台风-潮流-波浪耦合的风暴潮预报模型研究

Storm surge disaster has become primary marine disaster in China. It’s of considerable realistic significance to improve the prediction accuracy of storm surge forecast model effectively for enhancing disasters prevention and mitigation and ensuring urban flood control and safety. Based on an existing storm surge numerical model, the Simulating Waves Nearshore model (SWAN) and the Weather Research and Forecasting Model (WRF), a coupled typhoon-tidal current-wave interaction model system is going to be established to forecast the storm surge. Firstly, The variational assimilation technique is introduced into the high-resolution numerical weather prediction WRF model. The typhoon forecast accuracy can be improved at different time periods and providing more accurate wind fields for the storm surge model according to different timeless and accuracy of data. Secondly, a coupled wave-current interaction model is going to be developed to identify the tidal surge-wave interaction. Thirdly, the coefficient of wind drag force is going to be optimized by the variational assimilation model, which could further improve the prediction accuracy of the model. Finally the comprehensive storm surge forecast model coupling typhoon, tidal current and wave is going to be established based on the precision weather model and could provide a decision-making basis for the warning emergency system of urban flood prevention.

风暴潮灾害现已成我国首要的海洋灾害，如何有效地提高风暴潮预报模型的预报精度，对防灾减灾，确保城市的防汛安全具有非常重要的现实意义。本项目拟利用自主研发的台风风暴潮模型与天气预报模型WRF及波浪模型SWAN相耦合，构建风、浪、流耦合模型。对高分辨率数值天气预报WRF模型引入变分同化技术，使程序能根据数据不同的时效性和精度，分时段提高台风预报的精度，从而更有效地为风暴潮模型提供准确风场输入；构建浪流耦合模型，研究波、流的相互作用，确定波致辐射应力场与潮流场之间的直接平滑循环反馈的方法；通过研究风拖曳力系数变分同化技术，建立与浪流耦合模型自动融合的风拖曳力系数变分同化模型，以消除人为误差、使模型分析与预测达到最优化。最终基于高精度天气模型构建风、浪、流耦合的风暴潮预报模型，为城市防汛预警应急工作提供决策依据。

随着全球气候变化以及海洋开发利用的进一步深入，风暴潮灾害的频发程度和危害程度呈现上升趋势。利用数值模拟提供准确的风暴潮预警预报信息是防灾减灾、保障防汛安全的关键。虽然目前国内外诸多学者进行了大量的风暴潮数值模拟研究工作，却极少考虑台风预报的不确定性对风暴潮预报的影响，而且大多数未全面深入地考虑波浪与风暴潮之间的相互作用。. 本项目利用高适用性的有限体积法自主构建了高分辨率的风暴潮模型。以提高风暴潮预报精度为目标开展了较全面的研究工作。首先，针对风暴潮驱动风场预报准确性问题，通过WRF数值试验研究提出合适的网格嵌套方式及控制条件，并通过三维变分同化为风暴潮模型提供更准确的台风驱动风场。其次，研究波浪引起的表面风应力、辐射应力以及底应力与风暴潮的相互影响，构建了充分考虑波流相互作用的台风-潮流-波浪耦合模型。最后，利用四维变分同化方法构建代价函数和伴随方程对风拖曳力系数进行优化。研究结果表明，构建的台风-潮流-波浪耦合模型能有效提高风暴潮的预报精度。鉴于预报的台风参数存在较大不确定性，本项目构建了适用于业务预报的多工况集合预报模式，为城市减灾和海岸防护提供更有效的参考，具有较高的实用价值和重要的现实意义。