Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for consti...Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for constituents M 2, S 2, O 1, K 1, M 4 and MS 4. The mean sea heights above the reference ellipsoid were also obtained consequently. The obtained tidal constants were compared with those from deep sea and island tide gauge data. The rms differences between the harmonic constants derived from Geosat altimetry and deep sea tide gauges for M 2, S 2, O 1 and K 1 ranged from 1.4 cm to 2.6 cm, although the GM altimeter data have significant errors due to instrument malfunction and other reasons. M 2 tide obtained was the most accurate one among all the tides. Comparison also showed that island tidal constants cannot represent well the tidal distribution in the ocean near the island, because of the significant local effect on tides.展开更多
The Nampo dike, which is located at the west coast of Korea, was destroyed by wave overtopping during the storms on 30 August and 17 September in 1959. In this paper, is performed the probabilistic assessment of wave ...The Nampo dike, which is located at the west coast of Korea, was destroyed by wave overtopping during the storms on 30 August and 17 September in 1959. In this paper, is performed the probabilistic assessment of wave overtopping of Nampo dike by use of Owen model, Van der Meer ＆ Janssen model and Hedges ＆ Reis model for wave overtopping of seawall. Based on the available tidal and wave data for storm surges in 1989, the risk assessment of wave overtopping of the Nampo dike has been carried out by both Level Ⅱ and Level Ⅲ reliability methods. The calculated resuhs show the general agreement of failure probability between the two methods. By utilizing the rehabilitated cross section of Nampo dike, the failure probability of wave overtopping for the Nampo dike after rehabilitation will be rapidly reduced to that of initial design at crest level of 9.0 m with the improved slope from 1 ： 2 to 1 ： 4 at seaside. Since the sea level may only rise 1.0 m in the next few decades, the failure probability of Nampo dike will be still in the safe range.展开更多
A coupled sea ice-mixed layer-isopycnal model (OPYC, alias PIPE) was applied to simulate the circulation in the Southern Ocean. The model domain covered the Southern Ocean south of 24°S. The model was first spun ...A coupled sea ice-mixed layer-isopycnal model (OPYC, alias PIPE) was applied to simulate the circulation in the Southern Ocean. The model domain covered the Southern Ocean south of 24°S. The model was first spun up in a coarse resolution grid (2° longitude×1°latitude) for 40 years running; then was shifted into a fine resolution grid (1°longitude×0.5°latitude with a focus in the Indian Sector and the Antarctic Marginal Sea) for additional 5 years running in order to creat the detailed circulation pattern in the area of interest. The simulated annual averaged volume transport through Drake Passage was 145.3×106m 3/s and more similar to the observed result (134×106m 3/s) than FRAM’s result (about 200×106m 3/s). The simulated results of circulation and sea ice also agreed with those of previous results. The meridional streamfuction and meridional transport obtained from the simulated results were used to study the meridional characteristics of the Antarctic Circumpolar Current(ACC). The ACC is traditionally considered to be a zonal current. However, the modeled result showed the ACC’s significant non-zonal feature in some regions, such as the Kerguelen Plateau in the Indian Sector. Arranged in a staggered way, the northward and southward transport areas occur in the ACC region. The isopycnals go up in the northward transport areas and go down in the southward transport areas, which implied a spiral motion of fluid particles in the ACC. This spiral motion is caused by the non-zonal feature of the ACC and is constructed by the ACC’s north and south shifts in several regions of the Southern Ocean not only the Drake Passage. Though most meridional motions are limited in the ACC region, some meridional exchange channels across the ACC might exist in some areas, for example, in the Southeast Australian Basin near 150°E. The meridional streamfuction shows the Subtropical Cell, the Deacon Cell, the Subpolar Cell and the Polar Cell, but misses the Deep Cell. All the cells change with seasons. The Deacon Cell and the Subpolar Cell connect with each other in summer but are separate in the other three seasons. Their ranges are smaller in summer and larger in winter. In contrast, the Polar Cell’s range covers a quite large region between the Antarctic coast and 64°S in summer but becomes smaller in winter, which implies that the Polar Cell is related to the sea ice’s melt process.展开更多
The monthly and annual mean freshwater, heat and salt transport through the openboundaries of the South and East China Seas derived from a variable-grid global ocean circulation model is reported. The model has 1/6 re...The monthly and annual mean freshwater, heat and salt transport through the openboundaries of the South and East China Seas derived from a variable-grid global ocean circulation model is reported. The model has 1/6 resolution for the seas adjacent to China and 3 resolution for the global ocean. The model results are in fairly good agreement with the existing estimates based on measurements. The computation shows that the flows passing through the South China Sea contribute volume, heat and salt transport of 5.3 Sv, 0.57 PW and 184 Ggs-1, respectively (about 1/4) to the Indonesian Throughflow, indicating that the South China Sea is an important pathway of the Pacific to Indian Ocean throughflow. The volume, heat and salt transport of the Kuroshio in the East China Sea is 25.6 Sv, 2.32 PW and 894 Ggs-1, respectively. Less than 1/4 of this transport passes through the passage between Iriomote and Okinawa. The calculation of heat balance indicates that the South China Sea absorbs net heat flux from the sun and atmosphere with a rate of 0.08 PW, while the atmosphere gains net heat flux from the Baohai, Yellow and East China Seas with a rate of 0.05 PW.展开更多
A fine-grid model (1/6) covering the South China Sea (SCS), East China Sea and Ja-pan/East Sea, which is embedded into a coarse-grid (3) global model, was established to study the SCS circulation. In the present paper...A fine-grid model (1/6) covering the South China Sea (SCS), East China Sea and Ja-pan/East Sea, which is embedded into a coarse-grid (3) global model, was established to study the SCS circulation. In the present paper, we report the model-produced monthly and annual mean transport stream functions and sea surface heights(SSH) and their anomalies of the SCS. Com-parison to the TOPEX/Poseidon data shows that the model-produced monthly sea surface height anomalies (SSHA) are in good agreement with altimeter measurements. Based on the results, the circulation of the SCS, especially the upper layer circulation, is discussed. In the surface layer, the western Philippine Sea water intrudes into the SCS through the Luzon Strait in autumn, winter and spring, but not in summer. However, as far as the whole water column is concerned, the water in-trudes into the SCS through the Luzon Strait all the year round. This indicates that in summer the water still intrudes into the SCS in the subsurface and intermediate layers. The area near the northern continental slope of the SCS is dominated by a cyclonic circulation all the year round. The SCS Southern Anticyclonic Gyre, SE Vietnam Off-Shore Current in summertime and SCS South-ern Cyclonic Gyre in wintertime are reproduced reasonably. The difference between the monthly averaged SSH and SSHA is significant, indicating the importance of the mean SSH in the SCS circulation.展开更多
文摘Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for constituents M 2, S 2, O 1, K 1, M 4 and MS 4. The mean sea heights above the reference ellipsoid were also obtained consequently. The obtained tidal constants were compared with those from deep sea and island tide gauge data. The rms differences between the harmonic constants derived from Geosat altimetry and deep sea tide gauges for M 2, S 2, O 1 and K 1 ranged from 1.4 cm to 2.6 cm, although the GM altimeter data have significant errors due to instrument malfunction and other reasons. M 2 tide obtained was the most accurate one among all the tides. Comparison also showed that island tidal constants cannot represent well the tidal distribution in the ocean near the island, because of the significant local effect on tides.
基金This project was financially supported by the BK21 Division for U-CITY Construction,Sungkyunkwan University,Korea
文摘The Nampo dike, which is located at the west coast of Korea, was destroyed by wave overtopping during the storms on 30 August and 17 September in 1959. In this paper, is performed the probabilistic assessment of wave overtopping of Nampo dike by use of Owen model, Van der Meer ＆ Janssen model and Hedges ＆ Reis model for wave overtopping of seawall. Based on the available tidal and wave data for storm surges in 1989, the risk assessment of wave overtopping of the Nampo dike has been carried out by both Level Ⅱ and Level Ⅲ reliability methods. The calculated resuhs show the general agreement of failure probability between the two methods. By utilizing the rehabilitated cross section of Nampo dike, the failure probability of wave overtopping for the Nampo dike after rehabilitation will be rapidly reduced to that of initial design at crest level of 9.0 m with the improved slope from 1 ： 2 to 1 ： 4 at seaside. Since the sea level may only rise 1.0 m in the next few decades, the failure probability of Nampo dike will be still in the safe range.
文摘A coupled sea ice-mixed layer-isopycnal model (OPYC, alias PIPE) was applied to simulate the circulation in the Southern Ocean. The model domain covered the Southern Ocean south of 24°S. The model was first spun up in a coarse resolution grid (2° longitude×1°latitude) for 40 years running; then was shifted into a fine resolution grid (1°longitude×0.5°latitude with a focus in the Indian Sector and the Antarctic Marginal Sea) for additional 5 years running in order to creat the detailed circulation pattern in the area of interest. The simulated annual averaged volume transport through Drake Passage was 145.3×106m 3/s and more similar to the observed result (134×106m 3/s) than FRAM’s result (about 200×106m 3/s). The simulated results of circulation and sea ice also agreed with those of previous results. The meridional streamfuction and meridional transport obtained from the simulated results were used to study the meridional characteristics of the Antarctic Circumpolar Current(ACC). The ACC is traditionally considered to be a zonal current. However, the modeled result showed the ACC’s significant non-zonal feature in some regions, such as the Kerguelen Plateau in the Indian Sector. Arranged in a staggered way, the northward and southward transport areas occur in the ACC region. The isopycnals go up in the northward transport areas and go down in the southward transport areas, which implied a spiral motion of fluid particles in the ACC. This spiral motion is caused by the non-zonal feature of the ACC and is constructed by the ACC’s north and south shifts in several regions of the Southern Ocean not only the Drake Passage. Though most meridional motions are limited in the ACC region, some meridional exchange channels across the ACC might exist in some areas, for example, in the Southeast Australian Basin near 150°E. The meridional streamfuction shows the Subtropical Cell, the Deacon Cell, the Subpolar Cell and the Polar Cell, but misses the Deep Cell. All the cells change with seasons. The Deacon Cell and the Subpolar Cell connect with each other in summer but are separate in the other three seasons. Their ranges are smaller in summer and larger in winter. In contrast, the Polar Cell’s range covers a quite large region between the Antarctic coast and 64°S in summer but becomes smaller in winter, which implies that the Polar Cell is related to the sea ice’s melt process.
基金the National Natural Science Foundation of China (Grant No. 49876010) the Major State Basic Research Program (Grant No. G1999043808)+1 种基金 the National Key Science and Technology Pro-ject (Grant No. 97-926-05-01) Youth Fund of the National 863 Project (G
文摘The monthly and annual mean freshwater, heat and salt transport through the openboundaries of the South and East China Seas derived from a variable-grid global ocean circulation model is reported. The model has 1/6 resolution for the seas adjacent to China and 3 resolution for the global ocean. The model results are in fairly good agreement with the existing estimates based on measurements. The computation shows that the flows passing through the South China Sea contribute volume, heat and salt transport of 5.3 Sv, 0.57 PW and 184 Ggs-1, respectively (about 1/4) to the Indonesian Throughflow, indicating that the South China Sea is an important pathway of the Pacific to Indian Ocean throughflow. The volume, heat and salt transport of the Kuroshio in the East China Sea is 25.6 Sv, 2.32 PW and 894 Ggs-1, respectively. Less than 1/4 of this transport passes through the passage between Iriomote and Okinawa. The calculation of heat balance indicates that the South China Sea absorbs net heat flux from the sun and atmosphere with a rate of 0.08 PW, while the atmosphere gains net heat flux from the Baohai, Yellow and East China Seas with a rate of 0.05 PW.
基金the China Major State Basic Research Program (Grant No. G1999043808) the Youth Fund of National 863 Project (Grant No. 2002AA639350) the National Natural Science Foundation of China (Grant No. 49876010) and the Innovation Program of the Chinese Aca
文摘A fine-grid model (1/6) covering the South China Sea (SCS), East China Sea and Ja-pan/East Sea, which is embedded into a coarse-grid (3) global model, was established to study the SCS circulation. In the present paper, we report the model-produced monthly and annual mean transport stream functions and sea surface heights(SSH) and their anomalies of the SCS. Com-parison to the TOPEX/Poseidon data shows that the model-produced monthly sea surface height anomalies (SSHA) are in good agreement with altimeter measurements. Based on the results, the circulation of the SCS, especially the upper layer circulation, is discussed. In the surface layer, the western Philippine Sea water intrudes into the SCS through the Luzon Strait in autumn, winter and spring, but not in summer. However, as far as the whole water column is concerned, the water in-trudes into the SCS through the Luzon Strait all the year round. This indicates that in summer the water still intrudes into the SCS in the subsurface and intermediate layers. The area near the northern continental slope of the SCS is dominated by a cyclonic circulation all the year round. The SCS Southern Anticyclonic Gyre, SE Vietnam Off-Shore Current in summertime and SCS South-ern Cyclonic Gyre in wintertime are reproduced reasonably. The difference between the monthly averaged SSH and SSHA is significant, indicating the importance of the mean SSH in the SCS circulation.
