Development and Evaluation of the Navy's Global Coupled Atmosphere-Ocean-Sea Ice Prediction System

The Naval Research Laboratory is developing a global coupled atmosphere-ocean-sea ice seamless prediction system with the goals of improving of short-term and long-term predictions, as well as an enhanced understanding of environmental interactions. The system utilizes the Navy's Global Environmental Model (NAVGEM), the Navy's HYbrid Coordinate Ocean Model (HYCOM), and the Los Alamos National Laboratory's sea ice (CICE) model for the atmosphere, ocean, and sea ice model respectively. To couple the models, the National Unified Operational Prediction Capability (NUOPC) tools built on top of Earth System Modeling Framework (ESMF) are used. This coupling framework allows for the communication between the modeling components without significant changes in the NAVGEM, HYCOM, and CICE code.

An introduction and case studies using this model are presented. The coupled model can be run by selecting desired modeling components. If the atmosphere or ocean is not desired, data representations of these components are used. There is no data sea ice component, and the simple NAVGEM thermodynamic sea ice model is used if the sea ice model is not desired. Preliminary testing of case studies determined that the coupled model aids in some processes, while other model deficiencies are enhanced. For example, stand-alone NAVGEM hindcast simulations did not capture an April 2011 Madden-Julian Oscillation (MJO) event observed by the Tropical Rainfall Measuring Mission (TRMM) observations. When the coupled system is used, the onset of the MJO event is reasonably well simulated when compared to TRMM suggesting the interactions between the ocean and atmosphere are important when forecasting this MJO event. An example of a model deficiency that is enhanced during the coupling is that a global ocean cold bias occurs. Last, future directions for Navy's coupled model will be discussed.