珠江口冲淡水扩展变化及机制研究

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	珠江口冲淡水扩展变化及机制研究
其他题名	A study on the variations and mechanisms of the PRE plume
	欧素英
学位类型	博士
	2005-11-29
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	珠江口南海北部陆架冲淡水羽扩展径流潮汐风沿岸流
摘要	本文利用1978~1984年南海北部的逐月调查资料，分析珠江口冲淡水的扩展特征及其扩展变化。资料分析显示，在风及入海径流量等因素的影响下，珠江口冲淡水的扩展具有季节变化和年际变化。夏季珠江口冲淡水在河口外的扩展形态可划分出四种扩展形态，包括向海扩展型、粤东扩展型、粤西扩展型及似对称扩展型。同时根据珠江入海月平均流量与冲淡水扩展面积的相关分析可知，珠江口入海流量的大小决定了河口冲淡水在口外的扩展大小，流量的季节变化决定了冲淡水扩展大小的季节变化，而流量的年变化影响着冲淡水扩展的年变化。根据海域风场与冲淡水扩展形态的对比分析表明，风的季节变化和日变化影响着冲淡水扩展方向的变化，风场影响控制了珠江口冲淡水不同的扩展形态。夏季在E~SE向风的作用下，珠江口冲淡水扩展表现为粤西扩展型；而珠江口冲淡水扩展为粤东扩展型时，南海北部的月平均风场为SSW~SW向风。冲淡水扩展倾向于向海扩展型时，海域吹S风为主，且风速较小。在资料分析的基础上，本文利用ECOM模式对冲淡水扩展的动力机制进行进一步探讨。模式试验结果表明，理想情况下，珠江河口冲淡水向外海突出，冲淡水扩展形态为向海扩展型；珠江入海流量的大小决定冲淡水扩展范围的大小，入海流量大，冲淡水扩展的范围大。不同方向的盛行风是珠江河口冲淡水扩展形态和动力的决定因子。在东北风、东风和东南风的作用下，河口冲淡水形态为粤西扩展型，风持续时间长，冲淡水扩展形态表现为极端粤西扩展型。在西南季风的影响下，河口冲淡水的扩展方向明显相反，冲淡水扩展形态表现为典型的粤东向离岸扩展型。S、SSE风约束了河口冲淡水向口外的扩展，冲淡水扩展形态表现为轻微的粤东向扩展。在偏E风与偏S风交替作用下，表层冲淡水在一定时刻会出现似对称形态。在对南海北部潮汐潮流研究的基础上，本文进一步模拟了潮汐潮流对珠江口冲淡水扩展的影响。模型试验结果显示，珠江口周期性的潮流运动所造成的低盐水的净水平输运很小，其主要作用更多体现在对冲淡水与周围高盐水体的混合上，在很大程度上限制了低盐水向海或向两侧方向的扩展。在模型试验的基础上，本文进一步模拟了在多种动力因子作用下夏季珠江口冲淡水的扩展演化规律。模式计算表明，珠江口冲淡水扩展形态的演变受多种因素影响，而风是其中影响冲淡水扩展演化最重要的因子。将考虑斜压效应和不考虑斜压效应的模式计算结果进行比较，结果显示珠江口冲淡水扩展对粤东、粤西沿岸流的形成和发育影响明显。夏季珠江口冲淡水的扩展可促进粤东沿岸流的进一步发育，粤东沿岸流强化。而影响粤西沿岸流的主要因子是风应力和珠江口冲淡水的西向扩展，无风或弱风时，粤西西向流主要是由于冲淡水与周围水体的压力差所产生的密度流经过地转调整作用形成的；否则是SE~NE风与珠江口冲淡水的西向扩展同时影响粤西沿岸流的西向流动。
其他摘要	Data of 1978~1984 years were used to analyze the characteristics and variations of the Pearl River buoyant plume. The results show that the spreading of the Pearl River plume exhibits tidal period, seasonal and annual variations under dynamic factors such as wind, tide and river discharge. The plume shapes vary gradually and can be divided into four types: According to the horizontal plume morphology, the buoyant plume formed in summer can be classified into four types: Offshore Bugle Spreading (Type I) which the Pearl River plume moves off the mouth to the south, West Alongshore Spreading (Type II) which the Pearl River plume moves along the coast to the west, East Offshore Spreading (Type III) which the Pearl River plume moves off the coast to the east, Western and Eastern Alongshore Spreading (Type IV) which the Pearl River plume moves along the coast to the east and the west. Correlation analysis between month average discharge of the Pearl River and the buoyant plume sizes were carried out, and it can be concluded that the magnitude of the Pearl River discharge determines the plume size, which the seasonal, annual variations of river discharge lead to corresponding variations of the PRE buoyant plume. The correlation between plume shapes and the dominant winds show that the wind seasonal and dairy changes controll the expanding direction and the plume forms. Type II buoyant plumes in summer is related to the E~ SE wind, and Type III plume relates to SSW~SW wind. Type I relates to S wind and wind velocity is small, but Type IV buoyant plume formed by alternative winds. Based on data analysis, the dynamics of the PRE plume were studied deeply by ECOM model. The result of numerical experiments shows that, under idealized circumstance which take no account of the wind and tide, the Pearl River plume spread outwardly, and the expanding form exhibits Type I. The result of model test also shows that the river discharge determines the PRE plume extent. With the analysis of ECOM model tests about wind influences, it is known that wind is the predominant factor to control the plume forms and related dynamical process of the Pearl River plume. Under NE ~ SE wind, Type II buoyant plumes formed. Under SW wind, the spreading direction moves to east off coastal sea and the form exhibits Type III. S wind and SSE wind hold back seaward spreading of brackish water and the Pearl River plume expand to east. The spreading form inclines to Type IV buoyant plume at some time under deflected E with S wind. On the base of tide and tidal current of the SCS northern, the effect of tide and tidal current on the PRE plume was studied. The result of model experiment shows that net horizontal transport of brackish water induced by the periodic tidal current is very small, and the influences of tidal current on the mixing is significant and, to some degree, hold back seaward expanding of the PRE plume. The evolutions of the PRE buoyant plume was summaried and modeled under real tide, three days average wind and diary average river discharge. The result of numerical simulation shows that the plume moves from west to east along coastal sea and wind is the dominant factor to affect the evolution of the plume. Compared baroclinic numerical simulations with no baroclinic simulations, it is known that the spreading of the Pearl River plume plays an important role in the formation and evolution of Guangdong long-shore current. In summer it promotes the development of Yuedong littoral current and the littoral current intensified notably. The winds and the westward spreading of the Pearl River plume all contribute to the development of westward littoral current. If wind velocity is very small, the westward littoral current is formed by density current caused by the pressure difference between brackish water and surrounding water, which adjusted by earth rotation. Otherwise it is induced by SE~NE winds and the westward spreading of the Pearl River plume.
页数	148
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/205
专题	实验海洋生物学重点实验室
推荐引用方式 GB/T 7714	欧素英. 珠江口冲淡水扩展变化及机制研究[D]. 海洋研究所. 中国科学院海洋研究所,2005.

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