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Parameterizing the effect of vertically-distributed vegetation through an effective roughness (z0,eff) – whereby momentum loss through a three-dimensional foliage volume is represented as momentum loss over an area at one vertical level – can facilitate the use of forest data in flow models, to any level of detail, and simultaneously reduce computational cost. Results of numerical experiments and comparison with observations show that a modelling approach based on z0,eff can estimate wind speed and turbulence levels over forested areas, at heights of interest for wind energy applications (∼60 m and higher), but only above flat terrain. Caution must be exercised in the application of such a model to zones of forest edges. Advanced flow models capable of incorporating local (distributed) drag forces are recommended for complex terrain covered by forest.

Offshore wind energy use is commonly suggested to play an important role in future electricity supply. However, long-term experience with thousands of onshore wind turbines explicitly hint on possible barriers for a safe, efficient, economic and user friendly supply relying on offshore wind energy. A national German programme shall on the one hand support the wind energy sector improving technology and O&M procedures towards higher reliability and availability, and on the other hand monitor the development in terms of techniques, electricity yields and cost. In the following, this scientific monitoring programme, the ‘Offshore∼WMEP’, is presented. The actual challenge of this programme is to convince numerous players with diverse points of interest to collaborate in gathering data and providing it for a jointly utilized database.