Lagrangian statistics in unforced barotropic flows
J. Lacasce1999, Journal of Marine Research
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Abstract
We consider the dispersion of particles in potential vorticity (PV)-conserving ows. Because particle drift is preferentially along the mean PV contours, Lagrangian dispersion is strongly anisotropic. If the mean PV eld moreover is spatially variable, as when there is topography, the anisotropy is more clearly visible in the dispersion of displacements along and across the mean PV eld itself. We examine several numerical examples of unforced barotropic ows; in all cases, this ''projected'' dispersion is more anisotropicthan that in cartesian (x, y) coordinates.What differs is the rate at which spreading occurs, both along and across contours. The method is applicable to real data, as is illustrated with oat data from the deep North Atlantic. The results suggest a preferential spreading along contours of (barotropic) f/H.
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We consider the dispersion of particles in potential vorticity (PV)-conserving ows. Because particle drift is preferentially along the mean PV contours, Lagrangian dispersion is strongly anisotropic. If the mean PV eld moreover is spatially variable, as when there is topography, the anisotropy is more clearly visible in the dispersion of displacements along and across the mean PV eld itself. We examine several numerical examples of unforced barotropic ows; in all cases, this ‘‘projected’’ dispersionis more anisotropicthan that in cartesian (x, y) coordinates.What differs is the rate at which spreadingoccurs, both along and across contours.The method is applicable to real data, as is illustrated with oat data from the deep North Atlantic. The results suggest a preferential spreading along contours of (barotropic) f/H.
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