Real-time ocean data assimilation and prediction with global NCOM

The Naval Research Laboratory (NRL) at Stennis Space Center has developed a global implementation of the Navy Coastal Ocean Model (NCOM). Global NCOM encompasses the open ocean to 5 m depth in a curvilinear global model grid with 1/8 degree grid spacing at 45°N, extending from 80°S to a complete Arctic cap with grid singularities mapped into Canada and Russia. The model employs 40 vertical sigma-z levels, with sigma in the upper ocean and coastal regions, and z in the deeper ocean. The real-time system uses Navy Operational Global Atmospheric Prediction System (NOGAPS) 3-hourly wind stresses and heat fluxes. Operationally available sea surface temperature (SST) and altimetry (SSH) data are incorporated into NAVOCEANO Modular Ocean Data Assimilation System (MODAS) and Navy Layered Ocean Model (NLOM) analyses and forecasts of SSH and SST. These in turn are combined with the MODAS synthetic database to yield three-dimensional fields of temperature and salinity for assimilation into global NCOM. We describe the analysis and forecast system, present selected evaluations of the model performance, and discuss planned upgrades to the model and data assimilation methods.