Short-range atmosphere measurements under adverse weather conditions by using 265-nm LED mini-Lidar

Ordinary Lidars can observe as far away as several kilometers, however they cannot observe shot distance objects. The atmosphere near the ground is affected by the inequalities of ground, and they move very fast and complicatedly. To measure the low and surface atmosphere even during the daytime, we have developed a short range mini-Lidar using a deep ultraviolet LED with peak wavelength of 265 nm. Because sunlight falling on the ground does not contain light near 265 nm, the atmosphere can be observed in daytime with this mini-Lidar. This mini-lidar have a deep ultraviolet LED with a peak power of 50 mW and a repetition rate of 1 MHz. It can observe atmospheric echoes up to 100 m in the open air during the daytime. We report the concrete fabrication of this 265 nm LED based mini-Lidar and the measurements of short-range atmosphere during adverse weather condition. The developed mini-lidar was quite small (150 mm cube) and light weight (1.6 kg) enough to carried by hand. Artificial rain and fog measurements were carried in our experimental facility “Light Tunnel” under various adverse weather conditions (rain: 30 – 80 mm/h, fog: visibility under 10 m over a distance of 100 m). We clearly observed the rainfall amount in accordance with transmittance. We measured time variations of fog flow and its shading of density. On-site observations of the low and surface atmosphere with this 265 nm mini-Lidar were carried. Their airflow dynamics and activities are discussed.