Mid-latitude noctilucent cloud observations by lidar

Regular zenith-directed Rayleigh lidar soundings at Juliusruh (54.63 degrees N, 13.38 degrees E) in summer 1995 indicated the presence of overhead noctilucent clouds (NLC) during three nights in June. For two of these nights, NLC were also sighted visually near the northern horizon. For one of the lidar-observed NLC events, temperature profiles were obtained immediately prior to the appearance of the NLC. These show at 81 km a strong cooling of about 30 K within two hours. The wind velocity and direction during the NLC events were inferred from daytime common-volume MF radar wind measurements. During the occurrence of the NLCs the interpolated MF radar wind was south-westwards directed with velocities between 9 - 32 m/s. Different from high latitudes, NLCs can be observed by lidar at mid-latitudes in total darkness. Therefore, mid-latitude observations hold the promise to allow a characterisation of NLC particle size distributions and particle densities even with comparatively simple, multi-color lidars.