The main purpose of eye-safe lidar ceilometers is regular reporting of cloud base height, vertical visibility, and cloud cover. These instruments operate unattended in harsh weather conditions. The application of state-of-the-art electronics increases the quality of backscatter profiles and thus qualifies modern ceilometers for the determination of boundary layer related parameters like the height of the mixing layer.

This paper concentrates on the Vaisala Ceilometer CL31. Its single lens optics that uses the inner part of the lens for transmitting and its outer part for receiving light improves near-range performance and allows the detection of nocturnal stable layers with heights not exceeding 50 m. The attached density plot shows a typical day with a high residual layer and low stable layers during nighttime, and the rise of the mixing layer driven by convection in the morning and noon hours. Layer heights are derived from local gradient minima.

An increasing number of meteorological services and environmental agencies are using the CL31 ceilometer for boundary layer monitoring. Examples from field campaigns performed by the Western Australia Department of Environment and Conservation, the Finnish Meteorological Institute, and the German Research Center Karlsruhe will be presented together with data collected by the research vessel Planet on a cruise from the Mediterranean to the Baltic Sea, demonstrating the use of ceilometers for marine applications. Available comparison sensors include wind profiler radar with RASS option, sodar, radio soundings, and aircraft temperature profiles.