Spectral model simulation of wind-driven subinertial circulation on the inner Texas-Louisiana shelf

A spectral shelf circulation model based on a coastal trapped wave mode approximation is developed and employed to simulate time-dependent, wind induced circulation on the inner Texas-Louisiana continental shelf. This is the first successful development and application of a coastal trapped wave or shelf mode model to wind driven circulation on the Texas-Louisiana inner shelf domain. The model is formulated within a boundary fitted, curvilinear coordinate system. Wind forcing includes both cross-shelf and along-shelf components. In contrast to previous shelf mode modeling studies, quadratic bottom stress parameterization is adopted.; The Texas-Louisiana Shelf Circulation and Transport Processes Study (LATEX-A) of the Louisiana-Texas Shelf Physical Oceanography Program (LATEX) and collateral sources collected data that were analyzed and used for dynamic upstream boundary conditions, wind forcing, computation of coastal trapped wave modes, and model verification. These data include approximately 32 month hourly records of current speed and direction data from 76 current meters at 30 locations and of wind and pressure data from 15 meteorological moorings, as well as data from 1139 hydrographic stations, five year records of hourly coastal water level at 10 tide gauges, and high resolution bathymetry.; The focus of this study is primarily on the weatherband frequencies (periods from two to ten days), and encompasses continental shelf waves. The long period (annual) signal is addressed as well. Observations of subinertial along-shelf currents and water level were compared with simulations of specific episodes ranging from one to 32 months in length. Model performance at near inertial frequencies was surpassed by that observed for weatherband to seasonal and lower frequencies. Seasonal reversals in mean along-shelf current direction are a predictable response to wind forcing, but baroclinic processes also greatly influence seasonal response.; Free continental shelf waves have been identified for the first time from subinertial current meter and water level data on the inner Texas-Louisiana shelf. Waves excited near Atchafalaya Bay, Louisiana by Hurricane Andrew are observed to propagate as far south as the Rio Grande, a distance exceeding 800 kilometers.