The models presented in Chaps.  4 and 5 outline the mean wind and turbulence in the atmospheric boundary layer under ideal conditions, i.e., horizontally uniform surfaces without obstacles and in steady-state scenarios. However, such ideal conditions are rarely encountered in reality, as the Earth’s surface is never completely flat and surface characteristics vary. This chapter explores the effects of heterogeneous and complex surfaces on wind and turbulence in the atmospheric boundary layer. Topics mainly include roughness change (Sect. 6.1), topographic effects (Sect. 6.2), urban boundary layer (Sect. 6.3), and marine boundary layer (Sect. 6.4). Given the significant impact of surface heterogeneity, it is essential to carefully consider this factor before conducting measurements in the atmospheric boundary layer.