SAR offshore wind fields in the Gulf of Lion

Krystallia Dimitriadou aDTU Wind and Energy Systems, DTU Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark

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Bjarke Tobias Olsen aDTU Wind and Energy Systems, DTU Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark

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Merete Badger aDTU Wind and Energy Systems, DTU Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark

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Charlotte Bay Hasager aDTU Wind and Energy Systems, DTU Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark

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Abstract

Offshore wind energy is rapidly growing due to high wind speeds and low visual impact at sea. In the North-Western Mediterranean, the Gulf of Lion is one area where floating offshore wind turbines will be installed. Detailed analysis of Synthetic Aperture Radar (SAR) scenes revealed wind flow patterns induced by coastal orography, such as flow channeling and horizontal lee waves, often unresolved in model wind fields, thus quantifying the local winds of Tramontane and Mistral. High-accuracy wind speeds retrieved at a 10 m level from satellite-borne SAR offer significant insight for wind resource estimation. Co-polarized SAR wind speed retrievals depend on wind direction input. Our motivation is to investigate the importance of reliable wind direction input in the SAR wind retrieval based one year of wind directions data from GFS, ERA5, and the New European Wind Atlas (NEWA). We validated against buoy data to assess their accuracy. While ERA5 showed the most accurate wind direction, this did not translate into high-precision SAR wind speeds. The three derived SAR wind speeds showed correlation coefficients of R2 between 0.90 (0.81) and 0.94 (0.84) against the Lyon (Begur) buoy datasets with best agreement being with ERA5 and NEWA in the Lion and Gebur buoys, respectively. These results suggest no preferred numerical model wind direction input for SAR retrievals.

© 2025 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Krystallia Dimitriadou, krstd@dtu.dk

Abstract

Offshore wind energy is rapidly growing due to high wind speeds and low visual impact at sea. In the North-Western Mediterranean, the Gulf of Lion is one area where floating offshore wind turbines will be installed. Detailed analysis of Synthetic Aperture Radar (SAR) scenes revealed wind flow patterns induced by coastal orography, such as flow channeling and horizontal lee waves, often unresolved in model wind fields, thus quantifying the local winds of Tramontane and Mistral. High-accuracy wind speeds retrieved at a 10 m level from satellite-borne SAR offer significant insight for wind resource estimation. Co-polarized SAR wind speed retrievals depend on wind direction input. Our motivation is to investigate the importance of reliable wind direction input in the SAR wind retrieval based one year of wind directions data from GFS, ERA5, and the New European Wind Atlas (NEWA). We validated against buoy data to assess their accuracy. While ERA5 showed the most accurate wind direction, this did not translate into high-precision SAR wind speeds. The three derived SAR wind speeds showed correlation coefficients of R2 between 0.90 (0.81) and 0.94 (0.84) against the Lyon (Begur) buoy datasets with best agreement being with ERA5 and NEWA in the Lion and Gebur buoys, respectively. These results suggest no preferred numerical model wind direction input for SAR retrievals.

© 2025 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Krystallia Dimitriadou, krstd@dtu.dk
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