1999 Vol. 21, No. 6
Display Method:
1999, 21(6): 1-8.
Abstract:
A new nonlinear equation describing mesoscale eddies in the oceanic flow is established. Using the variational principle, the Liapunov stability of the solitary eddies is discussed. It can be found that both cyclonic and anticyclonic solitary eddies are stable. Numerical computations show that the anticyclonic solitary eddies propagate westward due to the β effect. However, when a Gaussian topography (seamount) is located in upstream of an anticyclonic eddy, the solitary topography can make the anticyclonic eddy move southwards, and its path depends on the location of the Gaussian topography. Furthermore, when two anticyclonic eddies interact, the upstream solitary topography can snake them produce weak merging and weak separation. It is found that the localion of the solitary topography affecu the migration and rotation of these two eddies.
A new nonlinear equation describing mesoscale eddies in the oceanic flow is established. Using the variational principle, the Liapunov stability of the solitary eddies is discussed. It can be found that both cyclonic and anticyclonic solitary eddies are stable. Numerical computations show that the anticyclonic solitary eddies propagate westward due to the β effect. However, when a Gaussian topography (seamount) is located in upstream of an anticyclonic eddy, the solitary topography can make the anticyclonic eddy move southwards, and its path depends on the location of the Gaussian topography. Furthermore, when two anticyclonic eddies interact, the upstream solitary topography can snake them produce weak merging and weak separation. It is found that the localion of the solitary topography affecu the migration and rotation of these two eddies.
1999, 21(6): 9-16.
Abstract:
Multi-year variations of temperature and salinity at the 137°E section are analysed systematically. Main results are as follows:(1)In the 100 m layer, an anomalous low temperature occurred in certain areas of the low latitude in certain years, which is relative to the El Niño event. Analyses also show that the existence of the Mindanao eddy is main reason causing the low tempera-ture occurring near area of 6°～8°N at the 137°E section. (2)During El Niño, the range surrounded by 28℃ isotherm in winter is less than its multi-year averaged value. (3)The subsurface high-salinity water in winter can be classified into four types:strong, substroug, middle and weak.
Multi-year variations of temperature and salinity at the 137°E section are analysed systematically. Main results are as follows:(1)In the 100 m layer, an anomalous low temperature occurred in certain areas of the low latitude in certain years, which is relative to the El Niño event. Analyses also show that the existence of the Mindanao eddy is main reason causing the low tempera-ture occurring near area of 6°～8°N at the 137°E section. (2)During El Niño, the range surrounded by 28℃ isotherm in winter is less than its multi-year averaged value. (3)The subsurface high-salinity water in winter can be classified into four types:strong, substroug, middle and weak.
1999, 21(6): 17-25.
Abstract:
Starting from the equations describing typhoons in the atmosphere the steady three-dimensional stream field and the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct a nonlinear autonomous system in the physical space. It is shown that the centre of typhoon is a local minimum pressure with positive vertical vorticity (cyclonic vorticity) and horizontal convergence in lower levels and a local maximum pressure with negative vertical vorticity (anticy-clonic vorticity) and horizontal divergence in upper levels. Because there exist two saddle-focus points in the autonomous system so there exist the spiral patterns in which the winds blow spirally inside and outside the centre in lower and upper loveis in the Northern Hemisphere and cause the ascending motion near the the rotation of the earth and viscosity of air play an centre. These are in conform fairly well with the observations. It implies that important role in the spiral structure of typhoons.
Starting from the equations describing typhoons in the atmosphere the steady three-dimensional stream field and the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct a nonlinear autonomous system in the physical space. It is shown that the centre of typhoon is a local minimum pressure with positive vertical vorticity (cyclonic vorticity) and horizontal convergence in lower levels and a local maximum pressure with negative vertical vorticity (anticy-clonic vorticity) and horizontal divergence in upper levels. Because there exist two saddle-focus points in the autonomous system so there exist the spiral patterns in which the winds blow spirally inside and outside the centre in lower and upper loveis in the Northern Hemisphere and cause the ascending motion near the the rotation of the earth and viscosity of air play an centre. These are in conform fairly well with the observations. It implies that important role in the spiral structure of typhoons.
1999, 21(6): 26-39.
Abstract:
Interannual variability of the dominated summer climate(rainfall and temperature)patterns over East Asia(China and Japan)and its mechanism are studied. It is found that there is a strong coupling between the large-scale summer rainfall and temperature variations in China on the interannual time-scale. Large-scale above (below) normal rainfall variation generally corresponds to large-scale below(above) normal temperature variation. The long-term variation of the first pattern of singulu value decomposition mainly reflects the increasing(wetting) trend of rainfall and decreasing (cooling) trend of temperature year by year over the middle reach of Chartgjiang River. The component of quasi-biennial oscillation variation is intensified after the middle of 1970s in the coupling variation of rainfall and temperature. It is noticeable that the summer rainfall variation is the exactly biennial oscillation variation in the middle reach of Changjiang River and the Great Bend of Huanghe River after the middle of 1980s. Therefore, there is a trend of time scale shortening in the interannual variation of the summer rainfall in the middle reach of Changjiang River and the Great Bend of Huanghe River. It is found that the large-scale background anomaly in affecting the rainfall and temperature anomalies along the middle and lower reaches of Changjiang River is coherent, that is,the two teleconnection pattetns:the Pacific-Japan(PJ) and Eurasia teleconnection patterns. The rainfall and temperature anomalies along the middle and lower reaches of Changjiang River,connected with the plum rain anomaly in East Asia in summer, is the result of the interaction between the cold and dry air from the temperate and high latitudes and the warm and moist air from the low latitudes. The interannual variations of sea surface temperature anomaly and the connected convective activity in the tropical western Pacific affect significantly the interannual variations of the summer rainfall and temperature in East Asia through the PI teleconnection pattern. There is obvious seasonality of the interaction between the convective activity over the western Pacific and the teleconnection patterns of the general circulation in the Northern Hemisphere (NH).The PJ pattern is not only the most important pattern in the coupled interaction between the interannual variabilities of the convection over the western Pacific and the extratropical general circulation in the NH summer, but also the dominant pattern in the variations for themselves. Through the principal oscillation pattern analysis of the 500 hPa geopotential height in the NH summer of 1984,it is indicated that the energy can propagate from the tropical western Pacific to the northern part of East Asia through the PJ-like oscillation. The impact from the low latitudes can reach 70°N. At the same time,there is also the propagation of energy from the high latitudes to the low latitudes, that is, from the North Pole to 70°N. The impacts from the low latitudes and from the high latitudes are converged around 70°N.
Interannual variability of the dominated summer climate(rainfall and temperature)patterns over East Asia(China and Japan)and its mechanism are studied. It is found that there is a strong coupling between the large-scale summer rainfall and temperature variations in China on the interannual time-scale. Large-scale above (below) normal rainfall variation generally corresponds to large-scale below(above) normal temperature variation. The long-term variation of the first pattern of singulu value decomposition mainly reflects the increasing(wetting) trend of rainfall and decreasing (cooling) trend of temperature year by year over the middle reach of Chartgjiang River. The component of quasi-biennial oscillation variation is intensified after the middle of 1970s in the coupling variation of rainfall and temperature. It is noticeable that the summer rainfall variation is the exactly biennial oscillation variation in the middle reach of Changjiang River and the Great Bend of Huanghe River after the middle of 1980s. Therefore, there is a trend of time scale shortening in the interannual variation of the summer rainfall in the middle reach of Changjiang River and the Great Bend of Huanghe River. It is found that the large-scale background anomaly in affecting the rainfall and temperature anomalies along the middle and lower reaches of Changjiang River is coherent, that is,the two teleconnection pattetns:the Pacific-Japan(PJ) and Eurasia teleconnection patterns. The rainfall and temperature anomalies along the middle and lower reaches of Changjiang River,connected with the plum rain anomaly in East Asia in summer, is the result of the interaction between the cold and dry air from the temperate and high latitudes and the warm and moist air from the low latitudes. The interannual variations of sea surface temperature anomaly and the connected convective activity in the tropical western Pacific affect significantly the interannual variations of the summer rainfall and temperature in East Asia through the PI teleconnection pattern. There is obvious seasonality of the interaction between the convective activity over the western Pacific and the teleconnection patterns of the general circulation in the Northern Hemisphere (NH).The PJ pattern is not only the most important pattern in the coupled interaction between the interannual variabilities of the convection over the western Pacific and the extratropical general circulation in the NH summer, but also the dominant pattern in the variations for themselves. Through the principal oscillation pattern analysis of the 500 hPa geopotential height in the NH summer of 1984,it is indicated that the energy can propagate from the tropical western Pacific to the northern part of East Asia through the PJ-like oscillation. The impact from the low latitudes can reach 70°N. At the same time,there is also the propagation of energy from the high latitudes to the low latitudes, that is, from the North Pole to 70°N. The impacts from the low latitudes and from the high latitudes are converged around 70°N.
1999, 21(6): 40-46.
Abstract:
The spatial and temporal distributions of new production vary largely in different sea areas. To understand the level of new production in the study sea area better, an estimate of new production must be obtained in large spatial and temporal scales. The disequilibrium of 234Th-238U is an effective method for studying new production. Two sampling projects, i. e.,vertically integrated sampling approach(based on trapezoidal integration) and discrete layer sampling approach, are compared in the Xiamen Bay and the northern South China Sea. The coincident results from the two sampling approaches suggest that the vertically integrated sampling approach is not only effective and reliable, but also significantly reduces the number and volume of samples. It is allowed to estimate new production by 234Th-238U disequilibria in large spatial scale.
The spatial and temporal distributions of new production vary largely in different sea areas. To understand the level of new production in the study sea area better, an estimate of new production must be obtained in large spatial and temporal scales. The disequilibrium of 234Th-238U is an effective method for studying new production. Two sampling projects, i. e.,vertically integrated sampling approach(based on trapezoidal integration) and discrete layer sampling approach, are compared in the Xiamen Bay and the northern South China Sea. The coincident results from the two sampling approaches suggest that the vertically integrated sampling approach is not only effective and reliable, but also significantly reduces the number and volume of samples. It is allowed to estimate new production by 234Th-238U disequilibria in large spatial scale.
1999, 21(6): 47-54.
Abstract:
The geotechnical data obtained from the investigation of marine polymetellic nodules in 1994 are used, and are combiped with the data concerned to make synthetic analyses. The type of marine sediment, geotechnical properties and soil strength, etc. are discussed. They will provide basis for design and manufacture of engineering facilities and the equipment to mine the polymetallic nodules used in ocean bed in the future.
The geotechnical data obtained from the investigation of marine polymetellic nodules in 1994 are used, and are combiped with the data concerned to make synthetic analyses. The type of marine sediment, geotechnical properties and soil strength, etc. are discussed. They will provide basis for design and manufacture of engineering facilities and the equipment to mine the polymetallic nodules used in ocean bed in the future.
1999, 21(6): 55-63.
Abstract:
Fault structures of basement in the study area develop well. The large basement faults in EW, NEE and NE direcdons construct and control the principle frame of the regional geological structure on a grand scale. The faults in NS, NNW and NW directions are mostly tensile translational faults, which strongly cut apart, destroy and break the principle structure, form and control secondary differential regional tectonic movement and magmatism characteristics. The burial depth of magnetic basement in the edge rise zone of the East China Sea shelf is ordinarily 3-4 km. The basement comprises Pre-Miocene metamorphic rock and series of igneous rocks formed in different epoches. The crust belongs to continental crust, whose thickness is 24-28 km. The burial depth of magnetic basement in the southern Okinawa Trough basin is ordinarily 5-7 km. The basin can be divided into 4 secondary basins. The basement may mostly comprise basalt or part-metamorphic rock formed by trough tensile movement since Pre-Miocene, which may include old Pre-Tertiary stratigraphy close to continental slope foot. The crust belongs to suboceanic:rust, whose thickness is 15-20 km.
Fault structures of basement in the study area develop well. The large basement faults in EW, NEE and NE direcdons construct and control the principle frame of the regional geological structure on a grand scale. The faults in NS, NNW and NW directions are mostly tensile translational faults, which strongly cut apart, destroy and break the principle structure, form and control secondary differential regional tectonic movement and magmatism characteristics. The burial depth of magnetic basement in the edge rise zone of the East China Sea shelf is ordinarily 3-4 km. The basement comprises Pre-Miocene metamorphic rock and series of igneous rocks formed in different epoches. The crust belongs to continental crust, whose thickness is 24-28 km. The burial depth of magnetic basement in the southern Okinawa Trough basin is ordinarily 5-7 km. The basin can be divided into 4 secondary basins. The basement may mostly comprise basalt or part-metamorphic rock formed by trough tensile movement since Pre-Miocene, which may include old Pre-Tertiary stratigraphy close to continental slope foot. The crust belongs to suboceanic:rust, whose thickness is 15-20 km.
1999, 21(6): 64-71.
Abstract:
According to more than 2 100 drilling hole data, the lithofacies analysis, 14C dating of the sediments, and the field investigation, etc. the distribution regularities, buried situation and sedimentary characteristics of the shaVow buried paleochannel zones on the south coast plain of Laizhou Bay,and their stage division and their relations with sea(salt)-water intrusion have been studied. The shaVow buried paleochannel zones within a buried depth of 60 m on the plain can be divided into the Mihe River, the Weihe River and the Bailang River system. The shallow buried paleochannel zones appear in palm-like and radial山stribution, and coincide respectively with their river's alluvial diluvial fans.On the plain within a buried depth of 60 m, there are 4 stages of paleochannels which have developed since the late period of Late Pleistocene, in which the paleochannel sand strata of the early Wüirm glaciation and the principal Wüirm glaciation,with coarse granularity, well continuity and wide distribution, are both rich in fresh groundwater and the main passage ways of sea (salt)-water intrusion. It is the inportant measures of managing salt-water intrusion to control cxcessive extraction of fresh groundwater in the shallow-buried paleochannel zones and to recharge the groundwater using the pale ochannel zones in the rainy seasons.
According to more than 2 100 drilling hole data, the lithofacies analysis, 14C dating of the sediments, and the field investigation, etc. the distribution regularities, buried situation and sedimentary characteristics of the shaVow buried paleochannel zones on the south coast plain of Laizhou Bay,and their stage division and their relations with sea(salt)-water intrusion have been studied. The shaVow buried paleochannel zones within a buried depth of 60 m on the plain can be divided into the Mihe River, the Weihe River and the Bailang River system. The shallow buried paleochannel zones appear in palm-like and radial山stribution, and coincide respectively with their river's alluvial diluvial fans.On the plain within a buried depth of 60 m, there are 4 stages of paleochannels which have developed since the late period of Late Pleistocene, in which the paleochannel sand strata of the early Wüirm glaciation and the principal Wüirm glaciation,with coarse granularity, well continuity and wide distribution, are both rich in fresh groundwater and the main passage ways of sea (salt)-water intrusion. It is the inportant measures of managing salt-water intrusion to control cxcessive extraction of fresh groundwater in the shallow-buried paleochannel zones and to recharge the groundwater using the pale ochannel zones in the rainy seasons.
1999, 21(6): 72-80.
Abstract:
The paper is the succession of the study on abundance distribution of planktonic copepods in the waters north of Taiwan Island, and the constructions and features of copepod community and the relationships with water environment are analyzed and discussed. The results show that totals of 237 species are identified and the construction of community is complex. The percentage of annual present species is only 32%.The mean values of diversity and evenness of the copepod community are 3.714 and 0.690 respectively, and their horizontal distribution patterns are higher in outshore area than in nearshore area. The copepods of the area can be divided into five ecotypes. The warm-water outshore high-temperature and lower-saline group and tropic oceanic high-temperature and high-saline group can indicate the seasonal changes of the Taiwan Strait water and the Kuroshio surface water respectively. According to the various aspects of calculation and analysis, winter is different from other three seasons in environmental conditions. In spring, summer and autumn, Undinula tralgaris is the most dominant species and salinity is the main factor that affects the community feature values. The communities in the three seasons have the subtropic-tropic characteristics in which warm-water outshore species are dominant and tropic oceanic species occupy also certain proportion. And in winter, the dominant species is Euchaeta marina and the temperature is the trtain factor influencing the community feature values. The community has the tropic oceanic chuacteristics in which tropic oceanic species are dominant.
The paper is the succession of the study on abundance distribution of planktonic copepods in the waters north of Taiwan Island, and the constructions and features of copepod community and the relationships with water environment are analyzed and discussed. The results show that totals of 237 species are identified and the construction of community is complex. The percentage of annual present species is only 32%.The mean values of diversity and evenness of the copepod community are 3.714 and 0.690 respectively, and their horizontal distribution patterns are higher in outshore area than in nearshore area. The copepods of the area can be divided into five ecotypes. The warm-water outshore high-temperature and lower-saline group and tropic oceanic high-temperature and high-saline group can indicate the seasonal changes of the Taiwan Strait water and the Kuroshio surface water respectively. According to the various aspects of calculation and analysis, winter is different from other three seasons in environmental conditions. In spring, summer and autumn, Undinula tralgaris is the most dominant species and salinity is the main factor that affects the community feature values. The communities in the three seasons have the subtropic-tropic characteristics in which warm-water outshore species are dominant and tropic oceanic species occupy also certain proportion. And in winter, the dominant species is Euchaeta marina and the temperature is the trtain factor influencing the community feature values. The community has the tropic oceanic chuacteristics in which tropic oceanic species are dominant.
1999, 21(6): 81-86.
Abstract:
The study on nitrogen budget of Penaeus chinensis[I:(0.255±0.038)g; II:(3.522±0.207)g;Ⅱ:(11.132±0.71)g] is conducted at 3 temperature levels (20, 25, 30℃)and size[(0.344±0.028)g] under 5 salinity levels (5, 13, 20, 28, 35) at 25℃.The results shown as follow:(1) the nitrogen consumption rate (1) increased with increasing of temperature and de-crewed with increasing of body weight. The largest consumption rate is 13.88 mg/(g·d) at salinity 13 and the minimum is 11.78 mg/(g·d) at salinity 5, (2) the proportion of ingested nitrogen allocated to growth(G)decreased significantly with increasing of temperature. The nitrogen average growth rates fed polychaete worm are 34.78%,29.59%,18.53 % and ones fed formulated diet. 26.06%,20.48 %,8.47% and (3) the nitrogen budget fed polychaete worm and fed formulated diet are:100I=27.636+ 3.58E+1.66E+67.13 U and 100I=18.346+4.10E+6.07E+71.49 U, respectively, where E is nitrogen of exuviate, F is feces and U is excretion.
The study on nitrogen budget of Penaeus chinensis[I:(0.255±0.038)g; II:(3.522±0.207)g;Ⅱ:(11.132±0.71)g] is conducted at 3 temperature levels (20, 25, 30℃)and size[(0.344±0.028)g] under 5 salinity levels (5, 13, 20, 28, 35) at 25℃.The results shown as follow:(1) the nitrogen consumption rate (1) increased with increasing of temperature and de-crewed with increasing of body weight. The largest consumption rate is 13.88 mg/(g·d) at salinity 13 and the minimum is 11.78 mg/(g·d) at salinity 5, (2) the proportion of ingested nitrogen allocated to growth(G)decreased significantly with increasing of temperature. The nitrogen average growth rates fed polychaete worm are 34.78%,29.59%,18.53 % and ones fed formulated diet. 26.06%,20.48 %,8.47% and (3) the nitrogen budget fed polychaete worm and fed formulated diet are:100I=27.636+ 3.58E+1.66E+67.13 U and 100I=18.346+4.10E+6.07E+71.49 U, respectively, where E is nitrogen of exuviate, F is feces and U is excretion.
1999, 21(6): 87-93.
Abstract:
A three-step finite element method (FEM) and a large eddy simulation (LES) are applied to incompressible turbulent flow around a seabed pipeline in relative high Reynolds number. Both two-dimensional and three-dimensional numerical simulations are carried out to determine the three-dimensional effect. The results of numerical simulation agree quite well with the wave forces acting on pipeline model measured in physical model test.
A three-step finite element method (FEM) and a large eddy simulation (LES) are applied to incompressible turbulent flow around a seabed pipeline in relative high Reynolds number. Both two-dimensional and three-dimensional numerical simulations are carried out to determine the three-dimensional effect. The results of numerical simulation agree quite well with the wave forces acting on pipeline model measured in physical model test.
1999, 21(6): 94-101.
Abstract:
A finite element analysis method is applied to the dynamic simulation of the seepage field of suction penetration of bucket foundation platform. A numerical method to calculate the penetrating resistance of bucket foundation is suggested. The formule to calculate penetrating resistance of bucket foundation is meliorated and the range of related factors is also suggested. The resalt indicates that the method suggested is appropriate and practicable for engineering practice.
A finite element analysis method is applied to the dynamic simulation of the seepage field of suction penetration of bucket foundation platform. A numerical method to calculate the penetrating resistance of bucket foundation is suggested. The formule to calculate penetrating resistance of bucket foundation is meliorated and the range of related factors is also suggested. The resalt indicates that the method suggested is appropriate and practicable for engineering practice.
1999, 21(6): 102-109.
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1999, 21(6): 110-115.
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1999, 21(6): 116-123.
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1999, 21(6): 124-129.
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1999, 21(6): 130-133.
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1999, 21(6): 134-137.
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1999, 21(6): 138-144.
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