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Abstract :
[en] A West Florida Shelf (WFS) model is constructed by nesting the Regional Ocean Model System (ROMS) in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) to include both local and deep-ocean forcing, particularly the Gulf of Mexico Loop Current (LC). Hindcast experiments from 2004 to 2006 are presented and compared to observed temperature (moorings and BSOP profiling floats), ADCP velocity time series and HF-Radar surface currents. Two different mixing schemes (Mellor Yamada level 2.5 and K-Profile Parameterization, KPP) are tested and the importance of the vertical resolution for mixing is addressed. The model results of those different configurations are compared to temperature observations on the shelf. Results obtained with the Mellor Yamada scheme are closer to observations during winter (negative buoyancy flux and strong winds) while in summer (positive buoyancy flux and in general weaker wind) the KPP scheme produces more realistic results. Given the present HYCOM configuration we assessed the benefit of nesting ROMS in HYCOM compared to nesting ROMS in climatology. The model solutions on the shelf were compared to various in situ data. The model performed best when using the HYCOM boundary values. Simulated trajectories for drifters deployed off Tampa Bay and Sarasota were used to address the evolution of Karenia brevis concentrations during the 2005 red tide. Near surface drifters were advected offshore, whereas drifters deployed in the bottom Ekman layer matched the subsequently observed Karenia brevis distributions, showing the importance of the 3D structure of coastal ocean currents for red tide on the WFS. As a first attempt at assimilating CODAR surface currents we used an ensemble simulation carried out under different wind forcings to estimate the error covariance of the model state vector and the covariance between the ocean currents and the wind. Improvements were obtained for the modeled currents, not only at the surface, but also at depth.
