Numerical Study On The Temporal And Spatial Variability Of The Elements Of The South China Sea Circulation

The area of the South China Sea is wide and then the high temporal and spatial observation of the ocean current is difficult; therefore experts study the circulation of the South China Sea using three-dimensional numerical models. The models, the resolution, the depths, the boundaries, the forcing fields are different; so the simulation results are of obvious difference. My work simulates the circulation of the South China Sea using Hybrid Coordinate Ocean Model whose resolution is high, base on nested scheme. The sea surface temperature (SST) is the key indicator of the ocean surface thermal condition and the sea surface temperature of the South China Sea is always the key of the observation, the study and the forecast. The sea surface height (SSH) gives an image of the dynamic structure of the upper ocean circulation; therefore the study of the sea surface height is one of the key issues about the upper ocean circulation. Some consensus of the temporal and spatial variability of the sea surface temperature and the sea surface height anomalies have been obtained by observing and modeling. On the one hand, the simulation results have been verified by the consensus. On the other hand, the controversies of the temporal and spatial variability of the sea surface temperature and the sea surface height anomalies can be further studied. By analyzing the temporal and spatial variability of the sea surface temperature of the South China Sea and contrasting the results with others, the variance contribution rate and spatial patterns of the model results are similar to those of the remote sensing data. Furthermore, the time variation of the time coefficient series of the second and the third mode has been analyzed using wavelet analysis and the second mode and the third mode all have half annual variability; however, the annual variability between the modes is significantly different. The temporal and spatial variability of the sea surface height anomalies of the South China Sea from the model results and the SSALTO/DUACS MSLA data which assembles sets of the remote sensing data are analyzed and then are contrasted with others. The first mode, whose variance contribution rate is governing, mainly reflects the effect of the monsoon; the results of the second mode are different largely; the third mode and the fifth mode reflect the effect of the upwelling along the coast of Vietnam; the fourth mode reflects the dipole pattern. Furthermore, the time variation of the time coefficient series has been analyzed using wavelet analysis. The first three modes have typical annual variability; the periodic signal of the fourth mode is different largely, the fifth mode mainly has half annual variability. The analysis of the temporal and spatial variability of the sea surface temperature and the sea surface height focuses on the study of the upper circulation of the South China Sea; therefore the representative Luzon strait has been selected to analyze the feature of the vertical circulation of the South China Sea. Previous studies of the water exchange of the Luzon strait only involved in one section because of the limitation of the observation and the section was selected differently. Because the water moves continuously in space, only one section can not reflect the continuity. My work selects multiple sections in the vicinity of the Luzon strait which represents different sea areas, namely the water exchange area of the Luzon strait, the northern South China Sea and the Kuroshio. By analyzing the flow of the sections and the seasonal and annual changes of the water exchange, the water exchange through different sections which represent the different sea area, such as the 120.5°E section represents the Luzon strait; the 119.5°E section represents the northern South China Sea and the 121.5°E section represents the Kuroshio, is different largely. By analyzing the water exchange of the different layer, the seasonal and annual changes of the water exchange between upper layer and lower layer are also different largely. Finally, the seasonal and annual changes of the input and output are also different largely.