CL31 measures cloud base height and vertical visibility. It can detect up to 5 different cloud layers from 0 to 7600 m (0 to 25 000 ft) at a resolution of 5 m (16 ft 5 in). CL31 is suitable for aviation purposes and meteorological applications where reliable detection of clouds is essential.
CL31 employs pulsed diode laser light detection and ranging (LIDAR) technology through single-lens optics, where short, powerful laser pulses are sent out in a vertical or near-vertical direction. The reflection of light (backscatter) caused by clouds, precipitation, or other obscuration is analyzed and used to determine the cloud base height. The cloud coverage algorithm in CL31 gathers cloud information from the last 30 minutes, updated at a 5‑minute interval. Cloud coverage is reported in 0–8 okta, according to WMO regulations.
An optional radiation shield provides better window protection during precipitation. In extreme temperatures, it protects against excessive heat or cooling. An automatic window blower with heater improves performance by keeping the window clean and dry. In cold conditions, heating prevents frost generation on the window.
CL31 is installed on the ground and connected to the weather station with a cable. When possible, you should prepare a concrete foundation and install CL31 on that. For additional information, see CL31 User Guide (M210482EN).