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Non-Gaussian velocity probability density functions in the Mediterranean sea
J. Isern-Fontanet, E. García-Ladona, J. Font, A. García-Olivares
Institut de Ciències del Mar (CSIC)
jisern@icm.csic.es(Abstract received 04/27/2005 for session A)
ABSTRACT
Velocity Probability Density Functions (PDF) are a key information to study complex flows and of great importance to model particle dispersion. PDF computed in the Mediterranean sea from both, surface Lagrangian data and geostrophic velocities derived from Sea Level Anomalies exhibit non-Gaussian shapes, in agreement with the observations done in other ocean regions. Relatively recent studies on 2D turbulence have shown that non-Gaussian PDF may be associated to the presence of coherent vortices. To investigate this, a flow partition criterion based on the Okubo-Weiss parameter (W) has been used to separate the contribution of coherent vortices and the background field. Then, the velocity PDF have been recomputed showing that only a 20\% of the vortices identified in the data set are the main responsible of this non-Gaussianity. This vortices, defined as intense vortices in previous works, are those vortices with amplitudes of about $a\geq 2\sigma_W$ and radius of the order of 40 km.
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2005 LAPCOD Meeting, Lerici, Italy, June 13-17, 2005