The Naval Oceanographic Office (NAVOCEANO) demonstrated new operational capabilities during the large biennial naval exercise called RIMPAC held in July 2008. Participants came from countries that lie along the Rim of the Pacific Ocean and conducted extensive training in the vicinity of the Hawaiian Islands. A 3-km version of the Navy Coastal Ocean Model (NCOM) was spun-up prior to the start of the exercise with forcing provided by a 15-km version of the Navy's Coastal Ocean and Atmospheric Model Prediction System (COAMPS). A water sampling plan was devised to optimize field measurements targeting mesoscale ocean features of interest; namely ″warm″ and ″cold″ core eddies found to the south and north of the island chain. Unique among the observation technologies employed were the shallow water Slocum gliders provided by both Rutgers University and NAVOCEANO, as well as deep sea gliders operated exclusively by NAVOCEANO.

These observations were critical in determining the depth and horizontal extent of each significant eddy. Tidal fluctuations and meteorological conditions were the largest sources of variability impacting the tactical acoustic environment. Persistent trade winds provided the mechanical mixing of the surface layer down to depths of ≈50m. However, in ″wind shadow″ areas behind mountainous islands or during periods of low wind speeds, a strong diurnal ″surface cap″ of very warm water formed that ″disguised″ an eddy's inner core characteristics. NCOM did a fairly good job of capturing this variability once observations began to be assimilated. In contrast, the acoustics application module had a harder time capturing the sharp sub-surface temperature gradient sometimes showing much deeper sonic layer depths than actually existed due to the peculiarity of the embedded sound speed algorithm.

We will discuss NCOM model performance, the impact of the deep sea glider observations and the role of the operational ocean forecaster in providing an appropriate tactical assessment to our warfighter customer.