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10 pages, 9 figures, 1 table.-- PACS: 47.20.Bp; 47.20.Ky; 47.10.-g; 47.35.-i ; We study, from the numerical point of view, instabilities developed in a fluid layer with a free surface in a cylindrical container which is nonhomogeneously heated from below. In particular, we consider the case in which the applied heat is localized around the origin. An axisymmetric basic state appears as soon as a nonzero horizontal temperature gradient is imposed. The basic state may bifurcate to different solutions depending on vertical and lateral temperature gradients and on the shape of the heating function. We find different kinds of instabilities: extended patterns growing on the whole domain, which include those known as targets, and spiral waves. Spirals are present even for infinite Prandtl number. Localized structures both at the origin and at the outer part of the cylinder may appear either as Hopf or stationary bifurcations. An overview of the developed instabilities as functions of the dimensionless parameters is presented in this article. ; This work was partially supported by the Research Grant MCYT (Spanish Government) Nos. BFM2003-02832, MTM2004-00797, MTM2006-14843-C02-01, CCYT (JC de Castilla-La Mancha) Nos. PAC-05-005-01/02, SIMUMAT S-0505-ESP-0158 (Comunidad de Madrid), University of Castilla-La Mancha, and CSIC (Nos. PI-200650I224 and PIF06-059 . A.M.M. acknowledges MCYT (Spanish Government) for a Ramón y Cajal Research Fellowship and CESGA for computing support. ; Peer reviewed

16 pages, 6 figures.-- ArXiv pre-print available at: http://arxiv.org/abs/physics/0608105 ; With the tools of lobe dynamics, the authors analyze the structures present in the velocity field obtained from a numerical simulation of the surface circulation in the northwestern Mediterranean Sea. In particular, focus is placed on the North Balearic Front, the westernmost part of the transition zone between saltier and fresher waters in the western Mediterranean, which is here interpreted in terms of the presence of a semipermanent "Lagrangian barrier," across which little transport occurs. Identified are relevant hyperbolic trajectories and their manifolds, and it is shown that the transport mechanism known as the turnstile, previously identified in abstract dynamical systems and simplified model flows, is also at work in this complex and realistic ocean flow. In addition, nonlinear dynamics techniques are shown to be powerful enough to identify the key geometric structures in this part of the Mediterranean. The construction also reveals the spatiotemporal routes along which this transport happens. Topological changes in that picture, which are associated with the crossing by eddies and may be interpreted as the breakdown of the front, are also observed during the simulation. ; A.M.M. acknowledges the MCyT (Spanish Government) for a Ramón y Cajal Research Fellowship and financial support from MEC (Spanish Government) reference MTM2004-00797 and the Royal Society-CSIC cooperation agreement reference B2003GB03. E.H.-G. acknowledges financial support from MEC and FEDER through Project CONOCE2 (FIS2004-00953). We also acknowledge M. Emelianov for communicating us results from a recent cruise before publication. D.S. and S. W. acknowledge financial support from ONR Grant No. N00014-01-1-0769. ; Peer reviewed

Recently, new steps have been taken for the development of operational applications in coastal areas which require very high resolutions both in modeling and remote sensing products. In this context, this work describes a complete monitoring of an oil spill: we discuss the performance of high resolution hydrodynamic models in the area of Gran Canaria and their ability for describing the evolution of a real-time event of a diesel fuel spill, well-documented by port authorities and tracked with very high resolution remote sensing products. Complementary information supplied by different sources enhances the description of the event and supports their validation. ; The authors acknowledge support from IMPRESSIVE, a project funded by the European Union's Horizon 2020 research and innovation programme under grant agreement No 821922. The authors acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). SW acknowledges the support of ONR Grant No. N00014-01-1-0769. ; Peer reviewed