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Since January 2009, two long-range high-frequency (HF) radar systems have been collecting hourly high-spatial-resolution surface current data in the southeastern corner of the Bay of Biscay. The temporal resolution of the HF radar surface currents permits simulating drifter trajectories with the same time step as that of real drifters deployed in the region in 2009. The main goal of this work is to compare real drifter trajectories with trajectories computed from HF radar currents obtained using different methods, including forecast currents. Open-boundary modal analysis (OMA) is applied to the radar radial velocities and then a linear autoregressive model on the empirical orthogonal function (EOF) decomposition of an historical data series is used to forecast OMA currents. Additionally, the accuracy of the forecast method in terms of the spatial and temporal distribution of the Lagrangian distances between observations and forecasts is investigated for a 4-yr period (2009–12). The skills of the different HF radar products are evaluated within a 48-h window. The mean distances between real trajectories and their radar-derived counterparts range from 4 to 5 km for real-time and forecast currents after 12 hours of simulations. The forecast model improves persistence (i.e., the simulations obtained by using the last available OMA fields as a constant variable) after 6 hours of simulation and improves the estimation of trajectories up to 28% after 48 hours. The performance of the forecast is observed to be variable in space and time, related to the different ocean processes governing the local ocean circulation.

The development of a coastal ocean circulation model involves many challenges, including the interaction of complex coastline and topography and the prediction of mesoscale oceanographic features. The Innovative Coastal-Ocean Observing Network (ICON) developed a Monterey Bay ocean circulation model to resolve these challenges. This study examines two different ICON model cases. The first ICON model case was forced with the 100 km NOGAPS winds while the other was forced with the 9 km COAMPS winds. The comparison demonstrated that the 9 km COAMPS-forced case produced better resolution of the ocean mesoscale. This was shown through examination of the daily sea surface temperature fields and the daily surface ocean currents. Time series of sea surface temperature showed a strong seasonal cycle. After removal of the seasonal cycle, the existence of mesoscale features was even more dramatic. A case study at Pt. Sur showed the evolution of mesoscale features associated with an upwelling event., http://archive.org/details/impactofhighreso109451839, US Navy (USN) author

Observations from disparate observational assets, including tide gauges, moorings, and high-frequency (HF) radars, were used to depict the tidal variability, and to evaluate model tidal simulations, for a region off central California, including the Monterey Bay. For this study, the hydrodynamic model was forced only with tides derived from a large-scale model for the northeast Pacific Ocean. Homogeneous density, and initially horizontally uniform density stratification, cases were considered. The model successfully reproduced tidal sea-surface height variations within the model domain, a determined by comparisons with sea level or bottom pressure measured at six locations. To achieve tidal currents with realistic amplitudes, as determined from HF radar and moored measurements, it was found that barotropic velocity, as well as sea level, from the large-scale regional tidal model must be included in specifying the open-boundary condition. However, even with such forcing, the model with homogeneous density field under-predicted the semidiurnal and diurnal barotropic currents as estimated from depth-averaged currents measured at 11 locations. In the diurnal frequency band, the observed surface and nearshore depth-averaged currents are likely influenced by meteorological forcing, which was not included in the model., Pub. in Deep-Sea Research II, v56 p199-218, 2009.

The development and implementation of a real-time ocean forecast system based on the Regional Ocean Modeling System (ROMS) off the coast of central California are described. The ROMS configuration consists of three nested modeling domains with increasing spatial resolutions: the US West coastal ocean at 15-km resolution, the central California coastal ocean at 5 km, and the Monterey Bay region at 1.5 km. All three nested models have 32 vertical sigma (or terrain-following) layers and were integrated in conj. unction with a three-dimensional variational data assimilation algorithm (3DVAR) to produce snapshots of the ocean state every 6 h (the reanalysis) and 48-h forecasts once a day. This ROMS forecast system was operated in real time during the field experiment known as the Autonomous Ocean Sampling Network (AOSN-II) in August 2003. After the field experiment, a number of improvements were made to the ROMS forecast system: more data were added in the reanalysis with more careful quality control procedures, improvements were made in the data assimilation scheme, as well as model surface and side boundary conditions. The results from the ROMS reanalysis are presented here. The ROMS reanalysis is first compared with the assimilated data as a consistency check. An evaluation of the ROMS reanalysis against the independent measurements that are not assimilated into the model is then presented. This evaluation shows the mean differences in temperature and salinity between reanalysis and observations to be less than 1 degrees C and 0.2 psu (practical salinity unit), respectively, with root-mean-square (RMS) differences of less than 1.5 degrees C and 0.25 psu. Qualitative agreement is found between independent current measurements and the ROMS reanalysis. The agreement is particularly good for the vertically integrated current along the offshore glider tracks: the ROMS reanalysis can realistically reproduce the poleward California Undercurrent. Reasonably good agreement is

The Navy Coastal Ocean Model (NCOM) is a free-surface, primitive-equation model that is under development at the Naval Research Laboratory (NRL). The NCOM-based model of the Monterey Bay area is evaluated during a series of upwelling and relaxation wind events in August-September of 2000. The model receives open boundary conditions from a regional NCOM implementation of the California Current System and surface fluxes from the Navy Coupled Ocean/ Atmosphere Mesoscale Prediction System (COAMPS(TradeMark))(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 9km resolution COAMPS fields show differences in the surface circulation., Published in Journal of Geophysical Research, v112, C06023, 2007. The original document contains color images.

The ICON model, a high-resolution, dataassimilating, model of the Monterey Bay area, was initially designed for studying mesoscale features such as eddies and upwelling filaments. Tidal forcing is now being implemented into this model to facilitate short-term particle-tracking studies, and to move towards a real-time operational forecast model.

The development of a coastal ocean circulation model involves many challenges, including the interaction of complex coastline and topography and the prediction of mesoscale oceanographic features. The Innovative Coastal-Ocean Observing Network (ICON) developed a Monterey Bay ocean circulation model to resolve these challenges. This study examines two different ICON model cases. The first ICON model case was forced with the 100 km NOGAPS winds while the other was forced with the 9 km COAMPS winds. The comparison demonstrated that the 9 km COAMPS-forced case produced better resolution of the ocean mesoscale. This was shown through examination of the daily sea surface temperature fields and the daily surface ocean currents. Time series of sea surface temperature showed a strong seasonal cycle. After removal of the seasonal cycle, the existence of mesoscale features was even more dramatic. A case study at Pt. Sur showed the evolution of mesoscale features associated with an upwelling event.