Sensitivity of sound speed fluctuation on acoustic arrival delay of middle range in deep water

For middle range acoustic propagation in deep water, there exists mainly four types of ray arrivals, namely direct path arrival, one time surface-reflected (SR) arrival, one time bottom-reflected (BR) arrival and one time surface-reflected bottom-reflected (SRBR) arrival. With Bellhop ray model, sensitivity of sound speed fluctuation on the arrival delay of middle range in deep water was studied. Argo profiles in Philippine Sea were used to establish the Sound Speed Profile (SSP) fluctuation set with the Empirical Orthogonal Function (EOF) method. Numerical simulation suggests that when the source was closer to the sea surface, the relative delay structure was more sensitive to the SSP fluctuation, and that the SR arrival and the SRBR arrival were more sensitive to the fluctuation than the BR arrival. When receiver range increases from 20 km to 30 km, sensitivities of ray arrivals gradually increase. Acoustic arrival delay data in the Philippine Sea experiment was used to invert the SSP. The inverted result agrees with the measured data well, suggesting the arrival structure was a nice choice for acoustic tomography of middle range in deep water.