基于波恩近似的二维浅海声层析

目前的海洋声层析方法主要针对深海环境或水平不变浅海环境,对于水平剧变的二维浅海声层析问题仍未提出实用有效的方法。提出一种二维浅海声层析方法并讨论其理论可行性。其主要的思路是将一个水平变化的浅海环境等效为一个水平不变的背景环境叠加微弱的扰动,由波动方程推导出声速扰动与格林函数扰动之间的关系式,引用波恩近似解决两者之间的非线性问题,将反演过程简化为线性方程组的求解过程;后期针对该方法的局限性做进一步改进,包括引入迭代思路及使用一定的先验知识并提取经验正交函数(Empirical Orthogonal Function,EOF)。数值仿真实验说明该方法对局部的小幅度扰动甚至是孤立子内波的反演结果都具有较高的分辨率,初步验证了该方法的理论可行性。

Two dimensional shallow ocean acoustic tomography using Born approximation

Currently most of developed ocean tomography methods aim to solve the inversion problem in Deep Ocean or the range-independent shallow water. There is still a lack of practicable methods for the strong range-dependent ocean tomography. In this paper, a two-dimensional shallow ocean acoustic tomography method is developed and the theoretic feasibility discussed. The main idea is： a range-dependent environment can be regarded as a range-independent environment with disturbance, and then the convertible formula between the sound speed profile（SSP） disturbance and Green function disturbance can be deduced from the wave equation. The nonlinear problem is solved by Born approximation so that inversion problem is transformed to a solving process of linear equations. Then the iterative way or EOF by means of observation data is introduced to improve the availability of the proposed method. Numerical simulations show that the method is capable of inverting the small amplitude disturbance of the SSP, even like soliton, with reasonable precision, and the results indicate the preliminary validation of the proposed method.