Estimation of wind fields in the German Bight from ERS-1 SAR images

SAR images acquired over the German Bight are used to estimate wind fields over open water. The wind speed is derived from the the normalized radar cross section of the sea surface by applying a backscatter model to the SAR images which was originally developed for wind vector retrieval from ERS scatterometer data (CMOD4). Because of the unique topography of the German coast with its wadden flats, shoals and small islands this well established method does not provide reliable wind field estimations in all parts of the water surface. Therefore the image is segmented using a texture based algorithm. Calculating the average wind speed for each segment and comparing it to wind speed data recorded by weather stations reveals areas with values of the NRCS which can not exclusively be related to the wind field. An influence of the the sea bottom topography has to be considered