Vaisala Ceilometer CL31 measures cloud base height and vertical visibility in all weather - good or bad. Backscatter profiling performance and reliability in all weather conditions up to 25,000 feet (7.6 km). It is a compact and lightweight instrument for cloud base height and vertical visibility measurements. It detects three cloud layers simultaneously. The CL31 employs a pulsed diode laser LIDAR (light detection and ranging) technology. The CL31 is ideal for aviation and meteorological applications.