Impact of Mean SSH on Synthetic Profiles and Data Assimilation: Currents and Transport in Global NCOM

Four year-long parallel experiments were performed on variations of the Naval Research Laboratory's (NRL) global ocean modeling system. This system has three main components: the global NRL Layered Ocean Model (NLOM), the global Navy Coastal Ocean Model (NCOM), and the Modular Ocean Data Assimilation System (MODAS). By targeting the strengths of each of these elements, the combined system has improved coverage, resolution and skill to provide global analyses, forecasts and boundary conditions. Our experiments examine changes in the derivation of synthetic temperature and salinity profiles for data assimilation. We evaluate the global impact of these variations on model simulations by comparison with unassimilated vertical temperature profiles and WOCE drifter trajectories. We demonstrate that improved resolution of sea surface height (SSH) and better treatment of the differences between MODAS and NLOM mean SSH leads to more accurate NCOM model results.