2003 Vol. 25, No. 5
Display Method:
2003, 25(5): 1-8.
Abstract:
The wavelet transformation methods were applied to 8 a(1993~2000)TOPEX/Poseidon data set to investigate the multiple time-scale variability of sea surface height(SSH)in the northeastern South China Sea(SCS). Analysis results indicate that SSH variation mainly subjects to influences from three factors of different time-scale. Among them,the seasonal variation(Va),with period range from 0.60 to 1.20 a,appears to be the strongest, which mainly relates to seasonal cycling of SSH.Secondly,the variation(V25),with period range from 0.17 to 0.45 a(i.e.,of 2~5 months period),mainly relates to SSH variation caused by mesoscale phenomena.Arelatively weak factor is the interannual variation(Vi)with period range from 1.50 to 5.00 a,w hich mainly associates with SSH changes of El Niño events.Analyses also show that,from eight years mean distribution,high variation areas of energy variance V25 appears mainly to the west of Luzon Strait with energy maximums in 1995,1996 and 1999.Areas of high Va appear in the sea area northwest off Luzon Island show a energy peak in 1995.And high variation areas of inter annual variance Vi are located to southwest of Taiwan Island which reaches energy maximum during the 1997/1998 El Niño event period.
The wavelet transformation methods were applied to 8 a(1993~2000)TOPEX/Poseidon data set to investigate the multiple time-scale variability of sea surface height(SSH)in the northeastern South China Sea(SCS). Analysis results indicate that SSH variation mainly subjects to influences from three factors of different time-scale. Among them,the seasonal variation(Va),with period range from 0.60 to 1.20 a,appears to be the strongest, which mainly relates to seasonal cycling of SSH.Secondly,the variation(V25),with period range from 0.17 to 0.45 a(i.e.,of 2~5 months period),mainly relates to SSH variation caused by mesoscale phenomena.Arelatively weak factor is the interannual variation(Vi)with period range from 1.50 to 5.00 a,w hich mainly associates with SSH changes of El Niño events.Analyses also show that,from eight years mean distribution,high variation areas of energy variance V25 appears mainly to the west of Luzon Strait with energy maximums in 1995,1996 and 1999.Areas of high Va appear in the sea area northwest off Luzon Island show a energy peak in 1995.And high variation areas of inter annual variance Vi are located to southwest of Taiwan Island which reaches energy maximum during the 1997/1998 El Niño event period.
2003, 25(5): 9-20.
Abstract:
By means of three-dimensional baroclinic primitive equation model——Hamburg shelf ocean model (HAMSOM),the tide and tidal currents in the seas adjacent to Zhejiang are simulated.Furthermore,the original model is improved by two numerical technologies——nested grid and moving boundary method,which are introduced to increase the computational precision.The improved mode is proved to be successful while it is applied to the seas adjacent to Zhejiang.Comparing the computed values with those of 50 tidal observatories,it is found that the computational precision with fine grids and moving boundary is generally higher than that with coarse grids or fixed boundary.The root-mean-square values of comparative results show that the difference between the simulated and the observed amplitudes of M2 constituent is only 4.6 cm,the difference of phase-lags is 7.14°;the difference of amplitudes and phase-lags of S2 constituent are 5.0 cm and 5.4°;the difference of amplitudes and phas-elags of K1 constituent are 2.25 cm and 5.76°;the difference of amplitudes and phase-lags of O1 constituent are 1.56 cm and 5.5°.
By means of three-dimensional baroclinic primitive equation model——Hamburg shelf ocean model (HAMSOM),the tide and tidal currents in the seas adjacent to Zhejiang are simulated.Furthermore,the original model is improved by two numerical technologies——nested grid and moving boundary method,which are introduced to increase the computational precision.The improved mode is proved to be successful while it is applied to the seas adjacent to Zhejiang.Comparing the computed values with those of 50 tidal observatories,it is found that the computational precision with fine grids and moving boundary is generally higher than that with coarse grids or fixed boundary.The root-mean-square values of comparative results show that the difference between the simulated and the observed amplitudes of M2 constituent is only 4.6 cm,the difference of phase-lags is 7.14°;the difference of amplitudes and phase-lags of S2 constituent are 5.0 cm and 5.4°;the difference of amplitudes and phas-elags of K1 constituent are 2.25 cm and 5.76°;the difference of amplitudes and phase-lags of O1 constituent are 1.56 cm and 5.5°.
2003, 25(5): 21-28.
Abstract:
Combining the NCEP re-analysis wind data with an empirical typhoon wind model,the wind fields are formed and compared with the TOPEX/Poseidon altimetric wind speeds,there is generally consistency between them.The wind fields are used to drive a third-generation wind wave model to simulate the wave fields in the South China Sea during the period of Typhoon York in 1999.The significant wave heights from the wave model are under estimated while compared with the TOPEX/Poseidon altimetric data.Then,a simple optimal interpo lation assimilation technology is employed in the wave model,the result shows that the performance of the wave model is improved and its impact of assimilation is obvious especially in the swell part.The lasting time of the assimilation is about 43 h.
Combining the NCEP re-analysis wind data with an empirical typhoon wind model,the wind fields are formed and compared with the TOPEX/Poseidon altimetric wind speeds,there is generally consistency between them.The wind fields are used to drive a third-generation wind wave model to simulate the wave fields in the South China Sea during the period of Typhoon York in 1999.The significant wave heights from the wave model are under estimated while compared with the TOPEX/Poseidon altimetric data.Then,a simple optimal interpo lation assimilation technology is employed in the wave model,the result shows that the performance of the wave model is improved and its impact of assimilation is obvious especially in the swell part.The lasting time of the assimilation is about 43 h.
2003, 25(5): 29-37.
Abstract:
In general,El Niño refers to the appearance of unusual high sea surface temperature in the eastern tropical Pacific Ocean.But in recent El Niño events(for example,1982/1983 and 1986/1987),the warm sea surface temperature anomaly first appears in the western Pacific Ocean and then expands eastward.That is to say,the El Niño events are not only confined to the eastern tropical Pacific Ocean.Based on the above facts,a baroclinic two layers ocean model is developed and used to study the responding characteristics of equatorial eastern and western Pacific Ocean to relaxation of trade winds.The results show the responding features are different due to the different physical processes off the coast of the eastern and western Pacific Ocean.In the western Pacific Ocean,when the westward trade winds relax,a eastward propagating wave quickly develops.At the same time,a westward traveling wave also excites in the eastern Pacific Ocean,but nomatter how the speed and amplitude,the eastward propagating wave is bigger than the westward traveling one,the eastward wave can rapidly affect on the central part of the Pacific Ocean,i.e.,the western Pacific Ocean is easy to be the source of El Niño events,especially the strong El Niño events.
In general,El Niño refers to the appearance of unusual high sea surface temperature in the eastern tropical Pacific Ocean.But in recent El Niño events(for example,1982/1983 and 1986/1987),the warm sea surface temperature anomaly first appears in the western Pacific Ocean and then expands eastward.That is to say,the El Niño events are not only confined to the eastern tropical Pacific Ocean.Based on the above facts,a baroclinic two layers ocean model is developed and used to study the responding characteristics of equatorial eastern and western Pacific Ocean to relaxation of trade winds.The results show the responding features are different due to the different physical processes off the coast of the eastern and western Pacific Ocean.In the western Pacific Ocean,when the westward trade winds relax,a eastward propagating wave quickly develops.At the same time,a westward traveling wave also excites in the eastern Pacific Ocean,but nomatter how the speed and amplitude,the eastward propagating wave is bigger than the westward traveling one,the eastward wave can rapidly affect on the central part of the Pacific Ocean,i.e.,the western Pacific Ocean is easy to be the source of El Niño events,especially the strong El Niño events.
2003, 25(5): 38-48,57.
Abstract:
To meet the increasing demand of national spatial database infrastructure construction and application,a concept model of China's coastal zone science data platform is established based on the information feature analysis of a compound dataset consisted of remote sensing data and conventional data of coast zone and offshore.Based on this concept model,the detailed logical database structure and the storage strategy of remote sensing data and its metadata using ARCSDEare desig ned.The complicated technology of multi-sources data combination in this research is crucial to the future coastal zone and offshore database construction and practical running,which will provide intelligent information analysis and technological service for coastal zone and offshore investigation,research,development and management.
To meet the increasing demand of national spatial database infrastructure construction and application,a concept model of China's coastal zone science data platform is established based on the information feature analysis of a compound dataset consisted of remote sensing data and conventional data of coast zone and offshore.Based on this concept model,the detailed logical database structure and the storage strategy of remote sensing data and its metadata using ARCSDEare desig ned.The complicated technology of multi-sources data combination in this research is crucial to the future coastal zone and offshore database construction and practical running,which will provide intelligent information analysis and technological service for coastal zone and offshore investigation,research,development and management.
2003, 25(5): 49-57.
Abstract:
The accuracy of satellite measured sea surface temperature(SST)is the key for both SSTalgorithms and applications,which is reported to reach 0.5℃.In fact,the accuracy of satellite measured SSTis affected by many factors,it is very difficult to obtain root mean square(RMS)error within 1℃ in an operational satellite SST application system.Many values of SST are found to be much lower than temperature measured by the ships in evaluating the accuracy of SSTderived from NOAA satellite data.The error distribution shows that larger negative values of temperature bias take up a high proportion with the maximum up to -17.2℃.Many patches of low temperature abnormality,distributing in the SST images,are caused by thin clouds or fogs,which may be mistakenly taken as eddy or front.The temperature abnormality is very difficult to be detected by SST inversion algorithm and cloud detection technology.A temperature error control technology is developed employing standard reference temperature images to detect the temperature abnormality.This method can efficiently detect the temperature abnor mality to remove the abnormal low values of SST and improve the accuracy of satellite measured SST.The RM Serror is improved from 5.71 to 1.75℃ in an operational SST system.It has been applied to drawing the fishery chart products of the North Pacific.
The accuracy of satellite measured sea surface temperature(SST)is the key for both SSTalgorithms and applications,which is reported to reach 0.5℃.In fact,the accuracy of satellite measured SSTis affected by many factors,it is very difficult to obtain root mean square(RMS)error within 1℃ in an operational satellite SST application system.Many values of SST are found to be much lower than temperature measured by the ships in evaluating the accuracy of SSTderived from NOAA satellite data.The error distribution shows that larger negative values of temperature bias take up a high proportion with the maximum up to -17.2℃.Many patches of low temperature abnormality,distributing in the SST images,are caused by thin clouds or fogs,which may be mistakenly taken as eddy or front.The temperature abnormality is very difficult to be detected by SST inversion algorithm and cloud detection technology.A temperature error control technology is developed employing standard reference temperature images to detect the temperature abnormality.This method can efficiently detect the temperature abnor mality to remove the abnormal low values of SST and improve the accuracy of satellite measured SST.The RM Serror is improved from 5.71 to 1.75℃ in an operational SST system.It has been applied to drawing the fishery chart products of the North Pacific.
2003, 25(5): 58-64.
Abstract:
The development of beach is not convenient owing to the fact that it spreads widely and varies frequently, and routine topography data lack.The Dachan Bay of Lingdingyang estuary is taken as research area,and data resources such as MSS,TM and ETM are provided by American Landsat,the time span of these data is from 1978 to 2001,totaling 17 time span The shoreline variation of the Dachan Bay,beach zoning and its area estimating,beach utilization,and velocity of deposition are determined for the first time in China by applying waterside line elevation reverse technology based on multi-temporal satellite remote-sensing images.The gradient and the deposition velocity of the target beaches at different locations are successfully reversed.The research conclusion provides the theory foundation for the develpment of the Dachan Bay in the Shenzhen Harbor.
The development of beach is not convenient owing to the fact that it spreads widely and varies frequently, and routine topography data lack.The Dachan Bay of Lingdingyang estuary is taken as research area,and data resources such as MSS,TM and ETM are provided by American Landsat,the time span of these data is from 1978 to 2001,totaling 17 time span The shoreline variation of the Dachan Bay,beach zoning and its area estimating,beach utilization,and velocity of deposition are determined for the first time in China by applying waterside line elevation reverse technology based on multi-temporal satellite remote-sensing images.The gradient and the deposition velocity of the target beaches at different locations are successfully reversed.The research conclusion provides the theory foundation for the develpment of the Dachan Bay in the Shenzhen Harbor.
2003, 25(5): 65-75.
Abstract:
The decay dynamic equations of two daug hters are resolved as initial activities of daughters are not zero, and calculation formula of activities for measuring uranium and thorium series of disequilibrium using spectrosopy is given.238U,234Th,226Ra,222Rn,228Ra,228Th,224Ra,212Pb,210Pb and 40K in two sediment samples are determined as application.
The decay dynamic equations of two daug hters are resolved as initial activities of daughters are not zero, and calculation formula of activities for measuring uranium and thorium series of disequilibrium using spectrosopy is given.238U,234Th,226Ra,222Rn,228Ra,228Th,224Ra,212Pb,210Pb and 40K in two sediment samples are determined as application.
2003, 25(5): 76-82.
Abstract:
Nitrogen and phosphorus are the elements which are the basis of phytoplanktons'growth.These elements are removed by the phytoplankton in the upper water.When the phytoplankton and some organic debris subside, these elements are regenerated by biologic oxidation,so the distributed characteristic of the contents is that the contents increase by degrees from upper to bottom in the water column.Of course,the distribution of nutrients is connected with different sea areas. Although the south sea is researched time after time and many data of nutrients are got,the study of the distribution and the regeneration of these parameters are short,so the data got by two cruises in June and November of 1998 are used to study some characteristics of those nutrients.On the basis of analyzing the vertical distribution of the nutrients,the relationship between AOU(apparent oxygen utilization)and those nutrients is got.The result shows that during organic matter regenerating,the mixing water otfers water body whose depth is about 75~1 000 mextra oxygen and the vertical variation of those nutrients in the water column are mostly influenced by regeneration.The efficiency of oxygen's supplement takes place between the depth of 1 000 m and 2 700 m,but the proportion of the regenerated nutrients in water becomes little.
Nitrogen and phosphorus are the elements which are the basis of phytoplanktons'growth.These elements are removed by the phytoplankton in the upper water.When the phytoplankton and some organic debris subside, these elements are regenerated by biologic oxidation,so the distributed characteristic of the contents is that the contents increase by degrees from upper to bottom in the water column.Of course,the distribution of nutrients is connected with different sea areas. Although the south sea is researched time after time and many data of nutrients are got,the study of the distribution and the regeneration of these parameters are short,so the data got by two cruises in June and November of 1998 are used to study some characteristics of those nutrients.On the basis of analyzing the vertical distribution of the nutrients,the relationship between AOU(apparent oxygen utilization)and those nutrients is got.The result shows that during organic matter regenerating,the mixing water otfers water body whose depth is about 75~1 000 mextra oxygen and the vertical variation of those nutrients in the water column are mostly influenced by regeneration.The efficiency of oxygen's supplement takes place between the depth of 1 000 m and 2 700 m,but the proportion of the regenerated nutrients in water becomes little.
2003, 25(5): 83-91.
Abstract:
Data of sediment discharge from 1951 to 2000 and bathymetric maps of a major portion to the subaqueous delta surveyed in 1958,1978 and 1998 are utilized to study variation in river sediment supply and morphological response to the subaqueous delta.Since the end of 1960s,sediment discharge at Sta.Datong has shown a significant decreasing trend,one third lower in the 1990s than in the 1960s.The reduction in sediment supply is found to have resulted from dam construction in the drainage.As a response to this reduction,vertical accretion rate of the subaqueous delta front has been decreased from 55 mm/a during 1958~1978 to 11 mm/a during 1978~1998.Meanwhile,severe erosion has occurred on the outer mar gin of the subaqueous delta.It is predicted that river sediment discharge will probably be reduced to 40% and 60% of the present(the average of the past 50 a)respectively in the first half and the second half of this century due to human activities especially the Three Gorges Project.As a result, the total prog radation rate of the delta will be dramatically reduced and local severe erosion may be inevitable.
Data of sediment discharge from 1951 to 2000 and bathymetric maps of a major portion to the subaqueous delta surveyed in 1958,1978 and 1998 are utilized to study variation in river sediment supply and morphological response to the subaqueous delta.Since the end of 1960s,sediment discharge at Sta.Datong has shown a significant decreasing trend,one third lower in the 1990s than in the 1960s.The reduction in sediment supply is found to have resulted from dam construction in the drainage.As a response to this reduction,vertical accretion rate of the subaqueous delta front has been decreased from 55 mm/a during 1958~1978 to 11 mm/a during 1978~1998.Meanwhile,severe erosion has occurred on the outer mar gin of the subaqueous delta.It is predicted that river sediment discharge will probably be reduced to 40% and 60% of the present(the average of the past 50 a)respectively in the first half and the second half of this century due to human activities especially the Three Gorges Project.As a result, the total prog radation rate of the delta will be dramatically reduced and local severe erosion may be inevitable.
2003, 25(5): 92-96.
Abstract:
Agglutinin has been shown to exist in the serum of bivalve Scapharca subcrenata.The agglutinin showed agglutinating activity against human A,B,O,chicken and mouse erythrocytes,the agglutinintiters were 256,256, 8,16,64 respectively.The serum could also agglutinate microorganisms,such as Candida albicans,Sacchar omycescer evisiae,Vibrio alginolyticus.The experiment showed that the agglutinin was stable at a wide range of temperature and pH degree.The activity of the agglutinin could be inhibited by L-rhamnose,L-arabinose,maltose, Dgalactose and sucrose.When the animals were infected by Vibrio sp.,their serum showed agglutinating titers in crease.
Agglutinin has been shown to exist in the serum of bivalve Scapharca subcrenata.The agglutinin showed agglutinating activity against human A,B,O,chicken and mouse erythrocytes,the agglutinintiters were 256,256, 8,16,64 respectively.The serum could also agglutinate microorganisms,such as Candida albicans,Sacchar omycescer evisiae,Vibrio alginolyticus.The experiment showed that the agglutinin was stable at a wide range of temperature and pH degree.The activity of the agglutinin could be inhibited by L-rhamnose,L-arabinose,maltose, Dgalactose and sucrose.When the animals were infected by Vibrio sp.,their serum showed agglutinating titers in crease.
2003, 25(5): 97-102.
Abstract:
Genetic variation of three wild stocks of Meretrix meretrix was analysed using random amplified polymorphic DNA(RAPD)markers,50 primers got amplified bands in total of 60 primers,amplified bands of 15 primers were selected as statistic similarity index and genetic distances.Genetic distances of intra stock of Liaonin,Jiangsu Province and the Zhuang Autonomous Region of Guangxi are 0.169±0.034,0.117±0.032 and 0.108±0.031,respectively;and those of inter stock of Liaonin-Jiangsu,Jiangsu-Guangxi and Guangxi-Liaonin are 0.222± 0.036,0.209±0.013 and 0.316±0.047,respectively,the results show that genetic distances of three stock in crease with distance increase.The marker of s396-900 bp is owned by Jiangsu and Liaonin stocks,and marker of s433-250 bp is owned by Jiangsu and Guangxi stocks,three stocks were indentified by this two markers.
Genetic variation of three wild stocks of Meretrix meretrix was analysed using random amplified polymorphic DNA(RAPD)markers,50 primers got amplified bands in total of 60 primers,amplified bands of 15 primers were selected as statistic similarity index and genetic distances.Genetic distances of intra stock of Liaonin,Jiangsu Province and the Zhuang Autonomous Region of Guangxi are 0.169±0.034,0.117±0.032 and 0.108±0.031,respectively;and those of inter stock of Liaonin-Jiangsu,Jiangsu-Guangxi and Guangxi-Liaonin are 0.222± 0.036,0.209±0.013 and 0.316±0.047,respectively,the results show that genetic distances of three stock in crease with distance increase.The marker of s396-900 bp is owned by Jiangsu and Liaonin stocks,and marker of s433-250 bp is owned by Jiangsu and Guangxi stocks,three stocks were indentified by this two markers.
2003, 25(5): 103-112.
Abstract:
Based on the two cruises of Sino-Germany cooperative ecosystem surveys which were carried out in the Bohai Sea(37°～41°N,117.5°～122.5°E)in September 1998 and April 1999,and a mont hly monitoring investigation at the Penglai and Changdao Island,the distribution and variations of phytoplankton size-fractionated biomass were studied.The size-fractionated chlorophyll a was measured.Phytoplankton was classified with four size fractions as follows:netphytoplankton,>76μm(the standard mesh size of phytoplankton net used in China);small netphy-toplankton,20～76μm;nanophytoplankton,2～20μm;picophytoplankton,0.2～2.0μm.The percentage of chlorophyll a concentrations of the four size fraction in the survey area are(31.11±11.46)%,(18.95±9.76)%,(33.06±10.71)% and (16.88±8.52)% (n=239) respectively in the autumn of 1998,and (13.34±7.48)%,(16.87±5.57)%,(52.95±13.51)% and (16.84±13.26)% (n=259) respectively in the spring of 1999.The netphytoplankton and small netphytoplankton can be combined into microphytoplankton. This result shows that the nanophytoplankton is the most important primary producer in spring and microphyto-plankton is the most important one in autumn in the Bohai Sea.The smallest picophytoplankton cannot be neglected and took a percentage of 17% compared with the other phytoplankton size components.The vertical profile patterns of size-fractionated chlorophyll a concentration of Transects 1 and 2 in the survey area show that microphytoplankton usually occupies in the upper water layer.The annual variation of size-fractionated chlorophyll a concentrations in the Bohai Straits show that:high values of chlorophyll a concentrations of netphytoplankton appear in April and July, the maximum is in April;high values of chlorophyll a concentrations of small netphytoplankton appear in June and November,the maximum is in June;similar high values of chlorophyll a concentrations of nanophytoplankton appear in April and November;and high values of chlorophyll a concentrations of picophytoplankton appear in September. The chlorophyll a contribution to total of the various size of phytoplankton in the survey area shows that microphyto-plankton is relatively important primary producer compared with the other regions.
Based on the two cruises of Sino-Germany cooperative ecosystem surveys which were carried out in the Bohai Sea(37°～41°N,117.5°～122.5°E)in September 1998 and April 1999,and a mont hly monitoring investigation at the Penglai and Changdao Island,the distribution and variations of phytoplankton size-fractionated biomass were studied.The size-fractionated chlorophyll a was measured.Phytoplankton was classified with four size fractions as follows:netphytoplankton,>76μm(the standard mesh size of phytoplankton net used in China);small netphy-toplankton,20～76μm;nanophytoplankton,2～20μm;picophytoplankton,0.2～2.0μm.The percentage of chlorophyll a concentrations of the four size fraction in the survey area are(31.11±11.46)%,(18.95±9.76)%,(33.06±10.71)% and (16.88±8.52)% (n=239) respectively in the autumn of 1998,and (13.34±7.48)%,(16.87±5.57)%,(52.95±13.51)% and (16.84±13.26)% (n=259) respectively in the spring of 1999.The netphytoplankton and small netphytoplankton can be combined into microphytoplankton. This result shows that the nanophytoplankton is the most important primary producer in spring and microphyto-plankton is the most important one in autumn in the Bohai Sea.The smallest picophytoplankton cannot be neglected and took a percentage of 17% compared with the other phytoplankton size components.The vertical profile patterns of size-fractionated chlorophyll a concentration of Transects 1 and 2 in the survey area show that microphytoplankton usually occupies in the upper water layer.The annual variation of size-fractionated chlorophyll a concentrations in the Bohai Straits show that:high values of chlorophyll a concentrations of netphytoplankton appear in April and July, the maximum is in April;high values of chlorophyll a concentrations of small netphytoplankton appear in June and November,the maximum is in June;similar high values of chlorophyll a concentrations of nanophytoplankton appear in April and November;and high values of chlorophyll a concentrations of picophytoplankton appear in September. The chlorophyll a contribution to total of the various size of phytoplankton in the survey area shows that microphyto-plankton is relatively important primary producer compared with the other regions.
2003, 25(5): 113-124.
Abstract:
According to the characteristics of the complicate bathymetry,hydrology and sediment movement in the Changjiang Estuary,a two-dimensional numerical model for total sediment transport and sedbed evolution under waves and currents are developed.Based on the rational calculation of currents in the study area,the method of shear stress is adopted to determine the source function in the suspended sediment diffusion equation.Through a series of the numerical experiments and the statistical analyses of the observed field data,a local coefficient,which can reflect the bottom material and consolidation,is introduced into the classic critical erosion velocity of the sediment. The floc settling velocity of sediment particles is taken as the function of current velocity,salinity and suspended sediment concentration,which can improve the calculation precision of the suspended sediment numerical simulation in the Changjiang Estuary.In the computation of bed-load sediment transport,a rational method for determining the related parameters is developed.The verification of hydrology and sediment data shows that the model can preferably reflect the current field,sediment field and bathymetry evaluation in the Changjiang Estuary.
According to the characteristics of the complicate bathymetry,hydrology and sediment movement in the Changjiang Estuary,a two-dimensional numerical model for total sediment transport and sedbed evolution under waves and currents are developed.Based on the rational calculation of currents in the study area,the method of shear stress is adopted to determine the source function in the suspended sediment diffusion equation.Through a series of the numerical experiments and the statistical analyses of the observed field data,a local coefficient,which can reflect the bottom material and consolidation,is introduced into the classic critical erosion velocity of the sediment. The floc settling velocity of sediment particles is taken as the function of current velocity,salinity and suspended sediment concentration,which can improve the calculation precision of the suspended sediment numerical simulation in the Changjiang Estuary.In the computation of bed-load sediment transport,a rational method for determining the related parameters is developed.The verification of hydrology and sediment data shows that the model can preferably reflect the current field,sediment field and bathymetry evaluation in the Changjiang Estuary.
2003, 25(5): 125-135.
Abstract:
Since the 1970s,the sediment flux of the Huanghe River into the sea has shown a marked tendency of decrease,which is unfavor able to the wetland protection and oil extraction in the Huanghe River Delta.Thus,effort is made to elucidate the relation between the sediment flux into the sea and the drainage basin factors including climate and human activities.The results show that the sediment flux into the sea responds to the changed precipitation in different ways for different water and sediment producing areas in the drainage basin.Other factors are given as constant,when the annual precipitation in the area between Longmen and Sanmenx ia decreases by 10 mm,the sediment flux into the sea will decrease by 27.5 Mt/a;when the precipitation in the area between Hekouzhen and Longmen decreases by 10 mm,the sediment flux into the sea will decrease by 14.3 Mt/a;when the precipitation in the area above Lanzhou decreases by 10 mm,the sediment flux into the sea will decrease by 17.4 Mt/a.Amultiple regression equation has been established between the sediment flux into the sea and the influencing factors,such as the area of terrace land building and tree-and grass-planting,the area of the land created by the sediment trapped by checkdams,the annual precipitation and the annual quantity of water diversion by man.The equation may be used to estimate the change in the sediment flux into the sea when the influencing variables are further changed,to provide useful knowledge for the environmental planning of the Huanghe River drainage basin and its delta.
Since the 1970s,the sediment flux of the Huanghe River into the sea has shown a marked tendency of decrease,which is unfavor able to the wetland protection and oil extraction in the Huanghe River Delta.Thus,effort is made to elucidate the relation between the sediment flux into the sea and the drainage basin factors including climate and human activities.The results show that the sediment flux into the sea responds to the changed precipitation in different ways for different water and sediment producing areas in the drainage basin.Other factors are given as constant,when the annual precipitation in the area between Longmen and Sanmenx ia decreases by 10 mm,the sediment flux into the sea will decrease by 27.5 Mt/a;when the precipitation in the area between Hekouzhen and Longmen decreases by 10 mm,the sediment flux into the sea will decrease by 14.3 Mt/a;when the precipitation in the area above Lanzhou decreases by 10 mm,the sediment flux into the sea will decrease by 17.4 Mt/a.Amultiple regression equation has been established between the sediment flux into the sea and the influencing factors,such as the area of terrace land building and tree-and grass-planting,the area of the land created by the sediment trapped by checkdams,the annual precipitation and the annual quantity of water diversion by man.The equation may be used to estimate the change in the sediment flux into the sea when the influencing variables are further changed,to provide useful knowledge for the environmental planning of the Huanghe River drainage basin and its delta.
2003, 25(5): 136-140.
Abstract:
2003, 25(5): 141-146.
Abstract:
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