风暴过程中浅水风应力拖曳系数变化机理研究

The mechanism of the change of the stress drag coefficient during the storm is always a hot and difficult topic. At present, the research of ocean surface wind stress drag coefficient are basically based on the observation data in the deep water area or the deep water wave theory. The wind stress drag coefficient in shallow water is different from that in deep water. They are used in the wave numerical model, and the deviation of offshore wave calculation results is too large. In addition, the mechanism of drag coefficient reduction under high wind speed is still insufficient, and the related research in shallow water area is rarely involved too. On the basis of previous studies, this project intends to systematically study the variation characteristics of the wind stress drag coefficient in shallow water under the storm process by means of theoretical research, numerical simulation, field observation and data analysis, and compare the results with those in deep water. At the same time, the data of wave, wind speed and water depth measured simultaneously are used to reveal the mechanism of different factors, especially water depth and wave steepness, on the wind stress drag coefficient in shallow water during the storm, and finally a more reasonable parameterized model of wind stress drag coefficient is established and developed. This study will help to improve the prediction accurate of wave models, and it is also very important for the disaster prevention and mitigation of our country.

风暴过程中风应力拖曳系数变化机理一直是研究的热点和难点。现有风应力拖曳系数变化研究基本都是基于深水区观测资料或者深水波理论获得的，而研究认为，深水区风应力拖曳系数不同于浅水区，直接利用深水区风应力拖曳系数参数化模型计算近岸波浪会造成所得结果与实际值偏差过大，此外，高风速下风应力拖曳系数变小机理研究还存在不足，浅水区域相关研究更是少有涉及。本项目拟在以往研究基础上，采用理论研究、数值模拟、现场观测和资料分析等方法，系统研究风暴过程中风应力拖曳系数在浅水下的变化特征，并与深水区研究结果进行对比；同时利用同步测量的波浪、风速、水深等数据，揭示风暴过程中不同要素尤其是水深和波陡对浅水风应力拖曳系数的作用机理，最后建立和发展更为合理的风应力拖曳系数参数化模型。该研究有利于提高风暴波浪数值模式的预报精度，对我国近海防灾减灾工作意义重大。

风暴过程中风应力拖曳系数变化机理一直是研究的热点和难点。现有风应力拖曳系数变化研究基本都是基于深水区观测资料或者深水波理论获得的，此外，高风速下风应力拖曳系数变小机理研究还存在不足，浅水区域相关研究更是少有涉及。本项目在以往研究基础上，系统研究风暴过程中风应力拖曳系数在浅水下的变化特征，揭示了风暴过程中不同要素对浅水风应力拖曳系数的作用机理，最后建立和发展更为合理的风应力拖曳系数参数化模型。本项目采集和收集了山东近海区域的流速（定点）、波浪（座底）和风速观测资料，其中获取流速数据14组，波浪数据2年，风速数据14组；利用数值模型，初步探索了台风“利奇马”过程中台风浪的空间分布特征，尤其是在近海区域的变化特征，为山东省开展台风浪预警及防灾减灾提供技术支撑；利用理论分析、数值模型等手段，给出了适用于不同风速条件下的拖曳系数参数化模型，有效提高了浅水区域条件下的风暴波浪模拟能力。研究发现：在极端风况和海况条件下，ERA5风和波浪数据出现低估的现象；在中低风速下飞沫对拖曳系数的影响可以忽略不计，无量纲的海面粗糙长度先随着波龄的增加而增加，继而随波龄的增加而减小；然而在高风速下，因气泡破裂或者波浪破碎产生的飞沫使得风廓线对数函数改变，造成拖曳系数的减小。对不同波龄而言，拖曳系数和粗糙长度达到最大值的风速并不相同。研究取得了良好的科研成果，超额完成了项目拟定的各项任务指标：发表学术论文16篇，培养研究生1名，参加国内外会议4次，获批省部级以上的纵向项目1项（55万）、横向项目6项（¥240万元）。