The equatorial surface velocity field derived from satellite altimeter observations

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The overall objective is to improve the current methods used to determine the equatorial surface velocity field. It is hoped that this will be of benefit to the Ocean SurfaceCurrent Analyses Real time (OSCAR) project and the Centre de Topographie des Oceans et del'Hydrosphµere (CTOH) product. Studies of the global surface velocity field provided by the OSCAR project and the CTOH product have shown that the velocities in the equatorial region, especially their meridional components, do not agree well with in situ observations. The main reason could be that the current methods used to calculate the velocity, which is related to SSH, are essentially based on geostrophic balance, although geostrophic balance breaks down in the equatorial region. This study will use a quasi-geostrophic model, which is based on the geostrophic balance relations, whereas its equatorial counterpart is based on different balance relations. These balance relations will be used in place of the geostrophic balance relations to determine the velocity that is related to SSH in the equatorial region. An ocean model will be used to investigate the properties of its equatorial SSH field, various algorithms that solve the proposed balance relations, the sensitivity with respect to parameter choices, and the accuracy of the results. Once a good understanding will have been developed about the best possible methods and their properties, the same investigation will be carried out with satellite altimeter observations, and additional issues such as errors investigated. The proposed project aims at improving the accuracy of global surface velocity field in the equatorial region. This thus improves its applicability to issues that it already helps to investigate, ranging from oil spills to the role of the horizontal advection on the surface heat budget. Improving the accuracy of the global surface velocity field will improve for instance the study of the surface heat budget, which in turn is relevant for climate studies. The project will also continue the educational activity of giving undergraduate and graduate students in the United States the opportunity to obtain an international research experience in coastal oceanography in East Africa.