The Ocean Modeling System (ROMS): Nested 4D-Var and Hybrid Nesting and Coupling

This proposal builds upon previous, ONR-funded development of the ROMS framework to improve the ocean modeling and prediction capabilities of the U.S. Navy. We have developed state-of-the-art variational ocean data assimilation and ensemble prediction systems based on conventional practices in operational numerical weather prediction. Also, we have developed algorithms to quantify the impact of the observations in an analysis/forecast system and the uncertainty in the resulting circulation estimates. I propose to focus my research on the following tasks: (i) develop hybrid nesting capabilities, (ii) 4D-Var across nested grids, (iii) expand model coupling, and (iv) documentation, training, and workshops. We propose, in collaboration with Prof. A. Moore (separate proposal) to combine the nested capabilities of ROMS with the 4D-Var system allowing users to assimilate data seamlessly across nested model grids. It facilitates incorporating observations from new rapid-sampling platforms, such as gliders and AUVs, and high-resolution remote sensing platforms such as SWOT and SAR imagery. It will maximize the information return from such observations when combined with data assimilation into very high-resolution nested grids capable of resolving the sub-mesoscale circulation. The ROMS nesting algorithms are unique and robust allowing various downscaling capabilities in coastal regions with complex topography and dynamics. As a next step, I propose to expand these algorithms to enable hybrid nesting for the synchronous exchange of information between any basin-scale model and a hierarchy of nested ROMS coastal models. Also, I propose to expand the current ROMS multi-model coupling capabilities to include additional Earth System Model (ESM) components. The ROMS coupling algorithms use the Earth System Model Framework (ESMF) library with the National Unified Operation Prediction Capability (NUOPC) Layer to facilitate compliance between coupling component interactions. Lastly, I also propose to continue the webbased documentation and to organize annual workshops and tutorials.