Simultaneous observations of temperatures and ice-particles in the mid-latitude mesopause region

At the mid-latitude location of Kühlungsborn (54°N, 12°E) a number of noctilucent clouds (NLC) have been observed in the last years by ground-based lidars. Since 1997 up to five NLC per year have been detected (occurrence rate up to 12%), showing that the atmospheric conditions for NLC are fulfilled only occasionally at this location. The mean NLC altitude is 83.0 km and the mean NLC backscatter coefficient at 532 nm wavelength is about 2.5 × 10−10 m−1 sr−1. The combination of Rayleigh–Mie and potassium resonance lidar at our location enables additional temperature measurements in the mesosphere and lower thermosphere. In this configuration, the potassium lidar provides a simultaneously observed start temperature for the Rayleigh temperature calculation. We will demonstrate that this procedure avoids a bias in the upper range of the Rayleigh temperature profile (∼75–90 km) that especially in summer would often result in an overestimation of the true temperature. Within NLC direct temperature measurements are inhibited by observational constraints. We describe a method to use the Rayleigh backscatter profile for the temperature calculation at least above and below the NLC. We present temperature measurements during periods with supersaturation, that are partly but not always coupled with NLC. However, every observed NLC was found at the lower edge of the supersaturated range. Our observations show that at mid-latitudes NLC are not a tracer for temperatures below the frostpoint, as similar low temperatures occur both with and without NLC.