On the basis of hydrographic data obtained in August 2000 cruise, the circulation in the South China Sea (SCS) is computed by the modified inverse method in combination with SSH data from TOPEX/ERS-2 analysis. For stu...On the basis of hydrographic data obtained in August 2000 cruise, the circulation in the South China Sea (SCS) is computed by the modified inverse method in combination with SSH data from TOPEX/ERS-2 analysis. For study of the dynamical mechanism, which causes the pattern of summer circulation in the SCS, the diagnostic model (Yuan et al. 1982. Acta Oceanologica Sinica,4(1):1-11; Yuan and Su. 1992. Numerical Computation of Physical Oceanography.474-542) is used to simulate numerically the summer circulation in the SCS. The following results have been obtained. (1) The central and southwestern SCSs are dominated mainly by anticy-clonic circulation systems. They are mainly as follows. 1) There is strong anticyclonic eddy southeast of Vietnam (W1). Its horizontal scale is about 300 km, and it extends vertically from the surface to the about 1 000 m level. 2) There are a warm eddy W2 southeast of Zhongsha Islands and the anticyclonic circulation system W3 west off the Luzon Island. 3) There is a stronger cyclonic eddy C1 between the anticyclonic eddies W1 and W2.4) A strong northward coastal jet is present near the coast of Vietnam, and separates from the coast of Vietnam at about 12° N to the northeast.(2)The northern SCS is dominated mainly by a cyclonic circulation system. There is a cyclonic circulation system near and north of Section N2. (3) The southeastern SCS is dominated mainly by the cyclonic circulation system. (4) Comparing the results of circulation in the SCS during the summer of 2000 with those during the summer of 1998, it is found that they agree qualitatively, but there is the some difference between them in quantity.This shows that the circulation in the SCS has obviously seasonal feature. (5) The dynamical mechanism which products the basic pattern of summer circulation is because the following two reasons: 1) the joint effect of the baroclinity and relief (JEBAR) is essential dynamical cause; and 2) it is next important dynamical cause that the interaction between the wind stress and bottom topography under the southerly monsoon. (6) Comparing the hydrographic structure and distribution of stream functions with the SSH data from TOPEX/ERS-2 analysis in the SCS during August of 2000, they agree qualitatively.展开更多
Direct measurements of current velocity and water temperature were undertaken at the mooring Sta. M (125°29.38' N, 31°49.70' E) on the continental shelf area in the East China Sea in June 1999 by R/V...Direct measurements of current velocity and water temperature were undertaken at the mooring Sta. M (125°29.38' N, 31°49.70' E) on the continental shelf area in the East China Sea in June 1999 by R/V Xiangyanghong 14. The relationship between various time series of oceanic fluctuations is calculated by spectral analysis. The major results are as follows: (1) an average (u,v) of (6.9,-3.0 cm/s) at the 30 m depth is obtained during the 9-day observation, and that at the 45 m depth is (3.7,-1.1 cm/s), i. e., the mean flows are southeastward at both the 30 and 45 m depths;the currents become stronger gradually during the observation period; this may be mainly attributed to the transition of the tidal currents from neap to spring; (2)semidiurnal fluctuation is the most dominant in the current fluctuations, and rotates mainly clockwise; in the next place, there is also diurnal fluctuation;the local inertial period is close to the period of diurnal fluctuation, and an inertial motion is clockwise; thus, local inertial motion combines with diurnal fluctuation, and makes the spectral peaks in clockwise components much higher than those in counterclockwise ones; except for the fluctuations of above main periods, there is also the peak at 3 d period for counterclockwise compo-nents in the upper and lower layers; (3) the calculation of cross spectra between two time series of current velocities at the 30 and 45 m depths shows that both the current fluctuations at the 30 and 45 m depths are much alike, i. e., they are synchro; this shows that the flow field here is rather vertically homogeneous; (4)power spectra of tempera-ture time series at both the 30 and 45 m depths show that the semidiurnal peak is the most predominant, and the second highest peak is the diurnal period; besides spectral peaks at above periods, there are also obvious spectral peaks at 6.8 h and 2 d; (5)plots of temperature time series at 16 , 30 , 35 , 45 and 50 m depths show that the temporal variations of temperature at these depths are synchro, which are like those in the velocity field; temperature records also show a gradual rise in temperature, which are also like those in the velocity field.展开更多
On the basis of the current measurements at 200,500 and 800 m from moored current meters with the time series data from March 17 to April 15 at the mooring station (20°49′57″N, 120°48′ 12″E) and the hydr...On the basis of the current measurements at 200,500 and 800 m from moored current meters with the time series data from March 17 to April 15 at the mooring station (20°49′57″N, 120°48′ 12″E) and the hydrographic data obtained in the Luzon Strait during the spring of 2002 cruise, the circulation in the investigated area is computed by using the modified inverse method. The major observed results are as follows: (1) the average velocity and the flow direction in the observing days are (47.4 cm/s, 346°) at the 200 m level. The average velocity in the observing days is (20.3 cm/s, 350? at the 500 m level. These mean that the Kuroshio intrudes into the South Chin Sea to flow northwestward through the Luzon Strait at 200 and 500 m levels. (2) The average velocity in the observing days is (1.2 cm/s, 35°) at the 800 m level, i. e., its direction is northeastward. This means that the flow condition at the 800 m level very differs from mat at the 200 and 500 m levels. (3) There is the high density and cold water (HDCW) in the middle of western part of in the investigated region, and its center is located near the hydrological station 3 at Section A. (4) There is the lower density and warm water (LDWW) in the southeastern part of investigated region. (5) The currents in April 2002 are stronger than those in March 2002.The major computed results are as follows: (1) The northwestward and southeastward VTs through Section B are 32.48×106 m3/s (inclusive of VT of anticyclonic eddy) and 3.34×106m3/s, respectively. The net northwestward VT through Section B in the investigated area is about 29.14×106 m3/s. (2) The eastern and western VTs through Section A are about 16.71×106 and 8.57×106 m3/s, respectively. Thus, the net eastward VT through Section A is about 8.14×106 m3/s. (3) The net northward VT through Section M is about 24.68×106 m3/s. (4) After about 24.68×106 m3/s flows through Section M, most of it, about 16.54×106 m3/s, flows northward through the eastern part of Section C and then flows northward into the region east Taiwan Island. The other part of it, about 8.14×106 m3/s, branches out from the main Kuroshio and then flows meanderingly through the western part of Section C. Thus, the Kuroshio has the two cores of current at Section C. (5) The direction of the computed current near the mooring station M agrees with the direction of the current measurements at 200 and 500 m from moored current meters, i.e., their directions both are northwestward. (6) About 3.34×106 m3/s of the South Chin Sea water probably flows slowly from the northwest to the southeast in the layer below 550 m at the western part of Section B.展开更多
基金the Major State Basic Research Program of China un der contract No.G1999043805.
文摘On the basis of hydrographic data obtained in August 2000 cruise, the circulation in the South China Sea (SCS) is computed by the modified inverse method in combination with SSH data from TOPEX/ERS-2 analysis. For study of the dynamical mechanism, which causes the pattern of summer circulation in the SCS, the diagnostic model (Yuan et al. 1982. Acta Oceanologica Sinica,4(1):1-11; Yuan and Su. 1992. Numerical Computation of Physical Oceanography.474-542) is used to simulate numerically the summer circulation in the SCS. The following results have been obtained. (1) The central and southwestern SCSs are dominated mainly by anticy-clonic circulation systems. They are mainly as follows. 1) There is strong anticyclonic eddy southeast of Vietnam (W1). Its horizontal scale is about 300 km, and it extends vertically from the surface to the about 1 000 m level. 2) There are a warm eddy W2 southeast of Zhongsha Islands and the anticyclonic circulation system W3 west off the Luzon Island. 3) There is a stronger cyclonic eddy C1 between the anticyclonic eddies W1 and W2.4) A strong northward coastal jet is present near the coast of Vietnam, and separates from the coast of Vietnam at about 12° N to the northeast.(2)The northern SCS is dominated mainly by a cyclonic circulation system. There is a cyclonic circulation system near and north of Section N2. (3) The southeastern SCS is dominated mainly by the cyclonic circulation system. (4) Comparing the results of circulation in the SCS during the summer of 2000 with those during the summer of 1998, it is found that they agree qualitatively, but there is the some difference between them in quantity.This shows that the circulation in the SCS has obviously seasonal feature. (5) The dynamical mechanism which products the basic pattern of summer circulation is because the following two reasons: 1) the joint effect of the baroclinity and relief (JEBAR) is essential dynamical cause; and 2) it is next important dynamical cause that the interaction between the wind stress and bottom topography under the southerly monsoon. (6) Comparing the hydrographic structure and distribution of stream functions with the SSH data from TOPEX/ERS-2 analysis in the SCS during August of 2000, they agree qualitatively.
基金This work was supported by the National Natural Science Foundation of China under contract Nos 40176007 and 49736200the Major State Ba-Sic Research Program of China under contract No.G 1999043802.
文摘Direct measurements of current velocity and water temperature were undertaken at the mooring Sta. M (125°29.38' N, 31°49.70' E) on the continental shelf area in the East China Sea in June 1999 by R/V Xiangyanghong 14. The relationship between various time series of oceanic fluctuations is calculated by spectral analysis. The major results are as follows: (1) an average (u,v) of (6.9,-3.0 cm/s) at the 30 m depth is obtained during the 9-day observation, and that at the 45 m depth is (3.7,-1.1 cm/s), i. e., the mean flows are southeastward at both the 30 and 45 m depths;the currents become stronger gradually during the observation period; this may be mainly attributed to the transition of the tidal currents from neap to spring; (2)semidiurnal fluctuation is the most dominant in the current fluctuations, and rotates mainly clockwise; in the next place, there is also diurnal fluctuation;the local inertial period is close to the period of diurnal fluctuation, and an inertial motion is clockwise; thus, local inertial motion combines with diurnal fluctuation, and makes the spectral peaks in clockwise components much higher than those in counterclockwise ones; except for the fluctuations of above main periods, there is also the peak at 3 d period for counterclockwise compo-nents in the upper and lower layers; (3) the calculation of cross spectra between two time series of current velocities at the 30 and 45 m depths shows that both the current fluctuations at the 30 and 45 m depths are much alike, i. e., they are synchro; this shows that the flow field here is rather vertically homogeneous; (4)power spectra of tempera-ture time series at both the 30 and 45 m depths show that the semidiurnal peak is the most predominant, and the second highest peak is the diurnal period; besides spectral peaks at above periods, there are also obvious spectral peaks at 6.8 h and 2 d; (5)plots of temperature time series at 16 , 30 , 35 , 45 and 50 m depths show that the temporal variations of temperature at these depths are synchro, which are like those in the velocity field; temperature records also show a gradual rise in temperature, which are also like those in the velocity field.
基金the Major State Basic Research Program of China under contact No.G 1999043805.
文摘On the basis of the current measurements at 200,500 and 800 m from moored current meters with the time series data from March 17 to April 15 at the mooring station (20°49′57″N, 120°48′ 12″E) and the hydrographic data obtained in the Luzon Strait during the spring of 2002 cruise, the circulation in the investigated area is computed by using the modified inverse method. The major observed results are as follows: (1) the average velocity and the flow direction in the observing days are (47.4 cm/s, 346°) at the 200 m level. The average velocity in the observing days is (20.3 cm/s, 350? at the 500 m level. These mean that the Kuroshio intrudes into the South Chin Sea to flow northwestward through the Luzon Strait at 200 and 500 m levels. (2) The average velocity in the observing days is (1.2 cm/s, 35°) at the 800 m level, i. e., its direction is northeastward. This means that the flow condition at the 800 m level very differs from mat at the 200 and 500 m levels. (3) There is the high density and cold water (HDCW) in the middle of western part of in the investigated region, and its center is located near the hydrological station 3 at Section A. (4) There is the lower density and warm water (LDWW) in the southeastern part of investigated region. (5) The currents in April 2002 are stronger than those in March 2002.The major computed results are as follows: (1) The northwestward and southeastward VTs through Section B are 32.48×106 m3/s (inclusive of VT of anticyclonic eddy) and 3.34×106m3/s, respectively. The net northwestward VT through Section B in the investigated area is about 29.14×106 m3/s. (2) The eastern and western VTs through Section A are about 16.71×106 and 8.57×106 m3/s, respectively. Thus, the net eastward VT through Section A is about 8.14×106 m3/s. (3) The net northward VT through Section M is about 24.68×106 m3/s. (4) After about 24.68×106 m3/s flows through Section M, most of it, about 16.54×106 m3/s, flows northward through the eastern part of Section C and then flows northward into the region east Taiwan Island. The other part of it, about 8.14×106 m3/s, branches out from the main Kuroshio and then flows meanderingly through the western part of Section C. Thus, the Kuroshio has the two cores of current at Section C. (5) The direction of the computed current near the mooring station M agrees with the direction of the current measurements at 200 and 500 m from moored current meters, i.e., their directions both are northwestward. (6) About 3.34×106 m3/s of the South Chin Sea water probably flows slowly from the northwest to the southeast in the layer below 550 m at the western part of Section B.
