## 5 Summary-Outlook  
The study focused on the coastal effects in the German Bight, where numerous offshore wind farms are erected in the coastal zone. Statistical analysis of horizontal wind speed gradients with respect to winds blowing from the coast to the sea were performed. The study is solely based on the 10 m wind speed derived from SAR. Given the shape of the German Bight, predominant offshore winds are easterly, southerly and southerself winds. In order to enable the analysis of \"undisturbed\" wind speed gradients and its comparison with the potential influence of atmospheric wind farm wakes, the area around the wind farm cluster N-4 was chosen for the analysis. The focus of the study is on southerly and easterly winds, for which the wind direction is approximately perpendicular to the coastline. The investigations reveal that coastal effects are very pronounced in the German Bight. For both wind directions, and most of the cases (60%) a maximum relative and normalised wind speed increase about 2.6 m/s and 40% with growing distance from the coast is found. Also, large variations of the adjustment distance towards the equilibrium with maximum exceeding 170 km and an average of 67 km are showed. Overall, the horizontal wind speed gradients can be described by an exponential law. It was also shown that the wind speed increase in offshore direction is influenced by the thermal stability. The adjustment distance towards the equilibrium is longer for stable than for unstable stratification. The horizontal wind speed gradients are impacted by wakes, especially under stable stratification as these conditions are favorable for long wakes. Thus, strong gradient of horizontal wind downstream the cluster are found. Further investigations on the interaction between the wakes and the wind at the hub height and the internal boundary layer height are still needed. The location of the wind farm clusters with respect to the gradient of the wind speed can strongly affect the power production. Therefore, coastal effects need to be taken into account in the future planning of offshore wind farm installations. Differences between easterly and southerly wind directions with respect to the boundary layer adjustment length scale were discussed. It seems that the more rapid adjustment found for southerly wind directions is consistent with differences in the geometric shape of the coastline as well as with asymmetries of the boundary layer stability with respect to the wind direction. Further analysis is necessary to clarify the origin of this observation in more detail. Unusual horizontal wind speed gradient cases, i.e., wind speed decreases with growing distance from the coast are found. These situations appear to happen predominantly in stable atmospheric stratification. In addition, the LIDAR measurements reveal that this behaviour could be associated with the occurrence of LLJs. The situations with negative wind speed gradient require further investigations concerning the different physical processes involved. In particular, the 3D dynamics of the boundary layer including vertical profiles of wind, temperature and humidity, as well as vertical fluxes of momentum and heat require more analyses. This study largely focuses on the analysis of horizontal wind fields at near surface levels. It has certainly limitations regarding insights into processes at higher altitudes and the structure of the internal boundary layer. The combination of SAR data with 3D model simulations (e.g., Weather Research and Forecasting (WRF)) or 3D reanalysis data (e.g., ERA5) could be an interesting approach to improve the process understanding in subsequent studies. The coastal effects are of particular relevance for offshore wind energy, as the wind farms are mostly located in the complex transition area between the land and the ocean boundary layer. The optimal layout of a windfarm, e.g., the turbine spacing is a complicated problem even in a homogeneous boundary layer in equilibrium [66].