沿海声层析观测能够用较少的仪器进行海域内部大范围的长期同步观测，具有潜在的优势和应用前景。项目组通过前期努力，已基本把沿海声层析技术引进到了我国，实现了沿海声层析技术在我国的初步应用。本项目主要目标是要把沿海声层析观测数据同化到适合近海的非结构网格海洋数值模式（FVCOM）中去。主要研究内容有：根据声线和三角网格的空间关系，建立三角网格坐标下的声传播模式，进而建立双向传播时间差与模式流速状态向量在非结构三角网格中精确的投影算子，实现声学观测数据到流场的转换；在此基础上利用集合卡尔曼滤波方法将沿海声层析观测得到的声传播时间差数据同化到FVCOM中。利用我国沿海典型海区的海上验证实验资料，通过与常规观测仪器观测结果的比较，分析误差，改进同化模式，确立同化模式的可信性。本项目的最终目标是建立和完善适合我国沿海的声层析同化模式，为我国沿海海洋动力环境的预测预报和海洋科学研究提供必要的技术支撑。

Coastal Acoustic Tomography (CAT) can obtain large-scale, long-term synchronous observations of the ocean’s interior, using only a few instruments, and thus has considerable advantages over other methods, and potentially wide applications. The project team has introduced the technique of CAT to China, and utilized it there for the first time. The aim of this project is to assimilate the CAT observational data into the Finite-Volume Community Ocean Model (FVCOM), which is a numerical model based on unstructured grids, and is applicable to coastal regions. The research primarily consists of : (1) constructing a sound transmission model, based on the spatial relationship of sound transmission lines within a triangular grid coordinate system; then (2) determining the precise projector in the unstructured triangular grid from the reciprocal travel time difference to velocity status vector, thus achieving the conversion from acoustic observational data to current field data; and (3) utilizing an ensemble Kalman filter technique to assimilate the observed travel time difference data from CAT into the FVCOM model. We will use observational data from some typical coastal regions of China to verify our results. By comparing the model results with observations obtained using common techniques, and then analyzing the model errors, we will modify the assimilation model and verify its reliability. The final aim of this project is to establish a CAT assimilation model suitable for the coastal current fields in China, which will provide the necessary technological support for coastal dynamical environment forecasts in China, facilitating marine science research.