Adjusting modelled sound speed profiles for use in sonar operations

Realistic descriptions of vertical sound speed profiles are essential for modelling underwater acoustic fields. Errors in the vertical sound speed profile will have negative impact on the acoustic propagation modelling. Ocean models provides vertical profiles of temperature and salinity, from which sound speed can be derived, covering large areas with high spatiotemporal resolution. Previous experience with ocean models shows that vertical sound speed profiles are difficult to model with sufficient accuracy to be useful for acoustic modelling. A method for adjusting sound speed profiles from an ocean model to better represent measured profiles is proposed. The method is based on replacing the mean sound speed profile from the ocean model data set with mean profile of an observed data set. The method is illustrated on data from the Norwegian coast where the coastal current causes well-defined fronts and eddies. The proposed method reduces the mean root-mean-square error in the model data, particularly in the upper layers. On the other hand, comparisons of observed and modelled sound speed profiles on a one-to-one basis, is still challenging in both space and time.