干旱区生态环境知识资源中心

In this work, a combined Raman-elastic backscatter lidar is described. It is based on a Q-switched powerful frequency-doubled Nd:YAG laser (output pulse power: up to 1 J at 1064 nm; up to 100 mJ at 532 nm; pulse duration 15 ns FWHM; repetition rate 2 Hz). A Cassegrain telescope (35 cm diameter, 200 cm focal length) collects backscattered radiation from atmospheric particles and molecules. Lidar's spectral receiving module consists of three cannels. The first two channels separate and detect elastic-backscattered lidar signals at laser wavelengths 1064 nm and 532 nm, respectively. In the third lidar channel, a radiation at a wavelength of 607 nm is selected and detected, resulting from Raman backscattering of laser second harmonic (532 nm) by atmospheric nitrogen molecules. Experimental profiles of the aerosol backscattering coefficient demonstrating measurement abilities of the system are shown and discussed. Particularly, attention is paid to profiles containing signals from high-altitude cirrus clouds, low-altitude stratus clouds, hazy atmospheric areas and Saharan dust over the city of Sofia.