河口区潮动力的季节性变化及其机制研究

Tidal dynamics in estuaries behaves prominent seasonal variation. Except for the influence of river discharge, the seasonal variations of mean sea level and stratification also are crucial impact factors. This proposal plans to take the Changjiang Estuary as an example to, firstly acquire the seasonal variations in tidal tidal range, tidal constants and tidal asymmetry, and its spatial discrepancy by analyzing the observed long timeseries water level data and current datasets in wet and dry seasons in multiple stations, secondly apply the existing Changjiang Estuary three-dimensional numerical hydrodynamical model to reveal the key physical mechanisms for the seasonal variation of the tidal dynamics in different area of the Changjiang Estuary after adding the influence of mixed-layer height on the estimation of bottom friction and full verification, and quantitatively distinguish the contribution from the seasonal variation of river discharge, especially the contributions from mean sea level and stratification; thirdly establish ideal estuarine model with different topography (estuarine length, convergence length, tidal flat areas etc.) to obtain the characteristics of the tidal response to variations in discharge, mean sea level, and stratification in estuaries with different topography. This study can enrich the estuarine tidal theory, facilitate the understanding on the complex dynamics in coastal and estuarine areas, and promote the development and improvement of the coastal and estuarine dynamics.

河口区的潮动力具有显著的季节性变化特征。除径流量外，平均海平面和水体层化的季节性变化也是重要的影响因素。本研究拟首先以长江口为例，通过分析河口区多个站位长时间的水位观测数据和洪枯季的流速观测数据，得到长江口潮差、潮汐潮流调和常数和潮汐潮流不对称性等的季节性变化过程和特征，及这一特征在河口上下游和不同支汊中的差异性；然后改进已经拥有的长江口三维水动力数值模型，在底摩擦计算中考虑混合层高度的修正，揭示长江口不同区域潮动力季节性变化的主要物理机制，定量区分径流量，特别是平均海平面和水体层化对长江口潮动力季节性变化的贡献；最后构建不同地形（河口长度、断面缩窄速度、潮滩面积等）的理想河口模型，得到不同地形河口的潮动力对径流量、平均海平面和水体层化变化的响应特征。本研究可丰富河口潮动力理论，促进人们对河口海岸复杂动力的深入认识，推动河口海岸动力学的发展和完善。

河口区的潮动力在季节性径流量，平均海平面和水体层化的影响下，呈现显著的季节性变化特征。本研究首先搜集整理了长江口的实测潮汐数据，系统分析了长江口的潮差、分潮振幅等的季节性变化特征，然后改进已经拥有的长江口三维水动力数值模型，揭示了口外季节性层化产生河口不同区域潮动力季节性变化差异的主要物理机制。项目成果深刻认识了河口区潮动力的季节性变化机制，并应用成果为上海市风暴潮概率预报系统的建设提供理论基础，为九龙江河口-厦门湾海域的风暴淹没风险评估提供理论参考。项目的后续持续推进将进一步丰富河口海岸动力学理论，并为我国海洋防灾减灾和海洋新能源开发等工作提供理论支持。