T. L. Townsend, E. P. Chassignet, H. E. Hurlburt, W. J. Schmitz Jr., and A. J. Wallcraft, NRL and RSMAS
At 7 km horizontal grid resolution, basin-scale models of the Atlantic Ocean are able to achieve realistic separation of the Gulf Stream at Cape Hatteras, NC, but such models continue to have difficulty downstream simulating the mean path, strength, and variability of this major ocean current. A collaborative effort is underway to improve these characteristics in the dynamical model component of the present near real-time 7 km data-assimilative Atlantic HYCOM system. Numerous simulations have been performed to assess the impact of open boundary relaxation time scales, choice of advection scheme, choice of vertical coordinate reference, passage sills in the model bottom topography, viscosity parameterization, choice of turbulence closure scheme, sensitivity to strength of wind forcing, and horizontal grid resolution; the last undertaken by comparison to a 3.5 km simulation. Improvement in simulation of the Gulf Stream System is determined via model-data and model-model inter-comparisons with emphasis on mean and variability and also involves investigation of model representation of influencing factors. The most recent results of this on-going effort will be presented.