Hierarchical clustering of historic sound speed profiles

Categorizing historical sound speed profiles stems from the desire to map spatial and temporal variability. Sound speed variability correlates with environmental phenomena and is an indicator of changes in sonar performance. Sound speed maps will assist in planning more efficient environmental survey operations such as conductivity, temperature, depth (CTD) collections. Intrinsic profile attributes estimated directly from the profile, such as the mean, variance, and derivative values, are used in the clustering process separately or in conjunction with extrinsic attributes such as location and ocean floor depth. Examples are used to demonstrate that the underlying spatial boundaries of the cluster groupings identify regions where sound speed profiles are consistent. The process is easily tailored to multiple clustering based upon the spatial and temporal scales of interest or on generic properties of the individual profile. The sensitivity of the cluster boundaries and group statistics to the addition of new profiles, or to changes in temporal and spatial scale, defines a new environmental characterization.