Based on several case studies it is shown that clouds have a large impact on the mean and turbulent structure of the atmospheric boundary layer. This is shown by the analysis and comparison of results of data from different types of flight patterns. The data show clearly that turbulence is closely connected with radiation. Cloud top radiative cooling is redistributed by turbulence in the mixed layer. This is visible in different statistical moments of the turbulence, and often, e.g. a peak of the turbulent kinetic energy is measured within the clouds. As discussed in the talk, the detailed structure, depends on many parameters such as the atmospheric temperature and stability, the cloud optical thickness, wind speed and direction relative to the ice edge. Also surface roughness and the related wind shear are shaping profiles of turbulence moments. Finally, it is shown that the existence of multi-layer clouds is one of the most important factors for the turbulence structure of the lower atmospheric layers.