By means of three dimensional POM model,which computes the eddy viscosity coefficient based on two order turbulent closed model,the tide and tidal current in the Beibu Gulf are simulated with fine grid.In the comput...By means of three dimensional POM model,which computes the eddy viscosity coefficient based on two order turbulent closed model,the tide and tidal current in the Beibu Gulf are simulated with fine grid.In the computed region,six islands are considered and the bottom friction coefficients are taken to be various values from the difference of sea region.Acquired tidal harmonic constants are compared with that of 81 tidal observatories.The absolute mean error of K 1 constituent amplitude is 4 6 cm and of the lag is 9°.The absolute mean error of O 1 constituent amplitude is 5 6 cm and of the lag is 7°.The absolute mean error of M 2 constituent amplitude is 6 2 cm and of the lag is 15°.The tide,tidal current,residual water level and tide induced residual current,as well as the vertial distribution of horizontal velocity in this sea region are analysed by the simulated results.展开更多
This paper have collected the measured tides and certain tidal current data in different stages of many projects during past three to five years near the Aojiang River. The harmonic method is used to analyze tide and ...This paper have collected the measured tides and certain tidal current data in different stages of many projects during past three to five years near the Aojiang River. The harmonic method is used to analyze tide and tidal current data observed at five stations in the sea adjacent to Aojiang River. The results show that the tide is mainly regular and semidiumal in the sea near Aojiang of Wenzhou. The tidal amplitudes of M2 constituent are between 170 cm - 193 cm and the lags are between 260~ - 280~, According to the comparison of analytical results of harmonic constants of these stations in 2007, 2010 and 2011, the maximum change of tidal amplitudes and phase-lag range for the main semidiurnal tides （M2, $2, N2）, the diurnal tide （K1, O1） and the shallow water tide （M4, MS4, M6） are 1.8 cm - 4.4 cm and 3~ - 7~, respectively. After analyzing the tide and tidal current characteristics of Aojiang River, this paper uses an unstructured grid and Finite-Volume Coastal Ocean Model （FVCOM） to test the results of simulation. The simulated results agree well with the measured data. The new shoreline and depth which are produced by the construction projects closed in important major years, and the tide and tidal current field for the new shoreline and depth are constructed, which describe the superimposed influences of construction engineering in Aojiang estuary.展开更多
Based on the third-generation oceanic wave prediction model (WAVEWATCH (.) III) the third-generation nearshore wave calculation model (SWAN) and the mathematical tide, tidal current and cyclone current model, which ha...Based on the third-generation oceanic wave prediction model (WAVEWATCH (.) III) the third-generation nearshore wave calculation model (SWAN) and the mathematical tide, tidal current and cyclone current model, which have been improved, interconnected and expanded, a coupled model of offshore wave, tide and sea current under tropical cyclone surges in the South China Sea has been established. The coupled model is driven by the tropical cyclone field containing the background wind field. In order to test the hindcasting effect of the mathematical model, a comparison has been made between the calculated results and the observational results of waves of 15 cyclone cases, water levels and current velocities of the of 7 cyclones. The results of verification indicate that the calculated and observed results are basically identical.展开更多
The spatial-temporal characteristics of internal tides （ITs） in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis sho...The spatial-temporal characteristics of internal tides （ITs） in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis show that the ITs in diurnal and semidiurnal frequencies are prominent at the mooring site, especially for the clockwise rotary component. The diurnal ITs are mostly dominated by the first mode except for that in spring when the second mode is relatively predominant. The semidiurnal ITs display a variable multimodal structure. Moreover, an apparent difference is detected in the kinetic energy of diurnal ITs. The energy is strongest in winter, and followed by that in summer, whereas the value is smallest in spring and autumn. It is suggested that the incoherent motions are responsible for the significant seasonal variations of diurnal ITs, reflecting interaction between diurnal ITs and the varying background conditions. However, the semidiumal ITs are independent of seasonal change, whose energy is smaller and only one-third of the diurnal energy in winter. Nevertheless, the abnormal variations of semidiurnal ITs are also related to the variable background conditions. The incoherent semidiurnal constituent accounts for about 37% of the total semidiurnal tidal kinetic energy, but the diurnal tidal motions contain fewer incoherent component （22.2%）.展开更多
In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tid...In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.展开更多
The tidal current is generally predominant in China's offshore areas. The vertical structure of the observedtidal current is quite complicated with the presence of seasonal thermocline. The observed tidal current ...The tidal current is generally predominant in China's offshore areas. The vertical structure of the observedtidal current is quite complicated with the presence of seasonal thermocline. The observed tidal current may be divided into two parts, an averaged barotropic tide current and a variation tide current. A method for studying the vertical structure of tidal current is developed from the constitution and distribution of energy, and the vertical structure of the observed tide current in the North Huanghai Sea is studied on the basis of the method. The result shows that the reason why the energy of the tidal current is concentrated on the neighbourhood of the thermocline mainly lies in the internal tides i under certain conditions, the fact that the direction of the internal tide current above the thermocline is opposite to the one below the thermocline will be able to cause the rotary directions of the observed tidal current above and below the thermocline to be in opposite. The interaction between the averaged barotropic and the variation tide current plays an important role in forming the vertical structure of the tidal current, and it is mainly the interaction that results in the inho-mogeneous distribution of the tide current energy in the entire water column ; the ratio between the total energies of the internal tide current above the thermocline and the variation tide current in the entire water column is greater than the ratio between the total energies of that below the thermocline and the variation's. In a strong internal tide area such as the neighbourhood of Station L4, at diurnal tide frequency, the above-mentioned corresponding ratios are about 38. 82% and 29. 88%, respectively, and the energy of the internal tide current is about 68. 70%of the energy of the variation tide current; at semidiurnal tide frequency, the above-mentioned corresponding ratios are about 26. 61 % and 19. 73% , respectively, and the total internal tide current energy is about 46. 36% of the total variation tide current energy.展开更多
The Bohai Sea is a shallow semi-enclosed inner sea with an average depth of 18 m and is located at the west of the northern Yellow Sea. The climatological circulation pattern in summer of the Bohai Sea is studied by u...The Bohai Sea is a shallow semi-enclosed inner sea with an average depth of 18 m and is located at the west of the northern Yellow Sea. The climatological circulation pattern in summer of the Bohai Sea is studied by using a wave-tide-circulation coupled model. The simulated temperature and the circulation agree with the observation well. The result shows that the circulation pattern of the Bohai Sea is jointly influenced by the tidal residual current, wind and baroclinic current. There exists an obvious density current along the temperature front from the west part of the Liaodong Bay to the offshore area of the Huanghe Estuary. In the Liaodong Bay there exists a clockwise gyre in the area north to the 40°N. While in the area south to the 40°N the circulation shows a two-gyre structure, the flow from the offshore area of the Huanghe Estuary to the Liaodong Bay splits into two branches in the area between 39°N and 40°N. The west branch turns into north-west and forms an anti-clockwise gyre with the south-westward density current off the west of the Liaodong Bay. The east branch turns to the east and forms a clockwise gyre with the flow along the east coast of the Liaodong Bay. The forming mechanism of the circulation is also discussed in this paper.展开更多
The available data on tidal currents spanning periods greater than six months for the continental shelf of the East China Sea (26°30.052′N, 122°35.998′E) were analyzed using several methods. Tidal Current ...The available data on tidal currents spanning periods greater than six months for the continental shelf of the East China Sea (26°30.052′N, 122°35.998′E) were analyzed using several methods. Tidal Current Harmonic Analysis results demonstrated that semi-diurnal tides dominated the current movement. The tidal currents of the principal diurnal and semidiurnal rotated clockwise with depth, with the deflection of the major semi-axes to the right in the upper layer and to the left in the lower layer. The vertical structures of two principal semi-diurnal constituents-M2 and S2-were similar, which indicates that the tidal currents are mainly barotropic in this area. The main features of the variation of the four principal tidal constituents with depth demonstrate that the currents in this region are influenced by the upper and lower boundary layers. Therefore, the tidal constituents of the shallow water are similar. Different vertical modes were calculated based on the Empirical Orthogonal Function (EOF) analysis of the Eastern and Northern components of the tidal currents, with a variance contribution for the zero-order model of at least 90%. The variance contribution of the baroclinic model is minimal, which further reveals a strong barotropic character for the tidal currents of this region.展开更多
In this paper, a new fully-digital high frequency （HF） radar system OSMAR-SD （ocean state measuring and analyzing radar, S-smaller, D-digital） is employed for observation of the tidal current over the Beibu Gulf, ...In this paper, a new fully-digital high frequency （HF） radar system OSMAR-SD （ocean state measuring and analyzing radar, S-smaller, D-digital） is employed for observation of the tidal current over the Beibu Gulf, South China Sea. This system can operate at two frequencies to achieve wider range and better resolution of measurement. Experimental results show that the radar measurements agree with the tide level data well. The environmental noise level is also analyzed to demonstrate its detrimental effect upon the measurement, the period of this effect is about 24 h. Moreover, it＇s the first time that the characteristic of the irregular diurnal tide over Beibu Gulf is clearly measured by HF radar.展开更多
The Changjiang River Delta is a delta of tremendous scale which is formed under the control of tide and tidal currents. The study on the role of tide and tidal currents in the process of formation and development of t...The Changjiang River Delta is a delta of tremendous scale which is formed under the control of tide and tidal currents. The study on the role of tide and tidal currents in the process of formation and development of the Changjiang River Delta can provide a typical example for the ocean-continent interaction process in the east area of our country. The tide and tidal currents in the Bohai Sea, Yellow Sea and East China Sea at the post-glacial transgression maximum are simulated, the sediment transport field in the Paleo-Changjiang River Estuary(PCRE) and its peripheral area at that time is calculated, and the seabed erosion/accretion pattern is obtained according to the divergence of sediment transport rate. The results show that a distinctive wave belly of standing tidal wave existed at the post-glacial transgression maximum and the wave belly lines protruded seawards from the wave belly point in the mouth of the PCRE. Under the wave belly control tidal currents converge to or diverge from the wave展开更多
The effects of tidal currents(i.e., barotropic and internal tides) are important in the biogeochemistry of a coastal shelf sea. The high-frequency of currents and near-bottom temperatures collected in three consecutiv...The effects of tidal currents(i.e., barotropic and internal tides) are important in the biogeochemistry of a coastal shelf sea. The high-frequency of currents and near-bottom temperatures collected in three consecutive southwest monsoon seasons(May, June, July and August of 2013 until 2015) is presented to reveal the role of the tidal currents to the temperature variability in the coastal shelf sea of the east coast of Peninsular Malaysia(ECPM),south of the South China Sea(SCS). The results of a spectral density and harmonic analysis demonstrate that the near-bottom temperature variability and the tidal currents are influenced by diurnal(O_1 and K_1) and semidiurnal(M_2) tidal currents. The spectral density of residual currents(detided data) at 5, 10 and 16 m depth also shows significant peaks at the diurnal tidal frequency(K_1) and small peaks at the semidiurnal tidal frequency(M_2)indicating the existence of internal tides. The result of the horizontal kinetic energy(HKE) shows a strong intermittent energy of internal tides in the ECPM with the strongest energy is found at 16 m depth during a sporadic cooling event in June and July. A high horizontal cross-shore heat flux(16 m) also indicates strong intrusions of cooler water into the ECPM in June and July. During the short duration of cold pulse water observed in June and July, a cross-wavelet analysis also reveals the strong relationship between the near-bottom temperatures and the internal tidal currents at the diurnal tidal frequency. The intrusion of this cooler water is probably related to the monsoon-induced upwelling in June. It is loosely interpreted that the interaction between the strong barotropic tides and the steep slope in the central basin of the SCS under the stratified condition in southwest monsoon has generated these internal tides. The dissipation of internal tides from the slope area probably has driven the cold-upwelled water into the ECPM coastal shelf sea when the upwelling intensity is the highest in June and July.展开更多
At present there is no theory of sea and oceanic currents due to the lack of understanding of the driving forces. The currents have a vortex character, so only moments of force can set them in motion. In the article, ...At present there is no theory of sea and oceanic currents due to the lack of understanding of the driving forces. The currents have a vortex character, so only moments of force can set them in motion. In the article, it is shown that the gravitation field of the Moon affecting the rotating Earth produces two moments of force: associated and tidal. Although the gravitation field is potential, the rotating Earth is a nonenertial system, in which the moment can occur due to the external potential force. Estimates show that the associated force can be sufficient to produce the observed flow rates. The associated force field tends to increase the natural rotation of the Earth and slow down the speed of the revolution of the Moon around the Earth, i.e. bring the Moon nearer the Earth, its action is opposite to the action of the tidal force. The action of the associated force is examined by the example of the circumpolar and local currents. The associated force produces vortices counterclockwise in the Northern hemisphere and clockwise in the Southern one. The associated force affects the atmosphere resulting in the observed predominance of western winds. It is necessary to take into account the above force when considering such atmospheric phenomena as cyclones and anticyclones, tradewinds, monsoons, etc. In the lithosphere, the associated force makes tectonic plates turn.展开更多
基于有限体积三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)对库克海峡邻近海域的潮汐潮流进行了数值模拟分析,同时搜集了验潮站的潮位数据及其潮汐调和分析数据,对模型结果进行了对比验证。结果表明,库克海峡两...基于有限体积三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)对库克海峡邻近海域的潮汐潮流进行了数值模拟分析,同时搜集了验潮站的潮位数据及其潮汐调和分析数据,对模型结果进行了对比验证。结果表明,库克海峡两侧潮汐存在着显著差异,北侧由新西兰海岸向塔斯曼海的方向上,振幅逐渐降低,南侧由南部宽阔海域向新西兰南部岸线的方向上,振幅逐渐升高,且该区域的潮汐过程受地形和岸线影响较大。库克海峡中部存在典型的往复流,且以向南流动为主。库克海峡南侧存在的隆起地形和海沟是海峡之外该海域潮汐过程的重要影响因子,具体表现在南部海洋中隆起区域的潮流流速显著增加,流向也随之改变。与实测资料的对比结果表明,本研究的数值模拟结果与实测资料基本吻合,能够准确地模拟库克海峡邻近海域的潮汐潮流状况,为相关海洋工程建设以及科学研究等提供了重要的试验依据。展开更多
文摘By means of three dimensional POM model,which computes the eddy viscosity coefficient based on two order turbulent closed model,the tide and tidal current in the Beibu Gulf are simulated with fine grid.In the computed region,six islands are considered and the bottom friction coefficients are taken to be various values from the difference of sea region.Acquired tidal harmonic constants are compared with that of 81 tidal observatories.The absolute mean error of K 1 constituent amplitude is 4 6 cm and of the lag is 9°.The absolute mean error of O 1 constituent amplitude is 5 6 cm and of the lag is 7°.The absolute mean error of M 2 constituent amplitude is 6 2 cm and of the lag is 15°.The tide,tidal current,residual water level and tide induced residual current,as well as the vertial distribution of horizontal velocity in this sea region are analysed by the simulated results.
文摘This paper have collected the measured tides and certain tidal current data in different stages of many projects during past three to five years near the Aojiang River. The harmonic method is used to analyze tide and tidal current data observed at five stations in the sea adjacent to Aojiang River. The results show that the tide is mainly regular and semidiumal in the sea near Aojiang of Wenzhou. The tidal amplitudes of M2 constituent are between 170 cm - 193 cm and the lags are between 260~ - 280~, According to the comparison of analytical results of harmonic constants of these stations in 2007, 2010 and 2011, the maximum change of tidal amplitudes and phase-lag range for the main semidiurnal tides （M2, $2, N2）, the diurnal tide （K1, O1） and the shallow water tide （M4, MS4, M6） are 1.8 cm - 4.4 cm and 3~ - 7~, respectively. After analyzing the tide and tidal current characteristics of Aojiang River, this paper uses an unstructured grid and Finite-Volume Coastal Ocean Model （FVCOM） to test the results of simulation. The simulated results agree well with the measured data. The new shoreline and depth which are produced by the construction projects closed in important major years, and the tide and tidal current field for the new shoreline and depth are constructed, which describe the superimposed influences of construction engineering in Aojiang estuary.
基金This research project was financially supported by the China National Key Basic Research Project(No.2001CB409706).China National Society Commonweal Research Project(No.2001DLA50041),and the Chinese Academy of Sciences Resource and Environment Project(No.
文摘Based on the third-generation oceanic wave prediction model (WAVEWATCH (.) III) the third-generation nearshore wave calculation model (SWAN) and the mathematical tide, tidal current and cyclone current model, which have been improved, interconnected and expanded, a coupled model of offshore wave, tide and sea current under tropical cyclone surges in the South China Sea has been established. The coupled model is driven by the tropical cyclone field containing the background wind field. In order to test the hindcasting effect of the mathematical model, a comparison has been made between the calculated results and the observational results of waves of 15 cyclone cases, water levels and current velocities of the of 7 cyclones. The results of verification indicate that the calculated and observed results are basically identical.
基金The National Natural Science Foundation of China under contract Nos 41276022,U1133001,41230962,41206010 and 41206008the Open Fund of the Key Laboratory of Ocean Circulation and Waves,Chinese Academy of Sciences under contract No.KLOCW1506Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction Technologies,Guangdong Ocean University under contract No.GLOD1401
文摘The spatial-temporal characteristics of internal tides （ITs） in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis show that the ITs in diurnal and semidiurnal frequencies are prominent at the mooring site, especially for the clockwise rotary component. The diurnal ITs are mostly dominated by the first mode except for that in spring when the second mode is relatively predominant. The semidiurnal ITs display a variable multimodal structure. Moreover, an apparent difference is detected in the kinetic energy of diurnal ITs. The energy is strongest in winter, and followed by that in summer, whereas the value is smallest in spring and autumn. It is suggested that the incoherent motions are responsible for the significant seasonal variations of diurnal ITs, reflecting interaction between diurnal ITs and the varying background conditions. However, the semidiumal ITs are independent of seasonal change, whose energy is smaller and only one-third of the diurnal energy in winter. Nevertheless, the abnormal variations of semidiurnal ITs are also related to the variable background conditions. The incoherent semidiurnal constituent accounts for about 37% of the total semidiurnal tidal kinetic energy, but the diurnal tidal motions contain fewer incoherent component （22.2%）.
基金The National Key Fundamental Research and Development Program ("973" Program) of China under contract No. 2010CB429001
文摘In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.
基金The project supported by National Natural science Foundation of China
文摘The tidal current is generally predominant in China's offshore areas. The vertical structure of the observedtidal current is quite complicated with the presence of seasonal thermocline. The observed tidal current may be divided into two parts, an averaged barotropic tide current and a variation tide current. A method for studying the vertical structure of tidal current is developed from the constitution and distribution of energy, and the vertical structure of the observed tide current in the North Huanghai Sea is studied on the basis of the method. The result shows that the reason why the energy of the tidal current is concentrated on the neighbourhood of the thermocline mainly lies in the internal tides i under certain conditions, the fact that the direction of the internal tide current above the thermocline is opposite to the one below the thermocline will be able to cause the rotary directions of the observed tidal current above and below the thermocline to be in opposite. The interaction between the averaged barotropic and the variation tide current plays an important role in forming the vertical structure of the tidal current, and it is mainly the interaction that results in the inho-mogeneous distribution of the tide current energy in the entire water column ; the ratio between the total energies of the internal tide current above the thermocline and the variation tide current in the entire water column is greater than the ratio between the total energies of that below the thermocline and the variation's. In a strong internal tide area such as the neighbourhood of Station L4, at diurnal tide frequency, the above-mentioned corresponding ratios are about 38. 82% and 29. 88%, respectively, and the energy of the internal tide current is about 68. 70%of the energy of the variation tide current; at semidiurnal tide frequency, the above-mentioned corresponding ratios are about 26. 61 % and 19. 73% , respectively, and the total internal tide current energy is about 46. 36% of the total variation tide current energy.
基金The National Key Research and Development Program of China under contract Nos 2017YFA0604101,2016YFB0201103,2017YFA0604104,2016YFC0503602,2016YFC1401403 and 2017YFC1404000the China Ocean Mineral Resources R&D Association program under contract No.DY135-E2-1-06+3 种基金the National Basic Research Program(973 Program)of China under contract No.2014CB745004the Ocean Forecast System project of the China-ASEAN Maritime Coopeartion Fundthe Strategic Priority Research Program of Chinese Academy of Sciences under contract No.XDA11020301the National Natural Science Foundation of China under contract No.41206025
文摘The Bohai Sea is a shallow semi-enclosed inner sea with an average depth of 18 m and is located at the west of the northern Yellow Sea. The climatological circulation pattern in summer of the Bohai Sea is studied by using a wave-tide-circulation coupled model. The simulated temperature and the circulation agree with the observation well. The result shows that the circulation pattern of the Bohai Sea is jointly influenced by the tidal residual current, wind and baroclinic current. There exists an obvious density current along the temperature front from the west part of the Liaodong Bay to the offshore area of the Huanghe Estuary. In the Liaodong Bay there exists a clockwise gyre in the area north to the 40°N. While in the area south to the 40°N the circulation shows a two-gyre structure, the flow from the offshore area of the Huanghe Estuary to the Liaodong Bay splits into two branches in the area between 39°N and 40°N. The west branch turns into north-west and forms an anti-clockwise gyre with the south-westward density current off the west of the Liaodong Bay. The east branch turns to the east and forms a clockwise gyre with the flow along the east coast of the Liaodong Bay. The forming mechanism of the circulation is also discussed in this paper.
基金supported by the National Basic Research Program of China (2007CB411807)the National Natural Science Foundation of China (40806072,41176009)
文摘The available data on tidal currents spanning periods greater than six months for the continental shelf of the East China Sea (26°30.052′N, 122°35.998′E) were analyzed using several methods. Tidal Current Harmonic Analysis results demonstrated that semi-diurnal tides dominated the current movement. The tidal currents of the principal diurnal and semidiurnal rotated clockwise with depth, with the deflection of the major semi-axes to the right in the upper layer and to the left in the lower layer. The vertical structures of two principal semi-diurnal constituents-M2 and S2-were similar, which indicates that the tidal currents are mainly barotropic in this area. The main features of the variation of the four principal tidal constituents with depth demonstrate that the currents in this region are influenced by the upper and lower boundary layers. Therefore, the tidal constituents of the shallow water are similar. Different vertical modes were calculated based on the Empirical Orthogonal Function (EOF) analysis of the Eastern and Northern components of the tidal currents, with a variance contribution for the zero-order model of at least 90%. The variance contribution of the baroclinic model is minimal, which further reveals a strong barotropic character for the tidal currents of this region.
基金Supported by the Ocean Public Welfare Scientific Research Project(201205032-3)the National Key Scientific Instrument and Equipment Development Project(2013YQ160793)
文摘In this paper, a new fully-digital high frequency （HF） radar system OSMAR-SD （ocean state measuring and analyzing radar, S-smaller, D-digital） is employed for observation of the tidal current over the Beibu Gulf, South China Sea. This system can operate at two frequencies to achieve wider range and better resolution of measurement. Experimental results show that the radar measurements agree with the tide level data well. The environmental noise level is also analyzed to demonstrate its detrimental effect upon the measurement, the period of this effect is about 24 h. Moreover, it＇s the first time that the characteristic of the irregular diurnal tide over Beibu Gulf is clearly measured by HF radar.
文摘The Changjiang River Delta is a delta of tremendous scale which is formed under the control of tide and tidal currents. The study on the role of tide and tidal currents in the process of formation and development of the Changjiang River Delta can provide a typical example for the ocean-continent interaction process in the east area of our country. The tide and tidal currents in the Bohai Sea, Yellow Sea and East China Sea at the post-glacial transgression maximum are simulated, the sediment transport field in the Paleo-Changjiang River Estuary(PCRE) and its peripheral area at that time is calculated, and the seabed erosion/accretion pattern is obtained according to the divergence of sediment transport rate. The results show that a distinctive wave belly of standing tidal wave existed at the post-glacial transgression maximum and the wave belly lines protruded seawards from the wave belly point in the mouth of the PCRE. Under the wave belly control tidal currents converge to or diverge from the wave
基金The Higher Institutional Centre of Excellent Universiti Malaysia Terengganu under contract No.TJ66928the Malaysia Coastal Observation Network Project under the Institute of Oceanography and Environment,Universiti Malaysia Terengganu of Malaysia
文摘The effects of tidal currents(i.e., barotropic and internal tides) are important in the biogeochemistry of a coastal shelf sea. The high-frequency of currents and near-bottom temperatures collected in three consecutive southwest monsoon seasons(May, June, July and August of 2013 until 2015) is presented to reveal the role of the tidal currents to the temperature variability in the coastal shelf sea of the east coast of Peninsular Malaysia(ECPM),south of the South China Sea(SCS). The results of a spectral density and harmonic analysis demonstrate that the near-bottom temperature variability and the tidal currents are influenced by diurnal(O_1 and K_1) and semidiurnal(M_2) tidal currents. The spectral density of residual currents(detided data) at 5, 10 and 16 m depth also shows significant peaks at the diurnal tidal frequency(K_1) and small peaks at the semidiurnal tidal frequency(M_2)indicating the existence of internal tides. The result of the horizontal kinetic energy(HKE) shows a strong intermittent energy of internal tides in the ECPM with the strongest energy is found at 16 m depth during a sporadic cooling event in June and July. A high horizontal cross-shore heat flux(16 m) also indicates strong intrusions of cooler water into the ECPM in June and July. During the short duration of cold pulse water observed in June and July, a cross-wavelet analysis also reveals the strong relationship between the near-bottom temperatures and the internal tidal currents at the diurnal tidal frequency. The intrusion of this cooler water is probably related to the monsoon-induced upwelling in June. It is loosely interpreted that the interaction between the strong barotropic tides and the steep slope in the central basin of the SCS under the stratified condition in southwest monsoon has generated these internal tides. The dissipation of internal tides from the slope area probably has driven the cold-upwelled water into the ECPM coastal shelf sea when the upwelling intensity is the highest in June and July.
文摘At present there is no theory of sea and oceanic currents due to the lack of understanding of the driving forces. The currents have a vortex character, so only moments of force can set them in motion. In the article, it is shown that the gravitation field of the Moon affecting the rotating Earth produces two moments of force: associated and tidal. Although the gravitation field is potential, the rotating Earth is a nonenertial system, in which the moment can occur due to the external potential force. Estimates show that the associated force can be sufficient to produce the observed flow rates. The associated force field tends to increase the natural rotation of the Earth and slow down the speed of the revolution of the Moon around the Earth, i.e. bring the Moon nearer the Earth, its action is opposite to the action of the tidal force. The action of the associated force is examined by the example of the circumpolar and local currents. The associated force produces vortices counterclockwise in the Northern hemisphere and clockwise in the Southern one. The associated force affects the atmosphere resulting in the observed predominance of western winds. It is necessary to take into account the above force when considering such atmospheric phenomena as cyclones and anticyclones, tradewinds, monsoons, etc. In the lithosphere, the associated force makes tectonic plates turn.
文摘基于有限体积三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)对库克海峡邻近海域的潮汐潮流进行了数值模拟分析,同时搜集了验潮站的潮位数据及其潮汐调和分析数据,对模型结果进行了对比验证。结果表明,库克海峡两侧潮汐存在着显著差异,北侧由新西兰海岸向塔斯曼海的方向上,振幅逐渐降低,南侧由南部宽阔海域向新西兰南部岸线的方向上,振幅逐渐升高,且该区域的潮汐过程受地形和岸线影响较大。库克海峡中部存在典型的往复流,且以向南流动为主。库克海峡南侧存在的隆起地形和海沟是海峡之外该海域潮汐过程的重要影响因子,具体表现在南部海洋中隆起区域的潮流流速显著增加,流向也随之改变。与实测资料的对比结果表明,本研究的数值模拟结果与实测资料基本吻合,能够准确地模拟库克海峡邻近海域的潮汐潮流状况,为相关海洋工程建设以及科学研究等提供了重要的试验依据。
