Sergio DeRada

Modeling of upwelling/relaxation events with the Navy Coastal Ocean Model

Prediction System (COAMPS TM )(COAMPS is a registered trademark of the Naval Research Laboratory). Issues investigated in this study are: NCOM-based model simulations of upwelling and relaxation events, coupling to COAMPS, use of sigma versus hybrid (sigma-z) vertical grids, and coupling with a larger-scale model on the open boundaries. The NCOM simulations were able to reproduce the observed sequence of the upwelling and relaxation events, which can be attributed, in part, to the good agreement between the observed and COAMPS winds. Comparisons with the mooring observations show that COAMPS overestimates shortwave radiation values, which makes the NCOM modeled SSTs too warm in comparison with observations. The NCOM runs forced with different resolution atmospheric forcing (3 versus 9 km) do not show significant differences in the predicted SSTs and mixed-layer depths at the mooring locations. At the same time, during the extended upwelling event, the model runs forced with 3 and 9 km resolution COAMPS fields show differences in the surface circulation patterns, which are the most distinct in the southern portion of the model domain. The model run with 9-km forcing develops a northward flow along the coast, which is not present in the run with 3-km forcing and in observations (for example, HF radar-derived radials). Comparison of the wind patterns of the 3- and 9-km products shows a weakening of the 9-km wind stress along the southern coast of the NCOM model domain, which is responsible for the development of the artificial northward flow in the NCOM run with 9-km forcing.

Development of a Hierarchy of Nested Models to Study the California Current System

The Naval Research Laboratory has developed a hierarch of differing resolution data assimilating models in the Pacific Ocean, which includes global models, regional U.S. West Coast models, and high resolution coastal models such as for the Monterey Bay area. The three regional U.S. West Coast models (from 30 degrees N to 49 degrees N), designed to study the California Current System, are based on the Princeton Ocean Model (POM), the Navy Coastal Ocean Model (MCOM), called NCOM-CCS, and the Hybrid Coordinate Ocean Model (HYCOM), respectively. The NCOM-CCS formulation is a parallel version model capable of running reliably on many computer platforms. The model has nesting capabilities and offers the choice of using the sigma or a hybrid (sigma-z) vertical coordinate. The NCOM-CCS model also includes a coupled ecosystem model based on Chai et al., 2002. A variety of scientific issues related to model initialization, forcing, open boundary conditions, and model sign up are discussed. The focus of this paper is on: the sensitivity of the horizontal resolution of atmospheric forcing on the NCOM-CCs model predictive skills; the impact of open boundary conditions and coupling with global models on reproducing major hydrographic conditions in the California Current System; and the analysis of the model mixed layer predictions and data assimilation issues. Qualitative and quantitative comparisons are made between observations and model predictions for October 2000 - December 2001 period.