Duda Timothy F, Lin Ying-Tsong, Newhall Arthur E, Helfrich Karl R, Lynch James F, Zhang Weifeng Gordon, Lermusiaux Pierre F J, Wilkin John
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02559, USA.
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Acoust Soc Am. 2019 Sep;146(3):1996. doi: 10.1121/1.5126012.
Three-dimensional (3D) underwater sound field computations have been used for a few decades to understand sound propagation effects above sloped seabeds and in areas with strong 3D temperature and salinity variations. For an approximate simulation of effects in nature, the necessary 3D sound-speed field can be made from snapshots of temperature and salinity from an operational data-driven regional ocean model. However, these models invariably have resolution constraints and physics approximations that exclude features that can have strong effects on acoustics, example features being strong submesoscale fronts and nonhydrostatic nonlinear internal waves (NNIWs). Here, work to predict NNIW fields to improve 3D acoustic forecasts using an NNIW model nested in a tide-inclusive data-assimilating regional model is reported. The work was initiated under the Integrated Ocean Dynamics and Acoustics project. The project investigated ocean dynamical processes that affect important details of sound-propagation, with a focus on those with strong intermittency (high kurtosis) that are challenging to predict deterministically. Strong internal tides and NNIW are two such phenomena, with the former being precursors to NNIW, often feeding energy to them. Successful aspects of the modeling are reported along with weaknesses and unresolved issues identified in the course of the work.
几十年来，三维（3D）水下声场计算一直被用于了解倾斜海床上方以及三维温度和盐度变化强烈区域的声音传播效应。为了近似模拟自然环境中的效应，可以根据一个由业务数据驱动的区域海洋模型的温度和盐度快照来生成所需的三维声速场。然而，这些模型总是存在分辨率限制和物理近似，会排除一些可能对声学有强烈影响的特征，例如强烈的亚中尺度锋面和非静力非线性内波（NNIW）。在此，报告了一项利用嵌套在包含潮汐的数据同化区域模型中的NNIW模型来预测NNIW场以改进三维声学预报的工作。这项工作是在综合海洋动力学与声学项目下启动的。该项目研究了影响声音传播重要细节的海洋动力过程，重点关注那些具有强烈间歇性（高峰度）且难以确定性预测的过程。强烈的内潮和NNIW就是这样两种现象，前者是NNIW的先兆，常常为其提供能量。报告了建模工作的成功之处以及在工作过程中发现的弱点和未解决的问题。
