Influence of anisotropic smoothing of the input sound speed fields computed from submesoscale permitting ocean models on the resulting stability of simulated eigenrays

Time-varying range-dependent sound speed profiles (SSPs) computed from high-resolution submesoscale-permitting ocean models can exhibit strong lateral and vertical gradients which are numerically challenging for standard ray-tracing methods, especially in complex environments with abrupt topography. These strong SSPs gradients affect the stability of the predicted eigenrays, e.g., yielding spurious ray arrivals intermittently. Here an anisotropic smoothing kernel, with tailored kernel sizes in the vertical and horizontal dimensions, is applied to the simulated SSPs to enhance the stability of predicted eigenray from standard ray-tracing while retaining the underlying dynamics of the original SSPs. The arrival-times predicted from these smoothed ray tracing simulations—for frequency <1 kHz—match those obtained from parabolic equation (PE) simulations used as benchmark. Furthermore, the predicted arrival-times from PE simulations are found to remain unaffected whether the anisotropic smoothing procedure is applied to the input high-resolution SSPs, as expected since frequency-dependent diffraction effects captured by PE inherently apply a smoothing effect to the SSP gradients. Hence using this smoothing procedure allows to retain the computational efficiency of ray tracing in complex environments while ensuring accurate arrival-time predictions comparable to results from more stable but significantly more computationally intensive PE simulations, [Work supported by ONR.]