Use Of SAR and ASAR Images to Derive Eddy Diffusivity Maps of the Ocean Surface From Multifractal and Topological Statistical Methods

J.M. Redondo⁽¹⁾, M. Diez⁽²⁾, A. Matulka⁽¹⁾, E. Sekula⁽¹⁾, R. Castilla⁽³⁾ and A.M. Tarquis⁽⁴⁾

⁽¹⁾ Univ. Politecnica de Catalunya, Dept. Fisica Aplicada, Barcelona, Spain
⁽²⁾ Ports de la Generalitat, , 08800, Vilanova i la Geltru, Barcelona, Spain
⁽³⁾ Univ. Politecnica de Catalunya, Dept. Mecanica de Fluids, Terrasa, Spain
⁽⁴⁾ Univ. Politecnica de Madrid, CEIGRAM, Ciudad Universitaria, Madrid, Spain

Abstract

The satellite-borne SAR and ASAR seems to be an excellent system not only to detect man-made oil spills and tensioactive slicks but it also detects dynamic features and the ocean eddies of different sizes. The study of the topology of the regions of different rugosity of the ocean can map the vortical, eliptical regions as well as the hyperbolic shear dominated areas, is also a convenient tool to investigate the eddy structures, the scale to scale energy and enstrophy transfer of a certain area, and to calculate the eddy diffusivity values. The effect of bathymetry and local currents are important in describing the ocean surface behavior. In the NW Mediterranean the maximum eddy size agrees remarkably well with the limit imposed by the local Rossby deformation radius using the usual thermocline induced stratification, Redondo and Platonov (2001). The Rossby deformation radius, is attained when buoyancy and Coriolis forces are in equilibrium, and it is defined as Rd = (N/f)h, where N is the Brunt-Vaisalla frequency, f is the local Coriolis parameter (f=2Osin a), where O is the rotation of the earth and a is the latitude) and h is the thermocline depth, Rd is about 6-20 Km.

A geometry of gray scale ranges and boundaries of spatial dynamic surface features may contain new helpful information. Already we used multi-fractal analysis techniques to investigate man-made oil spills, Redondo and Platonov(2009), Platonov et al.(2008). We now work in the aplication of these techniques to the analysis of ocean surface multi-fractal features (eddies, mushroom-like currents, etc.) to understand the scale to scale transport. (Redondo et al. 2008)(Diez et al. 2008).

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Platonov A. Carrillo A. Matulka A, Sekula E., Grau J. Redondo J.M. and Tarquis A. (2008)Multifractal observations of eddies, oil spills and natural slicks in the ocean surface. Il Nuovo Cimento C 31,5-6, 861-880.

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Diez M., Bezerra M.O., Mosso C., Castilla R. and Redondo J.M. (2008) Experimental measurements and diffusion in harbor and coastal areas. Il Nuovo Cimento C 31, 5-6, 843-859.

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