To conclude the international field experiment COPS (Convective and Orograpically-induced Precipitation Study) in June-August 2007 a special issue of the Quarterly Journal of the Royal Meteorological Society has appeared. The Institute was involved with the POLDIRAD radar and the combination of water vapour and wind lidars on the Falcon research aircraft in this experiment. Core goal of COPS is to improve the precipitation forecast over low mountain ranges that are affected by large losses from floods, hail damage, etc. In particular, the models underestimate precipitation in the lee of the mountains. The radar results show inter alia a clear correlation between the strength of the mountain flow and the origin of thunderstorms: strong currents shift the storm from the main ridge to the lee-side. This observation allows us to verify and improve models. The new water vapour lidar WALES was for the first time successfully operated to quantify the horizontal transport of water vapour into the COPS region, and to determine the vertical transport in a turbulent boundary layer over low mountain ranges. This was not possible so far.