The higher wind power available offshore is caused by differences of mechanical and thermodynamic properties of the ocean and the land. Over a big patch of homogeneous ocean or land surface one can usually find an atmospheric boundary layer, which is in an approximate equilibrium with respect to pressure gradients, frictional forces and the Coriolis force. However, in coastal areas, where most of the existing offshore wind farms are located, a complex transition process occurs between the land and the ocean boundary layer. This phenomenon is of particular interest for offshore wind directions, where an internal boundary layer (IBL) forms downstream of the land boundary. The three-dimensional (3D) dynamics of the atmosphere in this transition zone is complicated and constitutes a challenge for numerical forecasting for different reasons. Firstly, there is usually insufficient information about roughness properties of the land surface, and the sea surface roughness is affected by ocean surface waves, which have a complex dynamics by themselves. Secondly, the formation of the IBL is strongly conditioned by the 3D dynamics of turbulence (e.g., horizontal advection), which is still a challenge for atmospheric models as well. Thirdly, the stability of the boundary layer is affected by the sea surface temperature in the transition region. These temperatures often show horizontal gradients related to changes in water depths, which are still difficult to capture accurately by either satellites or numerical ocean models. As the representation of coastal effects in numerical models is still challenging, measurements are important to improve the understanding and the prediction of the respective processes [5; 6]. The importance of thermal effects and sea surface roughness was investigated in a number of previous studies [7; 8; 9]. The role of advection processes in the land-sea transition region and their relevance for offshore wind farms was discussed in [PERSON] et al. [10]. Large Eddy Simulations (LES) were used in [PERSON] et al. [11] to study the dependence of wind power available to a wind farm on the distance from the shoreline. In this study, satellite synthetic aperture radar (SAR) data are used to analyse coastal effects and the potential impacts on offshore wind farms are briefly discussed. SAR data provide information on near surface wind speeds over the ocean with high spatial resolution (e.g., 400 m) and are independent of cloud or daylight conditions [12; 13]. These data are therefore well suited to study the spatial evolution of the wind field from land towards the sea under different atmospheric conditions. SAR data have already been used in the offshore wind context in several previous studies [13; 14; 15; 16; 17; 18]. [PERSON] et al. [19] looked at coastal wind speed gradients at the Danish coast with SAR as well, although the focus of their study was on in-situ and model data analysis. More detailed discussions of shapes of horizontal wind speed gradients or dependencies on stability of the boundary layer were not given. The main objective of this study is to analyse the shape of the horizontal wind speed gradients derived from SAR datasets and the respective dependence on the stability of the atmospheric boundary layer in OWF areas. Furthermore, the goal is to condense the SAR information into an empirical model for the coastal effect, which can be used as a reference in subsequent studies. The study is focused on the German Bight, which is a particularly interesting region to study coastal effects, because the mirrored L-shaped form of the coastline leads to offshore wind directions for both easterly and southerly winds. A characteristic of the German Bight is the very shallow water depth with a maximum of about 50 m and Wadden Sea areas, which are periodically falling dry following the dominant M2 tidal component with 12.42 h period [20; 21]. Also, the shape of the coastline is complicated by the east Frisian and north Frisian barrier islands, as well as various ways.