沿岸上升流和河流沖淡水都會嚴重影響近岸水體的物理、化學性質及其生態系統；南海北部的廣東沿岸同時存在著這兩種現象，因此對於沿岸上升流和沖淡水的運動規律和動力機制的研究對於認識廣東沿岸水體性質和生態環境的變化具有重要的理論意義。本文首先利用多種衛星遙感觀測資料和實地調查資料研究珠江沖淡水和紅海灣內的上升流進而揭示其空間分佈特徵和時間變化規律。而後利用三維的高解析度區域海洋模式（ROMS）建立一個適用於南海北部的海洋動力模式，從而成功反演珠江沖淡水和紅海灣內上升流的發展變化規律，進而揭示對其產生影響的動力原因。 / 通過分析MODIS在2003年7月14日至16日的海表面溫度影像以及同一時期的QuikSCAT風場資料，本文發現在西南風盛行時紅海灣記憶體在一個明顯的上升流區域，而且湧升的冷水首先在紅海灣的西岸出現並呈尖形向東南輸送。通過MODIS衛星觀測的海表面28oC等溫度線和模式類比結果的相互印證，證明本文利用ROMS建立的上升流模式能夠成功再現上升流的發展變化過程。基於模式類比結果的動量平衡分析揭示沿岸方向的壓強梯度和非線性項導致湧升的冷水首先出現在紅海灣西岸，而冷水的楔形離岸輸運則是由東南風引起的Ekman輸運和水準的非線性共同作用的結果。本文還進一步討論了季風、潮汐和海底地形對上升流的產生和擴散過程的影響。模式類比結果表明：在紅海灣觀測到的海表冷水是由西南風驅動的上升流造成的；由海底地形引起的內潮和上升流之間的相互作用會增強底層水的上升運動；湧升冷水的離岸輸運距離受海底地形在垂直於岸線方向的影響：坡度較緩的海底有助於冷水在距離海岸較寬的區域湧升至水面，而坡度陡的海底會將上升流限制在距離海岸較近的區域。 / 珠江沖淡水是本文的另外一個研究重點。通過對2012年6月4日-14日在珠江口和鄰近海域的調查資料的分析，可以看出調查期間珠江沖淡水呈現兩種截然不同的分佈特徵。利用ROMS的嵌套技術，本文建立了一個覆蓋南海北部陸架區的小區域模式。通過與實測資料的對比，驗證了本文建立的區域模式可以很好的反演珠江沖淡水在不同風場作用下的空間分佈特徵。基於模式類比結果的動量平衡分析表明，除了由風引起的海表面Ekman輸運外，非線性对流项項是另外一個影響沖淡水離岸輸運距離的重要因素。 / 通過計算不同風場作用下不同潮時的Froude數發現，在東南風和大潮共同作用下，珠江口鋒面處於超臨界狀態。這與實際調查結果相符合。進一步對潮汐羽流的分析表明，在東南風盛行時，珠江沖淡水由潮汐羽流、再迴圈羽流和羽流沿岸流三部分組成。當盛行風向轉為西南風時，再迴圈羽流部分消失。此時，珠江沖淡水羽流只由潮汐羽流、羽流遠場兩部分組成。計算海表面水準方向上的鹽量輸運發現，鹽量輸運受風場和潮汐的共同作用影響，潮汐導致的表層負鹽度通量可達到風生平均流引起表層負鹽度通量的12.5%。風場影響著沖淡水區域的垂向層化強度和離岸輸運距離。東南風和大潮的共同作用下，水體垂向混合加強，沖淡水離岸輸運距離變短。而盛行西南風時，強密度躍層將表層風引起的混合與底層混合隔開，有助於層化的建立，此時表層沖淡水離岸輸運距離增加。 / The upwelling event that occurred in Guangdong coastal water during 14-16 July, 2003 is observed by using satellite multi-sensor data including the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) and QuikSCAT ocean surface winds. Successive MODIS SST images reveal a jet-like upwelling cold water body in surface layer under the forcing of southwesterly winds. The ROMS is used to simulate the upwelling process and explore its dynamics. The model successfully reproduces the jet-like shape of the surface upwelling water as well as the upwelling-developing process by comparisons of 28°C isotherms between the modeling and MODIS SSTs. Analyses of modeled momentums reveal that the large offshore transport appeared on the west side of Honghai Bay as results of high alongshore pressure gradient and nonlinear advections, and in addition to the offshore-ward Ekman transport generated by the southwesterly winds, the enhanced horizontal advection also played an important role in developing the prominent upwelling in Honghai Bay. / As testified by a numerical experiment, it is the wind-driven upwelling not the wind-induced vertical turbulent mixing that induced the surface cold water. Further numerical analyses reveal strong internal tides occurring in Honghai Bay caused by the local bottom topography. The interaction between the upwelling and internal tides enhances the bottom water uplifting. The offshore expansion of the upwelling water is controlled by the cross-shore topography slope: a gentle and offshore-extended slope helps the bottom water to climb up to the surface in a wide range in cross-shore direction, whereas a steep and narrow slope restricts the expansion of the upwelling water and confines the cold water in a narrow band along the shore. / A sea cruise was carried out to capture Pearl River plume structure in the Pearl River Estuary (PRE) and its adjacent coastal waters from 4 June to 14 June, 2012. The cruise data are analyzed to unveil the plume dynamics. A nested model is used to simulate the plume expansion process as well. Model results are compared with cruise observations and tidal gauge sea level data. Modeling results suggest that there is a sub-tidal, anti-cyclonic bulge on the west side out of the river mouth under southeasterly winds, which constitutes a plume re-circulating. When the wind changes to the southwesterly, however, the plume re-circulating vanishes and a plume far-field appears. / The distinct, supercritical plume front occurs with southeasterly winds prevailing in spring tide. The tidal salt deficit flux can reach as high as 12.5% of the mean current flux, and indicates an interaction between the wind forcing and tides. The variation of plume stratification is studied by a scalar parameter. It is found that the stratification of the plume is sensitive to the wind forcing: The southeasterly winds can enhance vertical mixing in the whole water column and restrict seaward expansion of the plume water. Under the southwesterly winds, the strong stratification acts as a barrier separating wind-induced surface vertical mixing and bottom mixing. The plume water in the surface layer maintains its stratification and spreads horizontally. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Gu, Yanzhen. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 137-148). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / ABSTRACT --- p.I / 摘要 --- p.IV / CONTENTS --- p.VI / List of Tables --- p.VIII / List of Figures --- p.VIII / Acknowledgments --- p.XII / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- General Circulation in the Northern SCS --- p.6 / Chapter 1.1.1 --- Dongsha Current --- p.6 / Chapter 1.1.2 --- SCS Warm Current --- p.7 / Chapter 1.1.3 --- Other Features --- p.8 / Chapter 1.2 --- Coastal Upwelling --- p.8 / Chapter 1.2.1 --- Wind-induced Coastal Upwelling --- p.8 / Chapter 1.2.2 --- Overview of Coastal Upwelling Studies --- p.9 / Chapter 1.3 --- The Pearl River Plume --- p.12 / Chapter 1.3.1 --- Physical Setting --- p.12 / Chapter 1.3.2 --- Overview of River Plume Studies --- p.15 / Chapter 2 --- Regional Ocean Model System --- p.18 / Chapter 2.1 --- Equation of Motion --- p.19 / Chapter 2.2 --- Model Time-Stepping Scheme --- p.20 / Chapter 2.3 --- Boundary Conditions --- p.21 / Chapter 2.4 --- Coordinate System Transformation --- p.22 / Chapter 2.5 --- Vertical Viscosity and Diffusion --- p.26 / Chapter 3 --- Dynamical Study of Coastal Upwelling --- p.27 / Chapter 3.1 --- Satellite Data --- p.27 / Chapter 3.2 --- Data Interpretation --- p.28 / Chapter 3.2.1 --- Upwelling and Wind Fields --- p.28 / Chapter 3.2.2 --- Horizontal Structure and Expansion of the Cold Water Area --- p.33 / Chapter 3.3 --- Model Configuration --- p.34 / Chapter 3.4 --- Model Results --- p.38 / Chapter 3.4.1 --- Sea Surface Temperature and Horizontal Currents --- p.38 / Chapter 3.4.2 --- Cross-shelf Structure --- p.44 / Chapter 3.4.3 --- Momentum Balance --- p.46 / Chapter 3.5 --- Discussions --- p.50 / Chapter 3.5.1 --- Winds --- p.50 / Chapter 3.5.2 --- Internal Tides --- p.53 / Chapter 3.5.3 --- Topography --- p.56 / Chapter 4 --- Dynamical Study of the Pearl River Plume --- p.63 / Chapter 4.1 --- Cruise Observations --- p.63 / Chapter 4.2 --- Data Interpretation --- p.66 / Chapter 4.2.1 --- Observed Surface Salinity Distribution --- p.66 / Chapter 4.2.2 --- Salinity Vertical Distribution --- p.68 / Chapter 4.2.3 --- River Plume Front --- p.74 / Chapter 4.3 --- Model Configuration --- p.76 / Chapter 4.3.1 --- Northern South China Sea Model --- p.78 / Chapter 4.3.2 --- Pearl River Estuary Model --- p.79 / Chapter 4.4 --- Model Results and Verification --- p.80 / Chapter 4.4.1 --- Validation of Surface Salinity --- p.80 / Chapter 4.4.2 --- Validation of Salinity Profile --- p.82 / Chapter 4.4.3 --- Validation of Tidal Elevations --- p.83 / Chapter 4.4.4 --- Plume Horizontal Structure --- p.87 / Chapter 4.4.5 --- Plume Cross-shelf Structure --- p.91 / Chapter 4.4.6 --- Momentum Balance --- p.95 / Chapter 4.5 --- Stratification --- p.101 / Chapter 4.6 --- Plume frontal Froude number --- p.106 / Chapter 4.7 --- Tidal Plume --- p.111 / Chapter 4.8 --- Horizontal salt deficit flux --- p.114 / Chapter 4.9 --- Turbulence Mixing --- p.118 / Chapter 5 --- Conclusions --- p.124 / Chapter Appendix I: --- List of Publications during Ph. D. Study --- p.128 / Chapter Appendix II: --- MODIS SST Image --- p.129 / Reference --- p.137