Correcting surface winds by assimilating high-frequency radar surface currents in the German Bight
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Surface winds are crucial for accurately modeling the surface circulation in the coastal ocean. In the present work, high-frequency radar surface currents are assimilated using an ensemble scheme which aims to obtain improved surface winds taking into account European Centre for Medium-Range Weather Forecasts winds as a first guess and surface current measurements. The objective of this study is to show that wind forcing can be improved using an approach similar to parameter estimation in ensemble data assimilation. Like variational assimilation schemes, the method provides an improved wind field based on surface current measurements. However, the technique does not require an adjoint, and it is thus easier to implement. In addition, it does not rely on a linearization of the model dynamics. The method is validated directly by comparing the analyzed wind speed to independent in situ measurements and indirectly by assessing the impact of the corrected winds on model sea surface temperature (SST) relative to satellite SST.
KeywordsData assimilation Ensemble simulation High-frequency radar Surface currents
Klaus-Werner Gurgel from the University of Hamburg is thanked for providing the HF radar observations. The National Fund for Scientific Research, Belgium is acknowledged for funding the post-doctoral positions of the two first authors. This work was supported by the ECOOP project (European Coastal-shelf sea Operational observing and forecasting system) of the European Union. AVHRR Oceans Pathfinder SST data were obtained through the online PO.DAAC Ocean ESIP Tool (POET) at the Physical Oceanography Distributed Active Archive Center (PO.DAAC), NASA Jet Propulsion Laboratory, Pasadena, CA (http://podaac.jpl.nasa.gov/poet). Wind observations were obtained through the Web-based Weather Request and Distribution System from the German Meteorological Service (Deutscher Wetterdienst). We thank also two anonymous referees for their valuable comments and their constructive suggestions. This is a MARE publication.
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