in explorative stage of study. In the study, we face some problems that have not been met before. The solving of these problems has become fundamental premise for realizing the ocean current forecasting. In the present paper are discussed in depth the physical essence for such basic problems as the predictability of ocean current, the predictable currents, the dynamical basis for studying respectively the tidal current and circulation, the necessity of boundary model, the models on regions with different scales and their link. The foundations and plans to solve the problems are demonstrated. Finally a set of operational numerical forecasting system for ocean current is proposed.
基金This research was supported bythe National Science Foundation (ATM-9321354) and the National Oceanic and Atmospheric Administration (NA46-GP0217), and computing resources were provided by the National Center for Atmospheric Research Scientific Computin
文摘A new data insertion approach is applied to the Derber and Rosati ocean data assimilation (ODA) system, a system that uses a variational scheme to analyze ocean temperature and provide ocean model corrections continuously. Utilizing the same analysis component as the original system, the new approach conducts analyses to derive model corrections intermittently at once-daily intervals. A technique similar to the Incremental Analysis Update (IAU) method of Bloom et al. is applied to incorporate the corrections into the model gradually and continuously. This approach is computationally more economical than the original.A 13-year global ocean analysis from 1986 to 1998 is produced using this new approach and compared with an analysis based on the original one. An examination of both analyses in the tropical Pacific Ocean shows that they have qualitatively similar annual and interannual temperature variability. However, the new approach produces smoother monthly analyses. Moreover, compared to the independent
基金This study is supported by the National Natural Sci-ence Foundation of China under contract No.40136010the Major State Basic Research Program of China under contract No.G1999043808the Youth Fund of National“863”Project of China under contract No.2002AA639350.
文摘To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is developed. Numerical computation of the annually cyclic circulation fields is performed. The results of the annual mean zonal currents and deep to abyssal western boundary currents in the equatorial Pacific Ocean are reported. The North Equatorial Current,the North Equatorial Countercurrent, the South Equatorial Current and the Equatorial Undercurrent are fairly well simulated. The model well reproduces the northward flowing abyssal western boundary current.From the model results a lower deep western boundary current east of the Bismarck-Solomon-New Hebrides Island chain at depths around 2 000 m has been found. The model results also show that the currents in the equatorial Pacific Ocean have multi-layer structures both in zonal currents and western boundary currents, indicating that the global ocean overturning thermohaline circulation appears of multi-layer pattern.
基金Sponsored by the High Technology Ship Research and Program of Ministry of Industry and Information Technology of the People's Republic of China(Grant No.539[2012])the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120073120014)
文摘In order to control the lateral motion of a jet trencher which is important for stable trenching operation,the oscillation characteristics of the jet trencher are researched. The jet trencher is simplified into a single degree of freedom model with restoring and damping force. The nonlinear mathematical model of the trencher laterally oscillating in ocean currents is established,and its approximate analytical solution is obtained.Results show that the analytical solution has small differences with numerical solution based on the fourth-order Runge-Kutta method and can effectively describe the underwater oscillation. A double-loop PID controller is designed to control the lateral motion displacement of the trencher to return to the center of the pipeline route which is effective and robust for the propulsion system.
基金The Hi-tech Research and Development Program of China (863 Program) under contract No.2007AA09Z117the Public Science and Technology Research Funds Projects of Ocean under contract Nos 200905001 and 201005019
文摘A 30-d current numerical simulation is running for the Yangshan Port,the Changjiang Estuary,the Hangzhou Bay and their adjacent seas using a finite volume coastal ocean model （FVCOM）,with Changjiang River runoff and wind effect being considered.At the open boundary,this model is driven by the water level obtained from prediction including eight main partial tides.After the harmonic analysis,the cotidal chart and the iso-amplitude line as well as the current ellipse distribution map are displayed to illustrate the propagation property of a tidal wave.Horizontal velocity of both the U and V components coincides with the actual measurement,which shows that the model result is credible to describe the hydrodynamic pattern in this sea area.On this basis,real-time current data from high-frequency radar is assimilated with the implementation of quick ensemble Kalman filter,which takes the variation tendency of the state vector to compute the analysis field,instead of integrating the field for N （the number of ensemble） times as it used to in the standard EnKF,aiming at raising the efficiency of computation,reducing the error of prediction and at the same time,improving the forecast effect.
文摘In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.
基金Key project of the Natural Science Foundation of China "an analysis of regional climatic changes in China and study of its mecha
文摘Studies on oceanic conditions in the South China Sea (SCS) and adjacent waters are helpful for thorough understanding of summer monsoons in East Asia. To have a 3-dimensional picture of how the oceanic currents vary, the oceanic elements in the South China Sea (SCS) and its neighboring sea regions in January ~ August 1998 have been simulated by using the improved Princeton University Ocean Model (POM) in this paper. The main results are in good agreement with that of ocean investigations and other simulations. The results show that the SCS branch of the Kuroshio Current is an important part in the north SCS from January to August; the SCS warm current is reproduced clearly in all months except in winter; there always exists a large-scale anti-cyclonic vortex on the right of the Kuroshio Current from January to August. In the model domain, the surface currents of the SCS have the closest relations with the monsoon with an apparent seasonal variation. In addition, the developing characteristics of the SST in the SCS and its neighboring sea regions before and after the summer monsoon onset are also well simulated by the improved POM. Those are the foundation for developing a coupled regional ocean-atmospheric model system.
基金This work was conducted as part of the production of the research projects supported by the National Natural Science Foundation of China (Grant No. 49701013) the Chinese National Institutes of Technology (Grant No. 96-922-03-01).
文摘The new technology of geomorphology visualization modeling and virtual reality for tidal current numerical simulation are the important methods utilized in coastal ocean research. In the project of studying the evolutionary trend of radial sand ridges in South Yellow Sea of China, this method becomes the key to reveal the correlation betweenthe seabed topography and the hydrodynamic factor——tidal current. It is proved that using the geomorphology visualization and tidal virtual reality techniques, oceanog-raphers might be able to intuitively discover the interaction pattern of sand ridges and tidal current, predicting the development of sand ridge stability in the future. Furthermore,a prototypic software system——VROcean was designed andimplemented to examine the performance of the new visualization technology on the contrast to traditional methods.
文摘大洋环流的强度变化,对区域乃至全球气候有重要影响。综述了在过去50年中,海洋模式的发展。经过了几代人的开发,国内外全球大洋环流模式、近海和区域环流模式都有了很大改进,能较好地模拟大洋海面温度和高度的分布、海流分布以及E lN ino和La N ina的演变过程等。但是,由于观测资料的短缺,数值模式开发还不够完善,海洋边界流的模拟仍不够好。有些探索是基于压力坐标的、非Boussinesq近似的海洋环流模式;将海洋模式的开边界以余流和潮流合成给出,能保证整个计算区域内水量进出的平衡;摒弃刚盖模型,用自由表面模型取而代之,以及借助海洋资料同化系统,开发海气耦合模式,都是海洋环流模式的发展方向。众多研究认为,不断改进和完善动力框架和各种差分格式的设计将有助于提高海洋环流模式的模拟能力。
