In all European countries with shallow coastal waters and strong mean wind speed at the coast the planning and construction of offshore wind farms is on the way and large parts of the North Sea and the Baltic are under investigation as to whether they are suitable for offshore parks. In this paper it is demonstrated how satellite images taken by spaceborne radar sensors can be used to determine mesoscale wind fields and thus help in the task of planning offshore wind farms. High resolution SAR (Synthetic Aperture Radar) images acquired by the European remote sensing satellite ERS 2 are presented which show single wind turbines. The derivation of high resolution wind fields from SAR images is explained and comparisons with numerical models are presented.
During the past two decades weather forecast has greatly improved due to the consideration of geophysical parameters derived from remote sensing data. Instruments operating in the optical and infrared regime, e.g. from the geostationary satellites METEOSAT and GOES, are used for retrieval of cloud parameters, which are assimilated into the weather forecast models. Data from active microwave radar satellites transmit and receive radar signals with wavelengths in the range of centimeters to one meter and measure the roughness of the sea surface, which allows to retrieve wind or ocean wave fields. As the radar signals penetrate clouds these sensors have all weather capability and can acquire data at day and nighttime and are therefore especially suited for sea surface observations during severe weather condition. In Fig. 1 a SAR image of the German Bight of the North Sea acquired aboard ERS-2 is shown. In the lee of Heligoland a turbulent wake generated by the island can be seen that extends from the island to shore (~40 km).