DescriptionVaisala CL51 Ceilometer. Laser instrument that works in a single elastic channel at 910nm. Compared to the measurements of the other two systems, the CL51 measurements are less accurate and are more affected by noise, especially during the day. The advantage is that the CL51 works continuously, has a lower overlap height than that of the other lidar systems (around 150 meters) and offers data with a spatial resolution of 10 meters. The CL51 measurements are currently used for the determination of the height of the base of the clouds and the qualitative analysis of the evolution of the aerosols in the lower layers of the atmosphere.