Examples of oil spills and slicks in a SAR image near Barcelona. 

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... oil pollution of Gulf of Lion in the NW Mediterranean has been studied with SAR images during the period 1999 -2005. We have analyzed these SAR images with respect to other surface features such as wind, river plumes, eddies and convergence areas. Some results of our statistical analysis are presented showing that the NW Mediterranean is most polluted along the main ship traffic routes, but comparatively less that near other routes in the Indic and the Pacific. The oils spill index is higher than one. The sizes of the detected oil spills vary over a large range, and if the statistics of the largest accidents are also considered on a longer timescale, we show that Zipf's Law, relating the frequency and the size of the spill in a hyperbolic fashion is applicable. Advanced image analysis techniques, such as the calculation of the multi-fractal dimensions of the observed SAR signatures, have been applied to distinguish between natural slicks and antropogenic spills. Fractal dimensions can also be used to predict the time of release of the spill, non-dimensionalised with local turbulent dissipation. The multi-scale appearance and the topological structure of the slicks and spills may also be used as a useful measure of the diffusivity, yielding additional information which in turn may improve automated detection algorithms and be used in numerical models. The advances in satellite detection techniques in recent years have been able to highlight marine pollution and other previously ignored sea surface features such as vortices, fronts, convection areas, etc. There is also more public awareness to both the large nautical catastrophes (e.g. oil tankers Amoco Cadiz, Exxon Valdez and recently Erika and Prestige) and the habitual smaller oil spills from the ships. The range of marine pollution events should even consider, due to their overall importance, the very much smaller oil spills of a few square meters caused by small boats. The middle size oil spills often originate due to coastal sources and from small accidents or habitual cleaning of ballast water in ships. The larger oil spills are caused by crude/oil tankers catastrophic accidents of varied consequences but no systematic study except the CLEAN-SEAS project of the European Union [1,2] has been able to compare a wide range of detected oil spills. To obtain an updated vision of the dynamical processes and of the superficial pollution of the Northwest Mediterranean Sea we used results from SAR and ASAR and design strategies for oil spill detection and discrimination. Extending and comparing statistically knowledge obtained during 1996-1998 with recent years (image data set, oil spills statistic temporal/spatial analysis, thematic maps) does not show significant changes. Improvements in software based in multi-fractal analysis applications allow to distinguish between the different detected sea surface phenomena, in particular it is important to be able to discriminate between natural slicks and oil spills as shown in figure 1. The aim of this work is to apply our experience obtained during Clean Seas EU Project (1996-2000) and others, to extend and compare statistically our baseline knowledge of the state of the pollution in the North-western Mediterranean The SAR images analysed, obtained during 1996-1998 were generally from the Clean Seas European project (near 900 images with 300 in the North-western Mediterranean Sea area). New images are obtained from ESA archives (ENVISAT and ERS-2 images during 1998-2003) as well as further SAR/ASAR images obtained directly from ESA contract (C1P.2240) (2000- 2006). It is important to obtain a more updated vision of the associated sea surface dynamical processes in terms of the turbulent parameters needed to predict spill behaviour. Also for other marine surface phenomena, such as vortices, fronts, convergence areas, etc, deteced by SAR-ASAR the improvement in their statistic and the comparative analysis with in situ observations provides important data assimilation tools in order to improve numerical models of turbulent diffusion in the ocean surface at different scales. In particular the role of the Rossby deformation radius on mesoscale turbulent diffusion will be discussed following references [3-6] considering the application of multifractal analysis to distinguish between antropogenic oil spills and natural slicks Oceanic flow may be considered as turbulent motions under the constraints of geometry, stratification and rotation. At large scales these flows tend to occur mostly along isopycnal surfaces due to the combined effects of the very low aspect ratio of the flows (the motion is confined to thin layers of fluid) and the existence of stable density stratification. The effect of the Earth's rotation is to reduce the vertical shear in these almost planar flows. The combined effects of these constraints are to produce approximately a two-dimensional turbulent flow, there the nergy input at a given scale is transferred to larger scales, because these constraints stop vortex lines being stretched or twisted. Physically this upscale energy transfer occurs by merging of vortices and leads to the production of coherent structures in the flow that contain a significant part of the energy. This scenario is an appropriate model for geophysical flows which are known to contain very energetic meso-scale oceanic eddies. This upscale transfer of energy is inhibited at the Rossby deformation radius ...