Blending Model Results With Observations in the SBC/SMB Study

The 1993-1999 Santa Barbara ­V Santa Maria Basin (SBC/SMB) circulation study, conducted by the Center for Coastal Study of the Scripps Institution of Oceanography, represents a major research effort towards designing a coastal ocean observing system (COOS). During the 6-year period, at any time there were always about a dozen current meter and temperature moorings maintained in the study area. The moored measurements have continuous spatial and temporal coverage and are most trustworthy (compared to, say, shipboard observation and remote sensing), and thus are ideally suited as the ­\x9Dabsolute­Ý reference in describing ocean states. On the other hand, the mooring observations are point measurements, and it is unlikely that the moored data alone will ever have adequate spatial resolution in a COOS. There is need for complementary data. Coastal circulation models could play a crucial role in filling this gap. Examples of using coastal ocean models in the SBC/SMB study to obtain ocean state estimation will be presented. A coastal ocean model typically is driven by the atmospheric forcing (which must be specified over the entire model domain) and the mass and momentum exchange across ­\x9Dopen­Ý boundaries. In this study the atmospheric forcing is derived from a dozen met buoy observations plus numerous coastal weather stations collected during the SBC/SMB study. The need to specify open-ocean water mass exchange is circumvented by assimilating the moored temperature data. The possibility of impinging open-ocean eddy, however, is ruled out. Two research issues are addressed. First, an attempt is made to blend the model results with moored velocity observations. Second, the impact of data assimilation on model results is examined. These two issues, one dealing with the initialization in ocean forecasts and nowcasts and the other with the sampling design, are fundamental to any COOS. The comprehensive SBC/SMB study affords an excellent opportunity for a COOS feasibility study.