Editorial Type:
Article
Article Type:
Research Article

Non-Gaussian Velocity Probability Density Functions: An Altimetric Perspective of the Mediterranean Sea

Jordi Isern-Fontanet Institut de Ciències del Mar (CSIC), Barcelona, Spain

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Emilio García-Ladona Institut de Ciències del Mar (CSIC), Barcelona, Spain

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Jordi Font Institut de Ciències del Mar (CSIC), Barcelona, Spain

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Antonio García-Olivares Institut de Ciències del Mar (CSIC), Barcelona, Spain

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Print Publication:
01 Nov 2006
DOI:
https://doi.org/10.1175/JPO2971.1
Page(s):
2153–2164
Restricted access

Abstract

Velocity probability density functions (PDFs) are a key tool to study complex flows and are of great importance to model particle dispersion. The PDFs of geostrophic velocities derived from sea level anomalies maps for the Mediterranean Sea have been computed and analyzed, guided by recent results found in studies of two-dimensional and geostrophic turbulence. At the basin scale results show that the geostrophic velocity PDF derived from SLA maps is non-Gaussian. To understand the origin of this non-Gaussianity, a topological partition of the flow based on the Okubo–Weiss parameter is applied to separate the contribution of coherent vortices from the background field. After such separation the non-Gaussian part of the PDF appears mostly associated with the presence of such structures. Only about 20% of the vortices identified in the dataset are mainly responsible for this deviation. These vortices, called intense vortices in previous works, are those vortices with values of the amplitude larger than or equal to two standard deviations of the Okubo–Weiss parameter and correspond to vortices with a radius on the order of 40 km.

Corresponding author address: Jordi Isern-Fontanet, Département d’Océanographic Physique et Spatiale, IFREMER, Centre de Brest Technopôle de Brest-Iroise, BP 70, F-29280 Plouzané, France. Email: jisern@ifremer.fr

Abstract

Velocity probability density functions (PDFs) are a key tool to study complex flows and are of great importance to model particle dispersion. The PDFs of geostrophic velocities derived from sea level anomalies maps for the Mediterranean Sea have been computed and analyzed, guided by recent results found in studies of two-dimensional and geostrophic turbulence. At the basin scale results show that the geostrophic velocity PDF derived from SLA maps is non-Gaussian. To understand the origin of this non-Gaussianity, a topological partition of the flow based on the Okubo–Weiss parameter is applied to separate the contribution of coherent vortices from the background field. After such separation the non-Gaussian part of the PDF appears mostly associated with the presence of such structures. Only about 20% of the vortices identified in the dataset are mainly responsible for this deviation. These vortices, called intense vortices in previous works, are those vortices with values of the amplitude larger than or equal to two standard deviations of the Okubo–Weiss parameter and correspond to vortices with a radius on the order of 40 km.

Corresponding author address: Jordi Isern-Fontanet, Département d’Océanographic Physique et Spatiale, IFREMER, Centre de Brest Technopôle de Brest-Iroise, BP 70, F-29280 Plouzané, France. Email: jisern@ifremer.fr

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