【作者】 高劲松；

【导师】 赵栋梁；

【作者基本信息】 中国海洋大学 ， 物理海洋学， 2013， 博士

【摘要】 首先，基于改进的中尺度涡判别方法和海平面异常数据（SLA），本文分析了南海北部中尺度涡的变化规律及其对南海环流影响。其次，构建南海西北部的三维后报模型，分析南海环流及其它强迫因子对北部湾环流（位于南海西北部）的贡献。得到的主要结果如下：通过用相对涡度代替SLA来消除全球平均下反气旋（气旋）式涡旋对应负（正）SLA的误差，并引进流场判据消除O-W中尺度涡判别方法的误差。基于新方法的分析结果表明，南海西北部存在四个中尺度涡消散区，与南海的四个中尺度涡主要生成区相对应，从而构建四个规律性的涡旋传播通道。讨论了中尺度涡在经向上的能量通量分布，发现南海东边界和西边界是能量密集区。中尺度涡以西向传播为主，其能量通量是东向传播的6倍。与季风对海洋的输入能量相比，中尺度涡对背景流的贡献大9倍。在西向传播过程中，中尺度涡不断消失和生成，接力般把能量从南海东部传到西部，使得能量聚集在西边界。由于北部湾受南海环流影响，因此中尺度涡对南海环流的影响可以传递至北部湾。二十年来，由于有限的观测数据和大量的数值诊断计算，北部湾的季节性环流型态与生成机制一直存在较大争议。本文通过POM模式在南海西北部建立三维后报模型，模拟2006-2007年的环流变化。该模型充分考虑了日平均的风场（Blended wind data）、热通量（Woods Hool的OAFlux）以及俄勒冈大学（OSU）潮汐模型提供的六个分潮。侧边界则使用HYCOM提供的2005年12月1日到2007年12月31日的日平均温度、盐度、正压和斜压流速、水位等数据，同时考虑了气候态下几个河流的月平均径流量。模式结果与实测数据较前人最大程度的符合，不仅模拟出908专项观测到的两个上升流和两个冷水团，而且与海流观测吻合较好。基于此，本文得出与前人模型结果不一样的结论：北部湾的南部环流有显著的季节性变化特征，夏季为反气旋式环流而冬季则为气旋式，分别受南海环流和东北季风控制。北部环流则可分成东西两部分，西北部环流无明显季节性变化特征，主要受沿岸流控制，包括湾西岸的低盐水以及南部环流的分支，而东北部环流则受局地风场和琼州海峡流的共同作用。受环流影响，北部湾表层存在几个水文特征迥异的水团，包括南部高温高盐水团，西海岸和北海岸的河口羽状区形成的低盐水团以及介于二者间的混合水团，水团主要受季风、热通量以及径流量影响。无热通量时，南海的高温高盐水能够侵入北部湾更北端，混合水团和湾西岸的低盐水团往北收缩。同时湾西岸的河口羽状区受径流量和季风的共同作用，例如冬季的东北季风把低盐水压缩在近岸而夏季西南季风有助于其离岸扩展。在深层，北部湾存在两个冷水团，生成于冬季，成长于春季，在夏季和秋季不断减弱并消失。冷水团主要受热通量作用，季风起次要作用。通过把开边界设置到珠江以东以及在琼州海峡内设置足够的分辨率，提出琼州海峡流的东西向分量的日振荡分量与季节性振荡分量相当，因此在冬季和夏季的某一天也有可能是东向流或西向流。但季节性平均来讲，琼州海峡流在春末至夏末为东向，在秋季至来年春季为西向，年平均通量为西向的0.1Sv（约为）。琼州海峡流主要受海峡两端水位差控制，局地风和潮汐余流则起次要作用。本文概括分析了北部湾上升流和暖池的特征及其生成机制，包括海南岛西岸，西南岸以及越南沿岸。上升流主要存在于夏季，其中海南岛西岸上升流受潮混合和热通量控制，西南季风起反作用；越南沿岸和海南岛西南岸近岸的上升流生成机制为西南季风引起的Ekman输运。从10月到来年1月，在东北季风垂向混合和潜热通量作用下，海南岛西岸为暖池控制。在日平均和月平均的风场和热通量强迫下，北部湾的环流和水团有较大差异，例如南部环流在月平均强迫下虽然基本结构变化不大，但强度比日平均有所增强，而且北部环流的基本结构有较大改变。因此，不同时间分辨率的风场和热通量强迫对北部湾环流和水团有重要影响。本文的研究成果有助于海洋生物地球化学，海洋渔业等学科在北部湾的进一步研究，同时对广西和海南近海的海洋环境保护有重要意义。更多还原

【Abstract】 Firstly, the characteristics of eddies and their effects on the circulation in thenorthern South China Sea (SCS) were examined, basis on the Sea Level Anomalydata and developed eddy-detected method. Secondly, the three-dimensionalhindcast model was built in the northwestern SCS and the effects of SCScirculation and other factors on the circulation in the Beibu Gulf were analyzed.The findings were mainly as follows:Based on the Okubo-Weiss method, six procedures were added to avoid thenoise, which could achieve the robust results. In addition, four distinctive sinks ofthe eddy (EAAs) were firstly examined, which were linked with the four eddybirthplaces to result in four pathways for eddies in the northern SCS.The zonal distribution of the eddy kinetic energy flux (EKEF) was alsofigured out, with two peaks in the eastern and western boundary, respectively. Andthe westward EKEF was almost6times as the eastward EKEF. Compared with thework on the circulation by the wind, the work by eddies was almost night times asthat in the northern SCS. The eddy would be generated and dissipatedcontinuously along the westward propagation way. Thus, the eddy acted as a relayto transfer the energy from east to west, and the energy would be lastlyaccumulated in the western boundary.The eddy could affect the Beibu Gulf via the SCS circulation. However, thecirculation in the Gulf has not been agreed in the past twenty years, which was dueto the limited in situ data and diagnostic numerical models in the past. Therefore,the three-dimensional hindcast model was built in the northwestern SCS, modelingthe circulation in the Beibu Gulf between2006and2007. This numerical modelconsidered the daily averaged blended wind and heat flux (OAFlux Project) data,and six tidal consituents from tidal model of OSU. For the lateral boundaries, the daily averaged temperature, salinity, barotropic and baroclinic velocities, andelevation were constructed from HYCOM between December1,2005andDecember31,2007. And the monthly averaged river discharges were alsospecified. As a result, the model results were consistent with in situ data, such asthe current observation data. And two upwellings and two cold water masses weremodeled as the observation result of Project908.With the good model results, the new views were concluded: it could beshowed an apparent seasonal evolution in the southern Gulf: in summer thevertically averaged circulation was anti-cyclonic, whereas in winter the patternchanged to cyclonic. The circulation was dominated by outer SCS circulation andnortheasterly wind in summer and winter, respectively. In the northern Gulf flowswere independent between the eastern and the western side. The flows in thenorthwestern interior Gulf were affected jointly by several currents including thecoastal plume and the branch separated from the southern gyre, resulting in noapparent seasonal variation. However, the northeastern Gulf was dominated by thelocal wind and the flows from the QS.Different water masses were distinguished at the surface with the warm andsaline South China Sea water in the south, relatively fresh plume waters along thenorthern and western coasts of the Gulf, and the mixture of the two in between.They were adjusted by wind and heat flux. Such as, the warm and saline SCSwater could intrude the Beibu Gulf more northward without heat flux. In addition,the river plume in the western Gulf was modulated by the river discharge and wind,which was pushed towards the shore in winter but spread offshore in summer. Atlower levels, two cold, water masses were found in the model, which wereproduced throughout the winter, sheltered and protected from the surface warmingby a thermocline as the season progressed, and gradually disappeared fromsummer to fall. These two cold water masses were dominant by the heat flux, andwind played second role.By placing the model open boundary east of the Pearl River delta and allowing sufficient resolution of the Qiongzhou Strait (QS), flows in the QS weredetermined. Because the daily variation was at least as strong as the seasonalcurrent, flows in the QS could be westward or eastward on some days in summeror winter, but the seasonal mean current was eastward from late spring throughsummer and westward during the rest of the year, with an annual mean westwardtransport of~0.1Sv (~) into the Gulf.The characteristics and mechanisms of upwellings and warm pool wereexamined in the Beibu Gulf. The upwelling off western coast of Hainan wasdominated by tidal mixing and heat flux, while the southwesterly wind hadnegative effect on it; the upwellings off Vietnamese coast and off southern coast ofHainan were induced by the Ekman transport of southwesterly wind. In addition,there was warm pool existing between October and January off the western coastof Hainan, induced by the latent heat flux and vertical mixing by the northesterlywind.Basis on this work, the research of marine biogeochemistry and fishery willbe carried out. In addition, it is helpful to the protection of marine environment offcoasts of Guangxi and Hainan.更多还原