Sea surface wind field retrieval from TerraSAR-X and its applications to coastal areas

In the present study, development of the new Geophysical Model Function (GMF) XMOD2 to derive the sea surface wind speed from the TerraSAR-X data is described. The XMOD2 has the similar model functions as the CMOD5 for the bias term B₀ and upwind/cross-wind term B₂, while the upwind/downwind term B₁ is adjusted based on the sea surface backscatter properties of the TerraSAR-X. Coefficients of the XMOD2 are tuned using the collocations of TerraSAR-X measurements with in situ buoy measurements and results of the atmospheric model. By comparing the retrieved sea surface wind speed using XMOD2 to in situ buoy measurements, good agreement is achieved with a bias of 0.07 m/s and an RMSE of 1.57 m/s. We presented a case study of mapping the sea surface wind field over the offshore wind farming Alpha Ventus over the North Sea to demonstrate the application of TerraSAR-X data to investigate the significant spatial variations of the sea surface wind field in the offshore wind farm sites.