Coastal model simulation of the Santa Barbara Channel circulation

The Santa Barbara Channel (SBC) is located at the interface of cold Central California Coast (CCC) water and warm Southern California Bight (SCB) water. The temperature difference along the channel is weak in winter and strong in summer. Winds off the CCC are equatorward and are upwelling-favorable in spring and summer. This equatorward wind is sheltered by Santa Ynez mountains, making the SCB and the eastern SBC a region of low wind stress and high wind curl. Observations indicated that currents in the SBC are a superposition of a large-scale poleward through flow and an interior cyclonic circulation, and that the along-channel pressure gradient and local wind are important forcing. In this study, a 3-D primitive equation coastal general circulation model is used to examine the response of the SBC circulation to these forcing.; The density forcing is first examined. The data base are from 8 current meter moorings distributed along the 100 m isobath inside the channel as part of the SBC-SMB study. Model simulation is for the first 8 months of 1994 when the data coverage is most complete. Seasonal, large-scale changes of water mass are accounted for by assimilating of temperature and salinity data. The assimilation is based on a local correction method weighted by the model-data misfits, and is applied only to model predictions in the channel. For the outer domain, the model temperatures are replaced with values interpolated from the observations.; The model generates a cyclonic eddy centered at the western portion of the SBC. The model's monthly mean currents and horizontal shears agree well with the observations.; The model is also applied to study the wind forcing. To isolate the wind response, the model does not use data assimilation. The SBC-SMB study supplies a comprehensive buoy observation of detailed temporal and spatial surface wind structures. The model is driven by the observed time-varying, spatially non-uniform winds for the same 8 month period.; Empirical orthogonal function analysis of the model results suggests that the local wind stress is important in the open ocean and over the southern part of the western entrance, whereas the along-channel pressure gradient is important along the coast. (Abstract shortened by UMI.)...