Numerical Similation Of The China Adjacent Sea Circulation And Its Seasonal Variation

A variable-grid global ocean circulation model whose horizontal resolution is fine (1/6() in the South China Sea (SCS), East China Seas and Japan/East Sea, and coarse (3() in the rest part of the world ocean, was established based on GFDL's MOM2 to study the ocean circulation of the China adjacent sea and its seasonal variation.Base on the model results, the monthly and annual mean freshwater, heat and salt transports through the open boundaries of the South and East China Seas are reported. 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 transports of 5.3 Sv, 0.57 PW and 184Ggs-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 transports of the Kuroshio in the East China Sea are 25.6Sv, 2.32 PW and 894Ggs-1, respectively. Less than 1/4 of those transports pass 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. The mean sea surface heights (sea surface dynamic topography) of the South China, East China, Yellow and Bohai Seas are derived from the model results and surface air pressure. The result shows that the China 1985 National Altitude Datum is 24.7cm above the mean sea surface height of the world ocean. The mean sea surface in the coastal ocean adjacent to China is higher in the south than in the north. Comparison of the model results with the geodetic leveling measurements at 28 coastal tidal stations shows a standard deviation of 4.8cm and a fitting coefficient of 95.3%. After correction through linear regression, the standard deviation is reduced to 4.5cm. This indicates that the accuracy of model results is sufficient for practical application. Based on the model results, the mean sea surface heights for the study area with a resolution of 1/6 degree are given. This result also links the mean sea levels at islands with those on the mainland coast and gives the mean sea surface heights at tidal stations in Taiwan, Dongsha, Xisha and Nansha relative to the China 1985 National Altitude Datum.The model-produced monthly and annual mean transport stream functions and sea surface heights(SSH) and their anomalies,and isopycnal-surface circulation of the SCS are reported. Comparison 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 is discussed. In the surface layer, the western Philippine Sea water intrudes 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 intrudes 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 Southern Cyclonic Gyre in wintertime are reproduced reasonably well. The difference between the monthly averaged SSH and SSHA is significant, indicating the importance of the mean SSH in the SCS circulation. Based on the model-produced isopycnal-surface circulation, subsurface and intermediate circulations have remarkable seasonal variations. Subsurface water intrudes the SCS through Luzon Strait all the year round, with the strongest intrusion in winter and the weakest in summer. Intermediate circulation patterns significantly differ from the upper layer circulation. In summer, intermediate...