Modeling the Circulation of the Atchafalaya Basin System During Winter Cold Front Events. Part 1: Model Description and Validation
Mark Cobb, Keen, Timothy R., Walker, Nan D.
The Atchafalaya Bay system consists of a series of five shallow bays in southern Louisiana (U.S.A.) that are dominated by the circulation of the Atchafalaya River plume. Winter cold fronts have a significant impact on the resuspension and transport of sediments in this region, and a better understanding of the circulation during these events is absolutely necessary for detemining the sediment transport patterns of the Atchafalaya Bay system and the adjacent shelf area. Understanding the circulation of this region is also crucial for environmental studies as well. This work describes the implementation of the Navy Coastal Ocean Model (NCOM), a three-dimensional numerical circulation model for tide, river, and wind-forced circulation in the Atchafalaya Bay system. The model has a cell size of ~800 m and is nested to a northern Gulf of Mexico model (cell size ~ 5000 m), which is itself nested to the global NCOM (cell size = 1/8 degree). Atmospheric forcing is supplied by the Navy Operational Global Atmospheric Prediction System (NO-GAPS)(cell size = 1 degree). These models are used to simulate the hydrodynamics of the Atchafalaya Bay system and Atchafalaya river plume between December 1997 and January 1998 during the passage of three winter cold fronts. The water levels, salinity, and currents predicted by NCOM are in reasonable argeement with available measurements and tide-gauge elevation data. Errors in ebb tides and wind-driven circulation are attributable to uncertainties in the bathymetry and the low spatial and temporal resolution of the NOGAPS wind fields.