A broad suite of ground-based remote sensing instruments of the Meteorological Observatory Lindenberg, Germany, is combined for the first time to synergistically analyze cirrus cloud microphysics, including a Raman lidar, a Ka band cloud radar and a 5ff tilted ceilometer. 84 days of cirrus cloud measurements have been selected to study the correlation between, and the dependences of, the different measured variables. The presented study investigates the effect of the spatial orientation and the shape of solid cloud particles on particle optical properties and their relation to wind and turbulence parameters. A sensitive indicator of particle spatial orientation is the particle depolarization ratio (PDR). When ice crystals are horizontally aligned, mirror reflections can occur, which is evidenced by low PDR if observed with a vertically pointing Raman lidar. Observations are grouped according to the prevailing weather condition. It is found that on some days PDR is constant for long time periods. Interestingly, during warm fronts the PDR is generally small (<0.2), while during cold fronts it is high (> 0.4). Moreover, the mean lidar ratio of cirrus with high PDR is about 20 sr, two times larger than of cirrus with low PDR. Similar dependences on PDR have been found for the particle extinction coefficient, and for the backscatter coefficient from the tilted ceilometer, but for the Raman lidar backscatter coefficient in perpendicular polarization the opposite behavior is observed.
Since 2005, the high-performance multiparameter Raman lidar RAMSES (Raman lidar for atmospheric moisture sensing) for water vapor, temperature, cloud and aerosol measurements is part of the broad suite of active and passive remote-sensing instruments monitoring the atmosphere at the German Meteorological Services observatory in Lindenberg. Initially housed in a 20-foot container, continued expansion of RAMSES made accommodation of the instrument increasingly difficult, and caused problems in air-conditioning. For these reasons, a new lidar facility was built on site in 2013. It is now home to RAMSES, and it also provides extra laboratory space for (lidar) experiments. The Lindenberg lidar facility is described in detail. One of its features is the precision air-conditioning system which is designed to keep the temperature field of the RAMSES room stable within 1 K at all times. Migration from the container to the new building offered an opportunity to make changes to the RAMSES instrument itself. For instance, stray light suppression was further improved, selection of photomultiplier tubes was optimized, and the near-range receiver was redesigned to enhance its daytime capabilities. Further, in addition to the water spectrometer for calibrated measurements of cloud Raman backscatter-coefficient spectra, a second spectrometer was implemented for studies of the fluorescence spectra of atmospheric aerosols. At the conference, these technical modifications are discussed, and first measurement examples with the improved lidar are presented.