Objective Maps of Near-Surface Flow States near Point Conception, California

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Abstract
Objective streamfunction and velocity potential maps of three commonly observed flow states near Point Conception, California, are derived from moored current-meter and drifter observations. The states are defined using current-meter data. Drifter data are sorted by flow state and averaged within spatial bins to resolve their spatial structures. Spatial correlations of drifter data show the along-shelf and cross-shelf decorrelation distances are approximately 45 and 25 km, respectively. This information is used to make the objective streamfunction and velocity potential maps. The total velocity is represented as the sum of the rotational, nondivergent streamfunction component and the irrotational, divergent velocity potential component. The velocity derived from the streamfunction is much stronger than that derived from the velocity potential. The streamfunction is sufficiently well resolved to make meaningful vorticity maps. The velocity potential indicates a source term in the western Santa Barbara Channel consistent with wind stress curl-driven upwelling, but divergence maps derived from the velocity potential are very noisy, making comparisons with wind stress curl mapped on the same scales problematic.