Three Dimensional Vorticity Field in the California Current System
2006
Montenegro, Gonzalo
Hydrographic data has traditionally been used only to determine dynamical features, specifically dynamic topography and geostrophic currents relative to an assumed level of no motion. However, the assumption of geostrophic balance has been questioned because of the neglect of ageostrophic effects. Measuring vorticity and vertical motion has always been technically demanding and costly. Due to the importance of these parameters new techniques have been developed, among them a diagnostic technique known as the C-vector Method, which uses the wind stress and the geostrophic balance as forcing functions to infer these quantities. Using this technique, the three dimensional vorticity field was computed for the California current system during the Coastal Transition Zone (CTZ) program. Hydrographic (CTD) and wind data sets were used assuming a quasi-geostrophic system. Also computed was vertical vorticity of the C-vector, known as the Psi function, which has a direct relationship with the vertical velocity, making it possible to infer upward or downward motion in coastal waters. A satisfying correlation was found between surface temperature fields, satellite imagery, and vertical motions inferred from the Psi function. The C-vector has therefore been shown to be a very reliable method of diagnosing vorticity and vertical circulation
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