My research topics covers -Understanding the physical processes that govern fog. -Stable Boundary Layers -Evaluation and understanding model behavior of the boundary layer schemes in the mesoscale model WRF. -Urban meteorology. My previous research mainly focussed on understanding the stable boundary layer over land. At night and in wintertime, the near surface atmosphere becomes stably stratified, i.e. the temperature increases with height. As a result of the stratification, turbulent transport is suppressed, and may even vanish for low wind speeds. In that case other processes than turbulence, e.g. radiation divergence, drainage flows, gravity waves take over the stable boundary-layer development. This complexity hampers model development and therefore model skill for the stable boundary layer is rather poor. To improve this, detailed column model studies has been done based on the CASES-99 experiment. We learnt the stable boundary layer can be well modelled from a local perspective if sufficient resolution, correct forcings and land use properties are prescribed. This is currently further studied in the GABLS experiment. Moreover, within the I partcipate in the HYDRALABIII experiment in order to understand turbulent mixing in stratified flows under more controlled conditions than in the atmosphere. Also, I partcipated in the PILPS-URBAN model intercomparison, in which urban land surface schemes were evaluated against observations.