A generalized canonical sound-speed model

Abstract

A generalized canonical sound-speed (GENCASS) numerical environmental model has been developed to support range-dependent underwater acoustical propagation models, especially the PE/SSF model. The GENCASS model provides an interface between the environmental data base and acoustical model; it could guide and improve the cost effectiveness of the processes of environmental data acquisition, processing, storage, and access. It extends the usefulness of Munk's canonical model to include conditions where no subsurface axis exists, as in the arctic and subarctic, and provides for such common phenomena as mixed layers, fronts, eddies, and the double minima found in the region influenced by the Mediterranean outflow. It provides a natural parametric hierarchy for organizing environmental data, based on phenomenological time scales, ranging from climatological to seasonal to diurnal. In temperate regions, four parameters are sufficient to define the model: scale depth, bottom temperature, extrapolated surface temperature, and either actual surface temperature or mixed layer depth, which are functionally related. The GENCASS model introduces a surface thermal layer depth to account for surface superheating that may occur in tropical waters. A mixing function is introduced to account for the transition through oceanographic fronts, across eddies, and through the double minima profile. A companion paper will use the GENCASS model to support PESOGEN-II illustrative runs.