One of the challenges in the simulation of coastal ocean dynamics is the vast range of length and time scales present. While global- and basin-scale processes and currents can be captured quite well with computationally-inexpensive hydrostatic models, smaller-scale features such as shoaling nonlinear internal waves and bores, coastal fronts, and other convective processes require the use of a nonhydrostatic model to capture dynamics accurately. In this talk we introduce the nonhydrostatic capabilities of the General Curvilinear Coastal Ocean Model (GCCOM) in a stratified environment. GCCOM is a three-dimensional, nonhydrostatic Large Eddy Simulation (LES) model that can run in a fully three-dimensional general curvilinear coordinate system. While this model was validated for unstratified flows, we present on recent advances of the model to simulate stratified flows. A suite of test cases widely used as benchmarks for assessing the nonhydrostatic capabilities for gravity-driven flows. These validation experiments demonstrate that GCCOM can resolve complex nonhydrostatic phenomena in stratified flows with numerical accuracy and mass and energy conservation.
In the second part of the talk, I present the integration of a data assimilation framework for GCCOM with the aim to study sub-mesoscale processes. When provided with the proper data, mesoscale phenomena have been modeled with a certain level of accuracy; however, many sub-mesoscale features are still poorly modeled, causing them to remain largely unpredictable. 3D nonhydrostatic models are required to accurately capture these key dynamics. Although this implementation is essential for the successful development of physical ocean models, a major challenge posed by this approach is the high computational cost incurred by high-resolution numerical models with three-dimensional data assimilation schemes. However, by interfacing GCCOM with NCAR's Data Assimilation Research Testbed (DART), we enable GCCOM to integrate observations into its system. This research included Observation System Simulation Experiments (OSSEs) for test cases using very steep seamounts. Results demonstrated that the DARTG-CCOM model can assimilate high-resolution observations using as few as 30 ensemble members.