Applying Basin-Scale Hindcast in Providing Open Boundary Conditions for Nested High-resolution ROMS Coastal Circulation Modeling

Ruoying He
Woods Hole Oceanographic Institution

The offshore ocean can exert a significant influence in many coastal regions due to a wide range of processes such as basin-scale seasonal and inter-annual variability, boundary current meanders, and meso-scale and submeso-scale eddies. To effectively represent the impact of this offshore variability on a coastal ocean setting, the coastal model must be driven by open boundary conditions (OBCs) that can represent the state of the open ocean and its variability. The Hybrid Coordinate Ocean Model (HYCOM) Global Ocean Data Assimilation Experiment (GODAE) hindcast was used for this purpose by using it to provide boundary conditions to a nested Regional Ocean Modeling System (ROMS).

The nested (1st-level nesting) ROMS provided circulation hindcast for the coastal area encompassing the Gulf of Maine (GOM) and the Middle Atlantic Bight (MAB). Inside this regional ROMS, additional two smaller-scale ROMS models were embedded (2nd-level nesting) to provide high-resolution model realizations of circulation in the Gulf of Maine and the Mid-Atlantic Bight shelf-break region, respectively. Our objective is through such multi-nesting approach, to bring deep-ocean influence to the coastal region in a dynamically consistent, and quantitatively accurate manner, thereby facilitating the realism and fidelity of high-resolution coastal circulation modeling. We report here some preliminary results of such effort.